Documentation/kbuild/kconfig-language.txt warns to use select with care, and in general use select only for non-visible symbols and for symbols with no dependencies, because select will force a symbol to a value without visiting the dependencies.
Select has become particularly problematic, interdependently, with the BACKLIGHT_CLASS_DEVICE and ACPI_VIDEO configs. For example:
scripts/kconfig/conf --randconfig Kconfig KCONFIG_SEED=0x48312B00 warning: (DRM_RADEON && DRM_NOUVEAU && DRM_I915 && DRM_GMA500 && DRM_SHMOBILE && DRM_TILCDC && FB_BACKLIGHT && FB_MX3 && USB_APPLEDISPLAY && FB_OLPC_DCON && ASUS_LAPTOP && SONY_LAPTOP && THINKPAD_ACPI && EEEPC_LAPTOP && ACPI_CMPC && SAMSUNG_Q10) selects BACKLIGHT_CLASS_DEVICE which has unmet direct dependencies (HAS_IOMEM && BACKLIGHT_LCD_SUPPORT) warning: (DRM_RADEON && DRM_NOUVEAU && DRM_I915 && DRM_GMA500 && DRM_SHMOBILE && DRM_TILCDC && FB_BACKLIGHT && FB_MX3 && USB_APPLEDISPLAY && FB_OLPC_DCON && ASUS_LAPTOP && SONY_LAPTOP && THINKPAD_ACPI && EEEPC_LAPTOP && ACPI_CMPC && SAMSUNG_Q10) selects BACKLIGHT_CLASS_DEVICE which has unmet direct dependencies (HAS_IOMEM && BACKLIGHT_LCD_SUPPORT)
With tristates it's possible to end up selecting FOO=y depending on BAR=m in the config, which gets discovered at build time, not config time, like reported in the thread referenced below.
Do the following to fix the dependencies:
* Depend on instead of select BACKLIGHT_CLASS_DEVICE everywhere. Drop select BACKLIGHT_LCD_SUPPORT in such cases, as it's a dependency of BACKLIGHT_CLASS_DEVICE.
* Remove config FB_BACKLIGHT altogether, and replace it with a dependency on BACKLIGHT_CLASS_DEVICE. All configs selecting FB_BACKLIGHT select or depend on FB anyway, so we can simplify.
* Depend on (ACPI && ACPI_VIDEO) || ACPI=n in several places instead of selecting ACPI_VIDEO and a number of its dependencies if ACPI is enabled. This is tied to backlight, as ACPI_VIDEO depends on BACKLIGHT_CLASS_DEVICE.
* Replace a couple of select INPUT/VT with depends as it seemed to be necessary.
Reference: http://lkml.kernel.org/r/CA+r1ZhhmT4DrWtf6MbRQo5EqXwx+LxCqh15Vsu_d9WpftLhnxw... Reported-by: Jim Davis jim.epost@gmail.com Cc: Randy Dunlap rdunlap@infradead.org Cc: David Airlie airlied@linux.ie Cc: Daniel Vetter daniel.vetter@intel.com Cc: Greg Kroah-Hartman gregkh@linuxfoundation.org Cc: Darren Hart dvhart@infradead.org Cc: Laurent Pinchart laurent.pinchart@ideasonboard.com Cc: Benjamin Herrenschmidt benh@kernel.crashing.org Cc: Jens Frederich jfrederich@gmail.com Cc: Daniel Drake dsd@laptop.org Cc: Jon Nettleton jon.nettleton@gmail.com Cc: Jean-Christophe Plagniol-Villard plagnioj@jcrosoft.com Cc: Tomi Valkeinen tomi.valkeinen@ti.com Signed-off-by: Jani Nikula jani.nikula@intel.com
---
Sorry for the huge distribution; this is really quite hard to split up sensibly without breaking the build! --- drivers/gpu/drm/Kconfig | 2 +- drivers/gpu/drm/gma500/Kconfig | 4 +--- drivers/gpu/drm/i915/Kconfig | 9 ++------- drivers/gpu/drm/nouveau/Kconfig | 10 ++-------- drivers/gpu/drm/shmobile/Kconfig | 2 +- drivers/gpu/drm/tilcdc/Kconfig | 3 +-- drivers/macintosh/Kconfig | 2 +- drivers/platform/x86/Kconfig | 19 ++++++++----------- drivers/staging/olpc_dcon/Kconfig | 2 +- drivers/usb/misc/Kconfig | 3 +-- drivers/video/fbdev/Kconfig | 29 +++++++++++------------------ drivers/video/fbdev/core/fbsysfs.c | 8 ++++---- include/linux/fb.h | 2 +- include/uapi/linux/fb.h | 2 +- 14 files changed, 36 insertions(+), 61 deletions(-)
diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig index e3b4b0f02b3d..dc789d0e293c 100644 --- a/drivers/gpu/drm/Kconfig +++ b/drivers/gpu/drm/Kconfig @@ -99,6 +99,7 @@ config DRM_R128 config DRM_RADEON tristate "ATI Radeon" depends on DRM && PCI + depends on BACKLIGHT_CLASS_DEVICE || BACKLIGHT_CLASS_DEVICE=n select FB_CFB_FILLRECT select FB_CFB_COPYAREA select FB_CFB_IMAGEBLIT @@ -108,7 +109,6 @@ config DRM_RADEON select DRM_TTM select POWER_SUPPLY select HWMON - select BACKLIGHT_CLASS_DEVICE select INTERVAL_TREE select MMU_NOTIFIER help diff --git a/drivers/gpu/drm/gma500/Kconfig b/drivers/gpu/drm/gma500/Kconfig index 17f928ec84ea..a84d0a4fcc58 100644 --- a/drivers/gpu/drm/gma500/Kconfig +++ b/drivers/gpu/drm/gma500/Kconfig @@ -8,9 +8,7 @@ config DRM_GMA500 select DRM_KMS_FB_HELPER select DRM_TTM # GMA500 depends on ACPI_VIDEO when ACPI is enabled, just like i915 - select ACPI_VIDEO if ACPI - select BACKLIGHT_CLASS_DEVICE if ACPI - select INPUT if ACPI + depends on (ACPI && ACPI_VIDEO) || ACPI=n help Say yes for an experimental 2D KMS framebuffer driver for the Intel GMA500 ('Poulsbo') and other Intel IMG based graphics diff --git a/drivers/gpu/drm/i915/Kconfig b/drivers/gpu/drm/i915/Kconfig index 4e39ab34eb1c..75d4c52c0971 100644 --- a/drivers/gpu/drm/i915/Kconfig +++ b/drivers/gpu/drm/i915/Kconfig @@ -3,6 +3,8 @@ config DRM_I915 depends on DRM depends on X86 && PCI depends on (AGP || AGP=n) + depends on (ACPI && ACPI_VIDEO) || ACPI=n + depends on BACKLIGHT_CLASS_DEVICE || BACKLIGHT_CLASS_DEVICE=n select INTEL_GTT select AGP_INTEL if AGP select INTERVAL_TREE @@ -11,13 +13,6 @@ config DRM_I915 select SHMEM select TMPFS select DRM_KMS_HELPER - # i915 depends on ACPI_VIDEO when ACPI is enabled - # but for select to work, need to select ACPI_VIDEO's dependencies, ick - select BACKLIGHT_LCD_SUPPORT if ACPI - select BACKLIGHT_CLASS_DEVICE if ACPI - select INPUT if ACPI - select ACPI_VIDEO if ACPI - select ACPI_BUTTON if ACPI help Choose this option if you have a system that has "Intel Graphics Media Accelerator" or "HD Graphics" integrated graphics, diff --git a/drivers/gpu/drm/nouveau/Kconfig b/drivers/gpu/drm/nouveau/Kconfig index 40afc69a3778..40227fc4f284 100644 --- a/drivers/gpu/drm/nouveau/Kconfig +++ b/drivers/gpu/drm/nouveau/Kconfig @@ -1,6 +1,7 @@ config DRM_NOUVEAU tristate "Nouveau (NVIDIA) cards" depends on DRM && PCI + depends on (ACPI && ACPI_VIDEO) || ACPI=n select FW_LOADER select DRM_KMS_HELPER select DRM_KMS_FB_HELPER @@ -10,18 +11,10 @@ config DRM_NOUVEAU select FB_CFB_IMAGEBLIT select FB select FRAMEBUFFER_CONSOLE if !EXPERT - select FB_BACKLIGHT if DRM_NOUVEAU_BACKLIGHT - select ACPI_VIDEO if ACPI && X86 && BACKLIGHT_CLASS_DEVICE && INPUT select X86_PLATFORM_DEVICES if ACPI && X86 select ACPI_WMI if ACPI && X86 select MXM_WMI if ACPI && X86 select POWER_SUPPLY - # Similar to i915, we need to select ACPI_VIDEO and it's dependencies - select BACKLIGHT_LCD_SUPPORT if ACPI && X86 - select BACKLIGHT_CLASS_DEVICE if ACPI && X86 - select INPUT if ACPI && X86 - select THERMAL if ACPI && X86 - select ACPI_VIDEO if ACPI && X86 help Choose this option for open-source NVIDIA support.
@@ -64,6 +57,7 @@ config NOUVEAU_DEBUG_DEFAULT config DRM_NOUVEAU_BACKLIGHT bool "Support for backlight control" depends on DRM_NOUVEAU + depends on BACKLIGHT_CLASS_DEVICE default y help Say Y here if you want to control the backlight of your display diff --git a/drivers/gpu/drm/shmobile/Kconfig b/drivers/gpu/drm/shmobile/Kconfig index a50fe0eeaa0d..71c00f3c0fbc 100644 --- a/drivers/gpu/drm/shmobile/Kconfig +++ b/drivers/gpu/drm/shmobile/Kconfig @@ -2,7 +2,7 @@ config DRM_SHMOBILE tristate "DRM Support for SH Mobile" depends on DRM && ARM depends on ARCH_SHMOBILE || COMPILE_TEST - select BACKLIGHT_CLASS_DEVICE + depends on BACKLIGHT_CLASS_DEVICE select DRM_KMS_HELPER select DRM_KMS_FB_HELPER select DRM_KMS_CMA_HELPER diff --git a/drivers/gpu/drm/tilcdc/Kconfig b/drivers/gpu/drm/tilcdc/Kconfig index 7c3ef79fcb37..52e60feaae53 100644 --- a/drivers/gpu/drm/tilcdc/Kconfig +++ b/drivers/gpu/drm/tilcdc/Kconfig @@ -1,13 +1,12 @@ config DRM_TILCDC tristate "DRM Support for TI LCDC Display Controller" depends on DRM && OF && ARM + depends on BACKLIGHT_CLASS_DEVICE select DRM_KMS_HELPER select DRM_KMS_FB_HELPER select DRM_KMS_CMA_HELPER select DRM_GEM_CMA_HELPER select VIDEOMODE_HELPERS - select BACKLIGHT_CLASS_DEVICE - select BACKLIGHT_LCD_SUPPORT help Choose this option if you have an TI SoC with LCDC display controller, for example AM33xx in beagle-bone, DA8xx, or diff --git a/drivers/macintosh/Kconfig b/drivers/macintosh/Kconfig index 3067d56b11a6..50cb2c3b567e 100644 --- a/drivers/macintosh/Kconfig +++ b/drivers/macintosh/Kconfig @@ -135,7 +135,7 @@ config PMAC_MEDIABAY config PMAC_BACKLIGHT bool "Backlight control for LCD screens" depends on ADB_PMU && FB = y && (BROKEN || !PPC64) - select FB_BACKLIGHT + depends on BACKLIGHT_CLASS_DEVICE help Say Y here to enable Macintosh specific extensions of the generic backlight code. With this enabled, the brightness keys on older diff --git a/drivers/platform/x86/Kconfig b/drivers/platform/x86/Kconfig index 4dcfb7116a04..63e99ce0e3f8 100644 --- a/drivers/platform/x86/Kconfig +++ b/drivers/platform/x86/Kconfig @@ -17,7 +17,7 @@ if X86_PLATFORM_DEVICES
config ACER_WMI tristate "Acer WMI Laptop Extras" - depends on ACPI + depends on ACPI && ACPI_VIDEO select LEDS_CLASS select NEW_LEDS depends on BACKLIGHT_CLASS_DEVICE @@ -26,8 +26,6 @@ config ACER_WMI depends on RFKILL || RFKILL = n depends on ACPI_WMI select INPUT_SPARSEKMAP - # Acer WMI depends on ACPI_VIDEO when ACPI is enabled - select ACPI_VIDEO if ACPI ---help--- This is a driver for newer Acer (and Wistron) laptops. It adds wireless radio and bluetooth control, and on some laptops, @@ -70,7 +68,7 @@ config ASUS_LAPTOP depends on ACPI select LEDS_CLASS select NEW_LEDS - select BACKLIGHT_CLASS_DEVICE + depends on BACKLIGHT_CLASS_DEVICE depends on INPUT depends on RFKILL || RFKILL = n select INPUT_SPARSEKMAP @@ -294,7 +292,7 @@ config COMPAL_LAPTOP config SONY_LAPTOP tristate "Sony Laptop Extras" depends on ACPI - select BACKLIGHT_CLASS_DEVICE + depends on BACKLIGHT_CLASS_DEVICE depends on INPUT depends on RFKILL ---help--- @@ -329,8 +327,7 @@ config THINKPAD_ACPI depends on ACPI depends on INPUT depends on RFKILL || RFKILL = n - select BACKLIGHT_LCD_SUPPORT - select BACKLIGHT_CLASS_DEVICE + depends on BACKLIGHT_CLASS_DEVICE select HWMON select NVRAM select NEW_LEDS @@ -499,7 +496,7 @@ config EEEPC_LAPTOP depends on INPUT depends on RFKILL || RFKILL = n depends on HOTPLUG_PCI - select BACKLIGHT_CLASS_DEVICE + depends on BACKLIGHT_CLASS_DEVICE select HWMON select LEDS_CLASS select NEW_LEDS @@ -675,8 +672,8 @@ config ACPI_CMPC tristate "CMPC Laptop Extras" depends on X86 && ACPI depends on RFKILL || RFKILL=n - select INPUT - select BACKLIGHT_CLASS_DEVICE + depends on INPUT + depends on BACKLIGHT_CLASS_DEVICE default n help Support for Intel Classmate PC ACPI devices, including some @@ -805,7 +802,7 @@ config INTEL_OAKTRAIL config SAMSUNG_Q10 tristate "Samsung Q10 Extras" depends on ACPI - select BACKLIGHT_CLASS_DEVICE + depends on BACKLIGHT_CLASS_DEVICE ---help--- This driver provides support for backlight control on Samsung Q10 and related laptops, including Dell Latitude X200. diff --git a/drivers/staging/olpc_dcon/Kconfig b/drivers/staging/olpc_dcon/Kconfig index d277f048789e..94acb4279704 100644 --- a/drivers/staging/olpc_dcon/Kconfig +++ b/drivers/staging/olpc_dcon/Kconfig @@ -3,7 +3,7 @@ config FB_OLPC_DCON depends on OLPC && FB depends on I2C depends on (GPIO_CS5535 || GPIO_CS5535=n) - select BACKLIGHT_CLASS_DEVICE + depends on BACKLIGHT_CLASS_DEVICE ---help--- In order to support very low power operation, the XO laptop uses a secondary Display CONtroller, or DCON. This secondary controller diff --git a/drivers/usb/misc/Kconfig b/drivers/usb/misc/Kconfig index 76d77206e011..824630b09662 100644 --- a/drivers/usb/misc/Kconfig +++ b/drivers/usb/misc/Kconfig @@ -150,8 +150,7 @@ config USB_FTDI_ELAN
config USB_APPLEDISPLAY tristate "Apple Cinema Display support" - select BACKLIGHT_LCD_SUPPORT - select BACKLIGHT_CLASS_DEVICE + depends on BACKLIGHT_CLASS_DEVICE help Say Y here if you want to control the backlight of Apple Cinema Displays over USB. This driver provides a sysfs interface. diff --git a/drivers/video/fbdev/Kconfig b/drivers/video/fbdev/Kconfig index ccbe2ae22ac5..8cae7da2c723 100644 --- a/drivers/video/fbdev/Kconfig +++ b/drivers/video/fbdev/Kconfig @@ -185,13 +185,6 @@ config FB_MACMODES depends on FB default n
-config FB_BACKLIGHT - bool - depends on FB - select BACKLIGHT_LCD_SUPPORT - select BACKLIGHT_CLASS_DEVICE - default n - config FB_MODE_HELPERS bool "Enable Video Mode Handling Helpers" depends on FB @@ -323,7 +316,7 @@ config FB_CLPS711X tristate "CLPS711X LCD support" depends on FB && (ARCH_CLPS711X || COMPILE_TEST) select FB_CLPS711X_OLD if ARCH_CLPS711X && !ARCH_MULTIPLATFORM - select BACKLIGHT_LCD_SUPPORT + depends on BACKLIGHT_LCD_SUPPORT select FB_MODE_HELPERS select FB_SYS_FILLRECT select FB_SYS_COPYAREA @@ -351,7 +344,7 @@ config FB_SA1100 config FB_IMX tristate "Freescale i.MX1/21/25/27 LCD support" depends on FB && ARCH_MXC - select BACKLIGHT_LCD_SUPPORT + depends on BACKLIGHT_LCD_SUPPORT select LCD_CLASS_DEVICE select FB_CFB_FILLRECT select FB_CFB_COPYAREA @@ -674,7 +667,7 @@ config FB_STI select FB_CFB_COPYAREA select FB_CFB_IMAGEBLIT select STI_CONSOLE - select VT + depends on VT default y ---help--- STI refers to the HP "Standard Text Interface" which is a set of @@ -990,7 +983,7 @@ config FB_S1D13XXX config FB_ATMEL tristate "AT91/AT32 LCD Controller support" depends on FB && HAVE_FB_ATMEL - select FB_BACKLIGHT + depends on BACKLIGHT_CLASS_DEVICE select FB_CFB_FILLRECT select FB_CFB_COPYAREA select FB_CFB_IMAGEBLIT @@ -1019,7 +1012,6 @@ config FB_ATMEL_STN config FB_NVIDIA tristate "nVidia Framebuffer Support" depends on FB && PCI - select FB_BACKLIGHT if FB_NVIDIA_BACKLIGHT select FB_MODE_HELPERS select FB_CFB_FILLRECT select FB_CFB_COPYAREA @@ -1060,6 +1052,7 @@ config FB_NVIDIA_DEBUG config FB_NVIDIA_BACKLIGHT bool "Support for backlight control" depends on FB_NVIDIA + depends on BACKLIGHT_CLASS_DEVICE default y help Say Y here if you want to control the backlight of your display. @@ -1067,7 +1060,6 @@ config FB_NVIDIA_BACKLIGHT config FB_RIVA tristate "nVidia Riva support" depends on FB && PCI - select FB_BACKLIGHT if FB_RIVA_BACKLIGHT select FB_MODE_HELPERS select FB_CFB_FILLRECT select FB_CFB_COPYAREA @@ -1107,6 +1099,7 @@ config FB_RIVA_DEBUG config FB_RIVA_BACKLIGHT bool "Support for backlight control" depends on FB_RIVA + depends on BACKLIGHT_CLASS_DEVICE default y help Say Y here if you want to control the backlight of your display. @@ -1345,7 +1338,6 @@ config FB_MATROX_MAVEN config FB_RADEON tristate "ATI Radeon display support" depends on FB && PCI - select FB_BACKLIGHT if FB_RADEON_BACKLIGHT select FB_MODE_HELPERS select FB_CFB_FILLRECT select FB_CFB_COPYAREA @@ -1370,6 +1362,7 @@ config FB_RADEON_I2C config FB_RADEON_BACKLIGHT bool "Support for backlight control" depends on FB_RADEON + depends on BACKLIGHT_CLASS_DEVICE default y help Say Y here if you want to control the backlight of your display. @@ -1389,7 +1382,6 @@ config FB_ATY128 select FB_CFB_FILLRECT select FB_CFB_COPYAREA select FB_CFB_IMAGEBLIT - select FB_BACKLIGHT if FB_ATY128_BACKLIGHT select FB_MACMODES if PPC_PMAC help This driver supports graphics boards with the ATI Rage128 chips. @@ -1402,6 +1394,7 @@ config FB_ATY128 config FB_ATY128_BACKLIGHT bool "Support for backlight control" depends on FB_ATY128 + depends on BACKLIGHT_CLASS_DEVICE default y help Say Y here if you want to control the backlight of your display. @@ -1412,7 +1405,6 @@ config FB_ATY select FB_CFB_FILLRECT select FB_CFB_COPYAREA select FB_CFB_IMAGEBLIT - select FB_BACKLIGHT if FB_ATY_BACKLIGHT select FB_MACMODES if PPC help This driver supports graphics boards with the ATI Mach64 chips. @@ -1452,6 +1444,7 @@ config FB_ATY_GX config FB_ATY_BACKLIGHT bool "Support for backlight control" depends on FB_ATY + depends on BACKLIGHT_CLASS_DEVICE default y help Say Y here if you want to control the backlight of your display. @@ -1997,12 +1990,12 @@ config FB_SH_MOBILE_LCDC tristate "SuperH Mobile LCDC framebuffer support" depends on FB && (SUPERH || ARCH_SHMOBILE) && HAVE_CLK depends on FB_SH_MOBILE_MERAM || !FB_SH_MOBILE_MERAM + depends on BACKLIGHT_CLASS_DEVICE select FB_SYS_FILLRECT select FB_SYS_COPYAREA select FB_SYS_IMAGEBLIT select FB_SYS_FOPS select FB_DEFERRED_IO - select FB_BACKLIGHT select SH_MIPI_DSI if SH_LCD_MIPI_DSI ---help--- Frame buffer driver for the on-chip SH-Mobile LCD controller. @@ -2356,10 +2349,10 @@ config FB_MSM config FB_MX3 tristate "MX3 Framebuffer support" depends on FB && MX3_IPU + depends on BACKLIGHT_CLASS_DEVICE select FB_CFB_FILLRECT select FB_CFB_COPYAREA select FB_CFB_IMAGEBLIT - select BACKLIGHT_CLASS_DEVICE default y help This is a framebuffer device for the i.MX31 LCD Controller. So diff --git a/drivers/video/fbdev/core/fbsysfs.c b/drivers/video/fbdev/core/fbsysfs.c index 53444ac19fe0..8f766f14038e 100644 --- a/drivers/video/fbdev/core/fbsysfs.c +++ b/drivers/video/fbdev/core/fbsysfs.c @@ -59,7 +59,7 @@ struct fb_info *framebuffer_alloc(size_t size, struct device *dev)
info->device = dev;
-#ifdef CONFIG_FB_BACKLIGHT +#if IS_ENABLED(CONFIG_BACKLIGHT_CLASS_DEVICE) mutex_init(&info->bl_curve_mutex); #endif
@@ -428,7 +428,7 @@ static ssize_t show_fbstate(struct device *device, return snprintf(buf, PAGE_SIZE, "%d\n", fb_info->state); }
-#ifdef CONFIG_FB_BACKLIGHT +#if IS_ENABLED(CONFIG_BACKLIGHT_CLASS_DEVICE) static ssize_t store_bl_curve(struct device *device, struct device_attribute *attr, const char *buf, size_t count) @@ -517,7 +517,7 @@ static struct device_attribute device_attrs[] = { __ATTR(stride, S_IRUGO, show_stride, NULL), __ATTR(rotate, S_IRUGO|S_IWUSR, show_rotate, store_rotate), __ATTR(state, S_IRUGO|S_IWUSR, show_fbstate, store_fbstate), -#ifdef CONFIG_FB_BACKLIGHT +#if IS_ENABLED(CONFIG_BACKLIGHT_CLASS_DEVICE) __ATTR(bl_curve, S_IRUGO|S_IWUSR, show_bl_curve, store_bl_curve), #endif }; @@ -558,7 +558,7 @@ void fb_cleanup_device(struct fb_info *fb_info) } }
-#ifdef CONFIG_FB_BACKLIGHT +#if IS_ENABLED(CONFIG_BACKLIGHT_CLASS_DEVICE) /* This function generates a linear backlight curve * * 0: off diff --git a/include/linux/fb.h b/include/linux/fb.h index 09bb7a18d287..47e7742fdc9e 100644 --- a/include/linux/fb.h +++ b/include/linux/fb.h @@ -461,7 +461,7 @@ struct fb_info { struct list_head modelist; /* mode list */ struct fb_videomode *mode; /* current mode */
-#ifdef CONFIG_FB_BACKLIGHT +#if IS_ENABLED(CONFIG_BACKLIGHT_CLASS_DEVICE) /* assigned backlight device */ /* set before framebuffer registration, remove after unregister */ diff --git a/include/uapi/linux/fb.h b/include/uapi/linux/fb.h index fb795c3b3c17..a7a4be063432 100644 --- a/include/uapi/linux/fb.h +++ b/include/uapi/linux/fb.h @@ -392,7 +392,7 @@ struct fb_cursor { struct fb_image image; /* Cursor image */ };
-#ifdef CONFIG_FB_BACKLIGHT +#if IS_ENABLED(CONFIG_BACKLIGHT_CLASS_DEVICE) /* Settings for the generic backlight code */ #define FB_BACKLIGHT_LEVELS 128 #define FB_BACKLIGHT_MAX 0xFF
On Sat, Oct 18, 2014 at 12:13:23AM +0300, Jani Nikula wrote:
Documentation/kbuild/kconfig-language.txt warns to use select with care, and in general use select only for non-visible symbols and for symbols with no dependencies, because select will force a symbol to a value without visiting the dependencies.
Select has become particularly problematic, interdependently, with the BACKLIGHT_CLASS_DEVICE and ACPI_VIDEO configs. For example:
scripts/kconfig/conf --randconfig Kconfig KCONFIG_SEED=0x48312B00 warning: (DRM_RADEON && DRM_NOUVEAU && DRM_I915 && DRM_GMA500 && DRM_SHMOBILE && DRM_TILCDC && FB_BACKLIGHT && FB_MX3 && USB_APPLEDISPLAY && FB_OLPC_DCON && ASUS_LAPTOP && SONY_LAPTOP && THINKPAD_ACPI && EEEPC_LAPTOP && ACPI_CMPC && SAMSUNG_Q10) selects BACKLIGHT_CLASS_DEVICE which has unmet direct dependencies (HAS_IOMEM && BACKLIGHT_LCD_SUPPORT) warning: (DRM_RADEON && DRM_NOUVEAU && DRM_I915 && DRM_GMA500 && DRM_SHMOBILE && DRM_TILCDC && FB_BACKLIGHT && FB_MX3 && USB_APPLEDISPLAY && FB_OLPC_DCON && ASUS_LAPTOP && SONY_LAPTOP && THINKPAD_ACPI && EEEPC_LAPTOP && ACPI_CMPC && SAMSUNG_Q10) selects BACKLIGHT_CLASS_DEVICE which has unmet direct dependencies (HAS_IOMEM && BACKLIGHT_LCD_SUPPORT)
With tristates it's possible to end up selecting FOO=y depending on BAR=m in the config, which gets discovered at build time, not config time, like reported in the thread referenced below.
Do the following to fix the dependencies:
Depend on instead of select BACKLIGHT_CLASS_DEVICE everywhere. Drop select BACKLIGHT_LCD_SUPPORT in such cases, as it's a dependency of BACKLIGHT_CLASS_DEVICE.
Remove config FB_BACKLIGHT altogether, and replace it with a dependency on BACKLIGHT_CLASS_DEVICE. All configs selecting FB_BACKLIGHT select or depend on FB anyway, so we can simplify.
Depend on (ACPI && ACPI_VIDEO) || ACPI=n in several places instead of selecting ACPI_VIDEO and a number of its dependencies if ACPI is enabled. This is tied to backlight, as ACPI_VIDEO depends on BACKLIGHT_CLASS_DEVICE.
Replace a couple of select INPUT/VT with depends as it seemed to be necessary.
Reference: http://lkml.kernel.org/r/CA+r1ZhhmT4DrWtf6MbRQo5EqXwx+LxCqh15Vsu_d9WpftLhnxw... Reported-by: Jim Davis jim.epost@gmail.com Cc: Randy Dunlap rdunlap@infradead.org Cc: David Airlie airlied@linux.ie Cc: Daniel Vetter daniel.vetter@intel.com Cc: Greg Kroah-Hartman gregkh@linuxfoundation.org Cc: Darren Hart dvhart@infradead.org Cc: Laurent Pinchart laurent.pinchart@ideasonboard.com Cc: Benjamin Herrenschmidt benh@kernel.crashing.org Cc: Jens Frederich jfrederich@gmail.com Cc: Daniel Drake dsd@laptop.org Cc: Jon Nettleton jon.nettleton@gmail.com Cc: Jean-Christophe Plagniol-Villard plagnioj@jcrosoft.com Cc: Tomi Valkeinen tomi.valkeinen@ti.com Signed-off-by: Jani Nikula jani.nikula@intel.com
As for the drivers/platform/x86/Kconfig:
Acked-by: Darren Hart dvhart@linux.intel.com
Thanks,
On 18/10/14 00:13, Jani Nikula wrote:
Documentation/kbuild/kconfig-language.txt warns to use select with care, and in general use select only for non-visible symbols and for symbols with no dependencies, because select will force a symbol to a value without visiting the dependencies.
Select has become particularly problematic, interdependently, with the BACKLIGHT_CLASS_DEVICE and ACPI_VIDEO configs. For example:
scripts/kconfig/conf --randconfig Kconfig KCONFIG_SEED=0x48312B00 warning: (DRM_RADEON && DRM_NOUVEAU && DRM_I915 && DRM_GMA500 && DRM_SHMOBILE && DRM_TILCDC && FB_BACKLIGHT && FB_MX3 && USB_APPLEDISPLAY && FB_OLPC_DCON && ASUS_LAPTOP && SONY_LAPTOP && THINKPAD_ACPI && EEEPC_LAPTOP && ACPI_CMPC && SAMSUNG_Q10) selects BACKLIGHT_CLASS_DEVICE which has unmet direct dependencies (HAS_IOMEM && BACKLIGHT_LCD_SUPPORT) warning: (DRM_RADEON && DRM_NOUVEAU && DRM_I915 && DRM_GMA500 && DRM_SHMOBILE && DRM_TILCDC && FB_BACKLIGHT && FB_MX3 && USB_APPLEDISPLAY && FB_OLPC_DCON && ASUS_LAPTOP && SONY_LAPTOP && THINKPAD_ACPI && EEEPC_LAPTOP && ACPI_CMPC && SAMSUNG_Q10) selects BACKLIGHT_CLASS_DEVICE which has unmet direct dependencies (HAS_IOMEM && BACKLIGHT_LCD_SUPPORT)
With tristates it's possible to end up selecting FOO=y depending on BAR=m in the config, which gets discovered at build time, not config time, like reported in the thread referenced below.
Do the following to fix the dependencies:
Depend on instead of select BACKLIGHT_CLASS_DEVICE everywhere. Drop select BACKLIGHT_LCD_SUPPORT in such cases, as it's a dependency of BACKLIGHT_CLASS_DEVICE.
Remove config FB_BACKLIGHT altogether, and replace it with a dependency on BACKLIGHT_CLASS_DEVICE. All configs selecting FB_BACKLIGHT select or depend on FB anyway, so we can simplify.
Depend on (ACPI && ACPI_VIDEO) || ACPI=n in several places instead of selecting ACPI_VIDEO and a number of its dependencies if ACPI is enabled. This is tied to backlight, as ACPI_VIDEO depends on BACKLIGHT_CLASS_DEVICE.
Replace a couple of select INPUT/VT with depends as it seemed to be necessary.
While doing 'depends on' instead of 'select' is an "easy" fix for this, I do dislike it quite a bit. It's a major pain to go around the kernel config, trying to find all the dependencies that a particular driver wants. If I need fb-foobar, I should just be able to enable it, instead of first searching and selecting its minor dependencies individually.
So, not a NACK, but a "isn't there an another way to fix this?".
Looking at backlight... BACKLIGHT_LCD_SUPPORT seems to be a "meta" option, it only enables a Kconfig submenu.
So I think we could just remove the whole BACKLIGHT_LCD_SUPPORT option. But if we do that, all the items in drivers/video/backlight/Kconfig with default 'y' or 'm' would get enabled by default, so I think we should remove the 'default's from that file. That makes sense in any case, as I don't see why "HP Jornada 700 series LCD Driver" should be "default y".
BACKLIGHT_CLASS_DEVICE doesn't depend on anything except BACKLIGHT_LCD_SUPPORT, so after removing BACKLIGHT_LCD_SUPPORT it should be safe to 'select' BACKLIGHT_CLASS_DEVICE.
BACKLIGHT_CLASS_DEVICE could be made a hidden option, and the drivers in drivers/video/backlight/Kconfig which are under BACKLIGHT_CLASS_DEVICE could be made to select BACKLIGHT_CLASS_DEVICE instead.
That doesn't exactly fix anything, but I think it makes sense as BACKLIGHT_CLASS_DEVICE is something that's selected from all around the kernel, so it should be a selectable "library" instead of a Kconfig menu option.
I didn't look at the ACPI_VIDEO side, so no idea how messy that is.
Tomi
On Wed, Oct 22, 2014 at 11:02:26AM +0300, Tomi Valkeinen wrote:
On 18/10/14 00:13, Jani Nikula wrote:
Documentation/kbuild/kconfig-language.txt warns to use select with care, and in general use select only for non-visible symbols and for symbols with no dependencies, because select will force a symbol to a value without visiting the dependencies.
Select has become particularly problematic, interdependently, with the BACKLIGHT_CLASS_DEVICE and ACPI_VIDEO configs. For example:
scripts/kconfig/conf --randconfig Kconfig KCONFIG_SEED=0x48312B00 warning: (DRM_RADEON && DRM_NOUVEAU && DRM_I915 && DRM_GMA500 && DRM_SHMOBILE && DRM_TILCDC && FB_BACKLIGHT && FB_MX3 && USB_APPLEDISPLAY && FB_OLPC_DCON && ASUS_LAPTOP && SONY_LAPTOP && THINKPAD_ACPI && EEEPC_LAPTOP && ACPI_CMPC && SAMSUNG_Q10) selects BACKLIGHT_CLASS_DEVICE which has unmet direct dependencies (HAS_IOMEM && BACKLIGHT_LCD_SUPPORT) warning: (DRM_RADEON && DRM_NOUVEAU && DRM_I915 && DRM_GMA500 && DRM_SHMOBILE && DRM_TILCDC && FB_BACKLIGHT && FB_MX3 && USB_APPLEDISPLAY && FB_OLPC_DCON && ASUS_LAPTOP && SONY_LAPTOP && THINKPAD_ACPI && EEEPC_LAPTOP && ACPI_CMPC && SAMSUNG_Q10) selects BACKLIGHT_CLASS_DEVICE which has unmet direct dependencies (HAS_IOMEM && BACKLIGHT_LCD_SUPPORT)
With tristates it's possible to end up selecting FOO=y depending on BAR=m in the config, which gets discovered at build time, not config time, like reported in the thread referenced below.
Do the following to fix the dependencies:
Depend on instead of select BACKLIGHT_CLASS_DEVICE everywhere. Drop select BACKLIGHT_LCD_SUPPORT in such cases, as it's a dependency of BACKLIGHT_CLASS_DEVICE.
Remove config FB_BACKLIGHT altogether, and replace it with a dependency on BACKLIGHT_CLASS_DEVICE. All configs selecting FB_BACKLIGHT select or depend on FB anyway, so we can simplify.
Depend on (ACPI && ACPI_VIDEO) || ACPI=n in several places instead of selecting ACPI_VIDEO and a number of its dependencies if ACPI is enabled. This is tied to backlight, as ACPI_VIDEO depends on BACKLIGHT_CLASS_DEVICE.
Replace a couple of select INPUT/VT with depends as it seemed to be necessary.
While doing 'depends on' instead of 'select' is an "easy" fix for this, I do dislike it quite a bit. It's a major pain to go around the kernel config, trying to find all the dependencies that a particular driver wants. If I need fb-foobar, I should just be able to enable it, instead of first searching and selecting its minor dependencies individually.
So, not a NACK, but a "isn't there an another way to fix this?".
Looking at backlight... BACKLIGHT_LCD_SUPPORT seems to be a "meta" option, it only enables a Kconfig submenu.
So I think we could just remove the whole BACKLIGHT_LCD_SUPPORT option. But if we do that, all the items in drivers/video/backlight/Kconfig with default 'y' or 'm' would get enabled by default, so I think we should remove the 'default's from that file. That makes sense in any case, as I don't see why "HP Jornada 700 series LCD Driver" should be "default y".
BACKLIGHT_CLASS_DEVICE doesn't depend on anything except BACKLIGHT_LCD_SUPPORT, so after removing BACKLIGHT_LCD_SUPPORT it should be safe to 'select' BACKLIGHT_CLASS_DEVICE.
BACKLIGHT_CLASS_DEVICE could be made a hidden option, and the drivers in drivers/video/backlight/Kconfig which are under BACKLIGHT_CLASS_DEVICE could be made to select BACKLIGHT_CLASS_DEVICE instead.
That doesn't exactly fix anything, but I think it makes sense as BACKLIGHT_CLASS_DEVICE is something that's selected from all around the kernel, so it should be a selectable "library" instead of a Kconfig menu option.
I didn't look at the ACPI_VIDEO side, so no idea how messy that is.
If we want to make BACKLIGHT_CLASS_DEVICE into a library thing then I guess we could do that, but we must then also drag it out of all the other meta options to make sure it's always available. No need I think to ditch the entire BACKLIGHT_LCD_SUPPORT meta option. And then everyone could select it.
The problem is if you mix depends and select Kconfig falls over and starts to see loops where there are none. So you really can't ever mix them for the same symbol.
I think if we get the BACKLIGHT_CLASS_DEVICE out of the picture with that ACPI_VIDEO should be fixable with some
select ACPI_VIDEO if ACPI
or so. Currently that doesn't work because of the backlight class knob and select being broken. -Daniel
On 23/10/14 11:10, Daniel Vetter wrote:
If we want to make BACKLIGHT_CLASS_DEVICE into a library thing then I guess we could do that, but we must then also drag it out of all the other meta options to make sure it's always available. No need I think to ditch
BACKLIGHT_CLASS_DEVICE only depends on HAS_IOMEM and BACKLIGHT_LCD_SUPPORT so there are no other meta options to avoid. HAS_IOMEM comes from drivers/video/Kconfig's "Graphics support", and I guess we can ignore it.
the entire BACKLIGHT_LCD_SUPPORT meta option. And then everyone could select it.
I don't quite understand what purpose does BACKLIGHT_LCD_SUPPORT serve. It doesn't enable any code, it just opens up new Kconfig options. Why can't the Kconfig options be always available? It's just another option to 'select', without any reason I can see.
Tomi
On Wed, 22 Oct 2014, Tomi Valkeinen tomi.valkeinen@ti.com wrote:
On 18/10/14 00:13, Jani Nikula wrote:
Documentation/kbuild/kconfig-language.txt warns to use select with care, and in general use select only for non-visible symbols and for symbols with no dependencies, because select will force a symbol to a value without visiting the dependencies.
Select has become particularly problematic, interdependently, with the BACKLIGHT_CLASS_DEVICE and ACPI_VIDEO configs. For example:
scripts/kconfig/conf --randconfig Kconfig KCONFIG_SEED=0x48312B00 warning: (DRM_RADEON && DRM_NOUVEAU && DRM_I915 && DRM_GMA500 && DRM_SHMOBILE && DRM_TILCDC && FB_BACKLIGHT && FB_MX3 && USB_APPLEDISPLAY && FB_OLPC_DCON && ASUS_LAPTOP && SONY_LAPTOP && THINKPAD_ACPI && EEEPC_LAPTOP && ACPI_CMPC && SAMSUNG_Q10) selects BACKLIGHT_CLASS_DEVICE which has unmet direct dependencies (HAS_IOMEM && BACKLIGHT_LCD_SUPPORT) warning: (DRM_RADEON && DRM_NOUVEAU && DRM_I915 && DRM_GMA500 && DRM_SHMOBILE && DRM_TILCDC && FB_BACKLIGHT && FB_MX3 && USB_APPLEDISPLAY && FB_OLPC_DCON && ASUS_LAPTOP && SONY_LAPTOP && THINKPAD_ACPI && EEEPC_LAPTOP && ACPI_CMPC && SAMSUNG_Q10) selects BACKLIGHT_CLASS_DEVICE which has unmet direct dependencies (HAS_IOMEM && BACKLIGHT_LCD_SUPPORT)
With tristates it's possible to end up selecting FOO=y depending on BAR=m in the config, which gets discovered at build time, not config time, like reported in the thread referenced below.
Do the following to fix the dependencies:
Depend on instead of select BACKLIGHT_CLASS_DEVICE everywhere. Drop select BACKLIGHT_LCD_SUPPORT in such cases, as it's a dependency of BACKLIGHT_CLASS_DEVICE.
Remove config FB_BACKLIGHT altogether, and replace it with a dependency on BACKLIGHT_CLASS_DEVICE. All configs selecting FB_BACKLIGHT select or depend on FB anyway, so we can simplify.
Depend on (ACPI && ACPI_VIDEO) || ACPI=n in several places instead of selecting ACPI_VIDEO and a number of its dependencies if ACPI is enabled. This is tied to backlight, as ACPI_VIDEO depends on BACKLIGHT_CLASS_DEVICE.
Replace a couple of select INPUT/VT with depends as it seemed to be necessary.
While doing 'depends on' instead of 'select' is an "easy" fix for this, I do dislike it quite a bit. It's a major pain to go around the kernel config, trying to find all the dependencies that a particular driver wants. If I need fb-foobar, I should just be able to enable it, instead of first searching and selecting its minor dependencies individually.
Agreed, but I don't think that's specific to this patch.
So, not a NACK, but a "isn't there an another way to fix this?".
I think the real answer would be to fix kconfig to also show menu items whose dependencies are not met, and then recursively enabling the dependencies when the item is enabled. Beyond my scope.
Looking at backlight... BACKLIGHT_LCD_SUPPORT seems to be a "meta" option, it only enables a Kconfig submenu.
So I think we could just remove the whole BACKLIGHT_LCD_SUPPORT option. But if we do that, all the items in drivers/video/backlight/Kconfig with default 'y' or 'm' would get enabled by default, so I think we should remove the 'default's from that file. That makes sense in any case, as I don't see why "HP Jornada 700 series LCD Driver" should be "default y".
BACKLIGHT_CLASS_DEVICE doesn't depend on anything except BACKLIGHT_LCD_SUPPORT, so after removing BACKLIGHT_LCD_SUPPORT it should be safe to 'select' BACKLIGHT_CLASS_DEVICE.
BACKLIGHT_CLASS_DEVICE could be made a hidden option, and the drivers in drivers/video/backlight/Kconfig which are under BACKLIGHT_CLASS_DEVICE could be made to select BACKLIGHT_CLASS_DEVICE instead.
I think it should be possible to choose between y and m when it's selected, and it should be possible to enable it when it's not selected by any drivers. I'm not sure a hidden option is good for that.
That doesn't exactly fix anything, but I think it makes sense as BACKLIGHT_CLASS_DEVICE is something that's selected from all around the kernel, so it should be a selectable "library" instead of a Kconfig menu option.
At least for drm/i915 BACKLIGHT_CLASS_DEVICE is "an option". We use it if it's enabled, but we are just fine if it's not. I've learned the way to express that is
depends on BACKLIGHT_CLASS_DEVICE || BACKLIGHT_CLASS_DEVICE=n
but I don't think there's a way to express that in terms of select, is there? The dependency above guarantees there's no DRM_I915=y and BACKLIGHT_CLASS_DEVICE=m combo which would fail. And this, btw, is where this whole patch got started, as select didn't handle that properly.
I didn't look at the ACPI_VIDEO side, so no idea how messy that is.
Basically it's another dependency on BACKLIGHT_CLASS_DEVICE. I can only imagine trying to solve this problem with select is going to end up in recursive dependencies that spread out and need changing about as wide as this patch.
In the end, I agree with the problem you have with this patch, but yet I think it's the right thing to do in terms of expressing the dependencies.
BR, Jani.
On 27/10/14 13:59, Jani Nikula wrote:
While doing 'depends on' instead of 'select' is an "easy" fix for this, I do dislike it quite a bit. It's a major pain to go around the kernel config, trying to find all the dependencies that a particular driver wants. If I need fb-foobar, I should just be able to enable it, instead of first searching and selecting its minor dependencies individually.
Agreed, but I don't think that's specific to this patch.
Well, no, the generic problem is not specific to this patch, but we can avoid the issue with proper use of 'select' (at least in some cases), which is specific to this patch.
So, not a NACK, but a "isn't there an another way to fix this?".
I think the real answer would be to fix kconfig to also show menu items whose dependencies are not met, and then recursively enabling the dependencies when the item is enabled. Beyond my scope.
Looking at backlight... BACKLIGHT_LCD_SUPPORT seems to be a "meta" option, it only enables a Kconfig submenu.
So I think we could just remove the whole BACKLIGHT_LCD_SUPPORT option. But if we do that, all the items in drivers/video/backlight/Kconfig with default 'y' or 'm' would get enabled by default, so I think we should remove the 'default's from that file. That makes sense in any case, as I don't see why "HP Jornada 700 series LCD Driver" should be "default y".
BACKLIGHT_CLASS_DEVICE doesn't depend on anything except BACKLIGHT_LCD_SUPPORT, so after removing BACKLIGHT_LCD_SUPPORT it should be safe to 'select' BACKLIGHT_CLASS_DEVICE.
BACKLIGHT_CLASS_DEVICE could be made a hidden option, and the drivers in drivers/video/backlight/Kconfig which are under BACKLIGHT_CLASS_DEVICE could be made to select BACKLIGHT_CLASS_DEVICE instead.
I think it should be possible to choose between y and m when it's
If I'm not mistaken, if CONFIG_FOO is 'm', and it 'select's CONFIG_BAR, and CONFIG_BAR is tristate, then CONFIG_BAR will be set to 'm'.
selected, and it should be possible to enable it when it's not selected by any drivers. I'm not sure a hidden option is good for that.
Why would you want to enable it if no one uses it? Does BACKLIGHT_CLASS_DEVICE enable something even if no driver uses it?
That doesn't exactly fix anything, but I think it makes sense as BACKLIGHT_CLASS_DEVICE is something that's selected from all around the kernel, so it should be a selectable "library" instead of a Kconfig menu option.
At least for drm/i915 BACKLIGHT_CLASS_DEVICE is "an option". We use it if it's enabled, but we are just fine if it's not. I've learned the way to express that is
depends on BACKLIGHT_CLASS_DEVICE || BACKLIGHT_CLASS_DEVICE=n
but I don't think there's a way to express that in terms of select, is there? The dependency above guarantees there's no DRM_I915=y and BACKLIGHT_CLASS_DEVICE=m combo which would fail. And this, btw, is where this whole patch got started, as select didn't handle that properly.
If backlight support is considered an option for drm/i915, then I think there should be a Kconfig option for i915 to enable backlight support, which in turn selects BACKLIGHT_CLASS_DEVICE. And that select will force BACKLIGHT_CLASS_DEVICE to be built-in if drm/i915 is built-in.
Oh, but it doesn't work optimally with modules. The new option needed for that would be boolean, so BACKLIGHT_CLASS_DEVICE would always be either y or n. Sigh...
I didn't look at the ACPI_VIDEO side, so no idea how messy that is.
Basically it's another dependency on BACKLIGHT_CLASS_DEVICE. I can only imagine trying to solve this problem with select is going to end up in recursive dependencies that spread out and need changing about as wide as this patch.
If ACPI_VIDEO uses select to enable BACKLIGHT_CLASS_DEVICE, then, I think, selecting ACPI_VIDEO will also select BACKLIGHT_CLASS_DEVICE. So I don't right away see any recursive dependencies. Or what did you have in mind?
In the end, I agree with the problem you have with this patch, but yet I think it's the right thing to do in terms of expressing the dependencies.
Well, dri/i915 doesn't exactly depend on backlight, if I understood you correctly. Instead, backlight is an option for dri/i915, and you kind of hack it to be implemented with that 'depends on BACKLIGHT_CLASS_DEVICE || BACKLIGHT_CLASS_DEVICE=n'.
I guess it's debatable whether drivers should automatically use features in the kernel if they happen to be enabled in the Kconfig, or should they be individually enabled for that driver. I personally like the latter option, as it allows more precise control, but it probably also depends on the feature in question.
I also think the 'depends on BACKLIGHT_CLASS_DEVICE || BACKLIGHT_CLASS_DEVICE=n' pattern is quite... interesting (i.e. sounds like a hack to me =).
Tomi
On 10/27/14 06:13, Tomi Valkeinen wrote:
On 27/10/14 13:59, Jani Nikula wrote:
While doing 'depends on' instead of 'select' is an "easy" fix for this, I do dislike it quite a bit. It's a major pain to go around the kernel config, trying to find all the dependencies that a particular driver wants. If I need fb-foobar, I should just be able to enable it, instead of first searching and selecting its minor dependencies individually.
Agreed, but I don't think that's specific to this patch.
Well, no, the generic problem is not specific to this patch, but we can avoid the issue with proper use of 'select' (at least in some cases), which is specific to this patch.
So, not a NACK, but a "isn't there an another way to fix this?".
I think the real answer would be to fix kconfig to also show menu items whose dependencies are not met, and then recursively enabling the dependencies when the item is enabled. Beyond my scope.
Looking at backlight... BACKLIGHT_LCD_SUPPORT seems to be a "meta" option, it only enables a Kconfig submenu.
So I think we could just remove the whole BACKLIGHT_LCD_SUPPORT option. But if we do that, all the items in drivers/video/backlight/Kconfig with default 'y' or 'm' would get enabled by default, so I think we should remove the 'default's from that file. That makes sense in any case, as I don't see why "HP Jornada 700 series LCD Driver" should be "default y".
BACKLIGHT_CLASS_DEVICE doesn't depend on anything except BACKLIGHT_LCD_SUPPORT, so after removing BACKLIGHT_LCD_SUPPORT it should be safe to 'select' BACKLIGHT_CLASS_DEVICE.
BACKLIGHT_CLASS_DEVICE could be made a hidden option, and the drivers in drivers/video/backlight/Kconfig which are under BACKLIGHT_CLASS_DEVICE could be made to select BACKLIGHT_CLASS_DEVICE instead.
I think it should be possible to choose between y and m when it's
If I'm not mistaken, if CONFIG_FOO is 'm', and it 'select's CONFIG_BAR, and CONFIG_BAR is tristate, then CONFIG_BAR will be set to 'm'.
selected, and it should be possible to enable it when it's not selected by any drivers. I'm not sure a hidden option is good for that.
Why would you want to enable it if no one uses it? Does BACKLIGHT_CLASS_DEVICE enable something even if no driver uses it?
That doesn't exactly fix anything, but I think it makes sense as BACKLIGHT_CLASS_DEVICE is something that's selected from all around the kernel, so it should be a selectable "library" instead of a Kconfig menu option.
At least for drm/i915 BACKLIGHT_CLASS_DEVICE is "an option". We use it if it's enabled, but we are just fine if it's not. I've learned the way to express that is
depends on BACKLIGHT_CLASS_DEVICE || BACKLIGHT_CLASS_DEVICE=n
but I don't think there's a way to express that in terms of select, is there? The dependency above guarantees there's no DRM_I915=y and BACKLIGHT_CLASS_DEVICE=m combo which would fail. And this, btw, is where this whole patch got started, as select didn't handle that properly.
If backlight support is considered an option for drm/i915, then I think there should be a Kconfig option for i915 to enable backlight support, which in turn selects BACKLIGHT_CLASS_DEVICE. And that select will force BACKLIGHT_CLASS_DEVICE to be built-in if drm/i915 is built-in.
Oh, but it doesn't work optimally with modules. The new option needed for that would be boolean, so BACKLIGHT_CLASS_DEVICE would always be either y or n. Sigh...
I didn't look at the ACPI_VIDEO side, so no idea how messy that is.
Basically it's another dependency on BACKLIGHT_CLASS_DEVICE. I can only imagine trying to solve this problem with select is going to end up in recursive dependencies that spread out and need changing about as wide as this patch.
If ACPI_VIDEO uses select to enable BACKLIGHT_CLASS_DEVICE, then, I think, selecting ACPI_VIDEO will also select BACKLIGHT_CLASS_DEVICE. So I don't right away see any recursive dependencies. Or what did you have in mind?
In the end, I agree with the problem you have with this patch, but yet I think it's the right thing to do in terms of expressing the dependencies.
Well, dri/i915 doesn't exactly depend on backlight, if I understood you correctly. Instead, backlight is an option for dri/i915, and you kind of hack it to be implemented with that 'depends on BACKLIGHT_CLASS_DEVICE || BACKLIGHT_CLASS_DEVICE=n'.
I guess it's debatable whether drivers should automatically use features in the kernel if they happen to be enabled in the Kconfig, or should they be individually enabled for that driver. I personally like the latter option, as it allows more precise control, but it probably also depends on the feature in question.
I also think the 'depends on BACKLIGHT_CLASS_DEVICE || BACKLIGHT_CLASS_DEVICE=n' pattern is quite... interesting (i.e. sounds like a hack to me =).
It does exactly what is needed and it is used in many places in kernel Kconfig files.
On Tue, 2014-10-28 at 13:29 -0700, Randy Dunlap wrote:
On 10/27/14 06:13, Tomi Valkeinen wrote:
I also think the 'depends on BACKLIGHT_CLASS_DEVICE || BACKLIGHT_CLASS_DEVICE=n' pattern is quite... interesting (i.e. sounds like a hack to me =).
It does exactly what is needed and it is used in many places in kernel Kconfig files.
Is there any reason you can't do:
depends on BACKLIGHT_CLASS_DEVICE != m
cheers
On Wed, 29 Oct 2014, Michael Ellerman mpe@ellerman.id.au wrote:
On Tue, 2014-10-28 at 13:29 -0700, Randy Dunlap wrote:
On 10/27/14 06:13, Tomi Valkeinen wrote:
I also think the 'depends on BACKLIGHT_CLASS_DEVICE || BACKLIGHT_CLASS_DEVICE=n' pattern is quite... interesting (i.e. sounds like a hack to me =).
It does exactly what is needed and it is used in many places in kernel Kconfig files.
Is there any reason you can't do:
depends on BACKLIGHT_CLASS_DEVICE != m
That's not the same thing. The FOO || FOO=n allows for all options, but forbids it being a module when the option depending on it is built-in. Obviously something that's built-in can't depend on something built as a module.
BR, Jani.
On Wed, 2014-10-29 at 09:54 +0200, Jani Nikula wrote:
On Wed, 29 Oct 2014, Michael Ellerman mpe@ellerman.id.au wrote:
On Tue, 2014-10-28 at 13:29 -0700, Randy Dunlap wrote:
On 10/27/14 06:13, Tomi Valkeinen wrote:
I also think the 'depends on BACKLIGHT_CLASS_DEVICE || BACKLIGHT_CLASS_DEVICE=n' pattern is quite... interesting (i.e. sounds like a hack to me =).
It does exactly what is needed and it is used in many places in kernel Kconfig files.
Is there any reason you can't do:
depends on BACKLIGHT_CLASS_DEVICE != m
That's not the same thing. The FOO || FOO=n allows for all options, but forbids it being a module when the option depending on it is built-in.
OK right. Because "BAR depends on FOO" is short for "depends on FOO=y || FOO=m", but also adds the implicit condition that if FOO=m then BAR must also be m.
Thanks for clueing me in.
cheers
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