asle_set_backlight() needs to accept backlight request only if the
firmware controls the backlight. It used the following expression for
this purpose:
acpi_video_get_backlight_type() == acpi_backlight_native
This expression works well in practice, but has two semantic problems.
One is that it actually determines if a backlight device which directly
modifies hardware registers ("native backlight") exists. It is possible
that a device which does not have backlight at all incorrectly triggers
asle_set_backlight(), and the expression does not cover such a case.
Another problem is that acpi_video_get_backlight_type() always return
acpi_backlight_vendor in reality if CONFIG_ACPI_VIDEO is unset. It
means even its ability to determine the existence of native backlight is
somewhat limited.
This change introduces a new function backlight_device_non_raw_exists(),
which returns if the firmware is controlling the backlight, and is
always available if backlight support is enabled.
Signed-off-by: Akihiko Odaki <akihiko.odaki@xxxxxxxxxx>
---
drivers/gpu/drm/i915/display/intel_opregion.c | 3 ++-
drivers/video/backlight/backlight.c | 18 ++++++++++++++++++
include/linux/backlight.h | 1 +
3 files changed, 21 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/i915/display/intel_opregion.c b/drivers/gpu/drm/i915/display/intel_opregion.c
index caa07ef34f21..82ea02ab94c2 100644
--- a/drivers/gpu/drm/i915/display/intel_opregion.c
+++ b/drivers/gpu/drm/i915/display/intel_opregion.c
@@ -26,6 +26,7 @@
*/
#include <linux/acpi.h>
+#include <linux/backlight.h>
#include <linux/dmi.h>
#include <linux/firmware.h>
#include <acpi/video.h>
@@ -467,7 +468,7 @@ static u32 asle_set_backlight(struct drm_i915_private *dev_priv, u32 bclp)
drm_dbg(&dev_priv->drm, "bclp = 0x%08x\n", bclp);
- if (acpi_video_get_backlight_type() == acpi_backlight_native) {
+ if (!backlight_device_non_raw_exists()) {
drm_dbg_kms(&dev_priv->drm,
"opregion backlight request ignored\n");
return 0;
diff --git a/drivers/video/backlight/backlight.c b/drivers/video/backlight/backlight.c
index b788ff3d0f45..4f0ce463e250 100644
--- a/drivers/video/backlight/backlight.c
+++ b/drivers/video/backlight/backlight.c
@@ -516,6 +516,24 @@ struct backlight_device *backlight_device_get_by_name(const char *name)
}
EXPORT_SYMBOL(backlight_device_get_by_name);
+bool backlight_device_non_raw_exists(void)
+{
+ bool found = false;
+ struct backlight_device *bd;
+
+ mutex_lock(&backlight_dev_list_mutex);
+ list_for_each_entry(bd, &backlight_dev_list, entry) {
+ if (bd->props.type != BACKLIGHT_RAW) {
+ found = true;
+ break;
+ }
+ }
+ mutex_unlock(&backlight_dev_list_mutex);
+
+ return found;
+}
+EXPORT_SYMBOL(backlight_device_non_raw_exists);
+
/* deprecated - use devm_backlight_device_unregister() */
void backlight_device_unregister(struct backlight_device *bd)
{
diff --git a/include/linux/backlight.h b/include/linux/backlight.h
index 614653e07e3a..364ef6f99a9e 100644
--- a/include/linux/backlight.h
+++ b/include/linux/backlight.h
@@ -444,6 +444,7 @@ int backlight_register_notifier(struct notifier_block *nb);
int backlight_unregister_notifier(struct notifier_block *nb);
struct backlight_device *backlight_device_get_by_name(const char *name);
struct backlight_device *backlight_device_get_by_type(enum backlight_type type);
+bool backlight_device_non_raw_exists(void);
int backlight_device_set_brightness(struct backlight_device *bd,
unsigned long brightness);
--
2.37.3
