On Mon, 25 November 2013 Bjorn Helgaas wrote:
On Mon, Nov 25, 2013 at 12:54 PM, Bruno Prémont wrote:
On a MacBookAir2,1, booting to Linux with EFI though having no efifb built-in Xorg refuses to start with "no devices detected" because for the only VGA device available (NVidia Geforce 9400M) the sysfs attribute boot_vga is zero (instead of expected 1).
When CONFIG_FB_EFI is selected, efifb does provide its own vga_default_device() to report the PCI device matching global screen_info as determined during efifb setup.
Otherwise there is just a dummy or VGA_ARB's vga_default_device() that does not provide the right information.
Wouldn't it be cleaner to fix vga_default_device() so it returns the correct thing even when CONFIG_FB_EFI=n?
I would rather completely drop the vga_default_device() from efifb (CONFIG_FB_EFI) and just keep vga_default_device() for vga-arbitration/vga-switcheroo.
The fact that there are currently *two* instances of that function doesn't make life easy for determining who is providing it and when. drivers/gpu/vga/vgaarb.c:135 drivers/video/efifb.c:88 include/linux/vgaarb.h:190 (dummy)
On the other hand, boot_vga_show() falls back to poking PCI resources to flag a PCI device as boot_vga if vga_default_device() returned no PCI device (NULL).
To complement this PCI resource poking, this patch copies the validation code used to determine which PCI device to report as default VGA device by efifb into boot_vga_show().
If we do have to use logic like this, I'd like it better if it were factored into a single function called both here and from efifb_setup().
As of above, I would preferably drop that part of code from efifb_setup() and have the logic called only in one place and each time the same way. Otherwise efifb versus x86_sysfb+simplefb or directly going to native driver (nvoueau/radeon/...) behave differently without reason.
Bruno
Signed-off-by: Bruno Prémont bonbons@linux-vserver.org
Would it make sense to kill the corresponding code from efifb as it covers only a single case?
The other EFI capable system I have (AMD Ilano based, Gigabyte mainboard does report boot_vga=1, possibly through the resources poking and there Xorg starts properly without efifb built in.
Selecting CONFIG_X86_SYSFB (combined with CONFIG_FB_SIMPLE) does not help by itself, patching that one instead of PCI's boot_vga attribute directly would still not cover the case when neither of them is enabled.
drivers/pci/pci-sysfs.c | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+)
diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c index 7128cfd..91cac71 100644 --- a/drivers/pci/pci-sysfs.c +++ b/drivers/pci/pci-sysfs.c @@ -28,6 +28,7 @@ #include <linux/pci-aspm.h> #include <linux/slab.h> #include <linux/vgaarb.h> +#include <linux/screen_info.h> #include <linux/pm_runtime.h> #include "pci.h"
@@ -540,6 +541,26 @@ boot_vga_show(struct device *dev, struct device_attribute *attr, char *buf) if (vga_dev) return sprintf(buf, "%u\n", (pdev == vga_dev));
if ((pdev->class >> 8) == PCI_CLASS_DISPLAY_VGA) {resource_size_t start, end;int i;for (i = 0; i < DEVICE_COUNT_RESOURCE; i++) {if (!(pci_resource_flags(pdev, i) & IORESOURCE_MEM))continue;start = pci_resource_start(pdev, i);end = pci_resource_end(pdev, i);if (!start || !end)continue;if (screen_info.lfb_base >= start &&(screen_info.lfb_base + screen_info.lfb_size) < end)return sprintf(buf, "1\n");}}return sprintf(buf, "%u\n", !!(pdev->resource[PCI_ROM_RESOURCE].flags & IORESOURCE_ROM_SHADOW));