From: David Herrmann <dh.herrmann at gmail.com>
So far backlights have only been controlled via sysfs. However, sysfs is not a proper user-space API for runtime modifications, and never was intended to provide such. The DRM drivers are now prepared to provide such a backlight link so user-space can control backlight via DRM connector properties. This allows us to employ the same access-management we use for mode-setting.
This patch adds few kernel-internal backlight helpers so we can modify backlights from within DRM.
Signed-off-by: David Herrmann <dh.herrmann at gmail.com> --- drivers/video/backlight/backlight.c | 65 +++++++++++++++++++++++++++++++++++++ include/linux/backlight.h | 16 +++++++++ 2 files changed, 81 insertions(+)
diff --git a/drivers/video/backlight/backlight.c b/drivers/video/backlight/backlight.c index 716c091..c7b335c 100644 --- a/drivers/video/backlight/backlight.c +++ b/drivers/video/backlight/backlight.c @@ -489,6 +489,71 @@ int backlight_unregister_notifier(struct notifier_block *nb) EXPORT_SYMBOL(backlight_unregister_notifier);
/** + * backlight_device_lookup - find a backlight device + * @name: sysname of the backlight device + * + * @return Reference to the backlight device, NULL if not found. + * + * This searches through all registered backlight devices for a device with the + * given device name. In case none is found, NULL is returned, otherwise a + * new reference to the backlight device is returned. You must drop this + * reference via backlight_device_unref() once done. + * Note that the devices might get unregistered at any time. You need to lock + * around this lookup and inside of your backlight-notifier if you need to know + * when a device gets unregistered. + * + * This function can be safely called from IRQ context. + */ +struct backlight_device *backlight_device_lookup(const char *name) +{ + struct backlight_device *bd; + unsigned long flags; + const char *t; + + spin_lock_irqsave(&backlight_dev_list_lock, flags); + + list_for_each_entry(bd, &backlight_dev_list, entry) { + t = dev_name(&bd->dev); + if (t && !strcmp(t, name)) + goto out; + } + + bd = NULL; + +out: + spin_unlock_irqrestore(&backlight_dev_list_lock, flags); + backlight_device_ref(bd); + return bd; +} +EXPORT_SYMBOL_GPL(backlight_device_lookup); + +/** + * backlight_set_brightness - set brightness on a backlight device + * @bd: backlight device to operate on + * @value: brightness value to set on the device + * @reason: backlight-change reason to use for notifications + * + * This is the in-kernel API equivalent of writing into the 'brightness' sysfs + * file. It calls into the underlying backlight driver to change the brightness + * value. The value is clamped according to device bounds. + * A uevent notification is sent with the reason set to @reason. + */ +void backlight_set_brightness(struct backlight_device *bd, unsigned int value, + enum backlight_update_reason reason) +{ + mutex_lock(&bd->ops_lock); + if (bd->ops) { + value = clamp(value, 0U, (unsigned)bd->props.max_brightness); + pr_debug("set brightness to %u\n", value); + bd->props.brightness = value; + backlight_update_status(bd); + } + mutex_unlock(&bd->ops_lock); + backlight_generate_event(bd, reason); +} +EXPORT_SYMBOL_GPL(backlight_set_brightness); + +/** * devm_backlight_device_register - resource managed backlight_device_register() * @dev: the device to register * @name: the name of the device diff --git a/include/linux/backlight.h b/include/linux/backlight.h index 5f2fd61..895c4661 100644 --- a/include/linux/backlight.h +++ b/include/linux/backlight.h @@ -146,6 +146,22 @@ extern int backlight_unregister_notifier(struct notifier_block *nb); extern struct backlight_device *backlight_device_get_by_type(enum backlight_type type); extern int backlight_device_set_brightness(struct backlight_device *bd, unsigned long brightness);
+struct backlight_device *backlight_device_lookup(const char *name); +void backlight_set_brightness(struct backlight_device *bd, unsigned int value, + enum backlight_update_reason reason); + +static inline void backlight_device_ref(struct backlight_device *bd) +{ + if (bd) + get_device(&bd->dev); +} + +static inline void backlight_device_unref(struct backlight_device *bd) +{ + if (bd) + put_device(&bd->dev); +} + #define to_backlight_device(obj) container_of(obj, struct backlight_device, dev)
static inline void * bl_get_data(struct backlight_device *bl_dev)