Commit bd8ba205 authored by Hans de Goede's avatar Hans de Goede Committed by Rafael J. Wysocki

ACPI / video: Filter the _BCL table for duplicate brightness values

Some devices have duplicate entries in there brightness levels table, ie
on my Dell Latitude E6430 the table looks like this:

[    3.686060] acpi backlight index   0, val 80
[    3.686095] acpi backlight index   1, val 50
[    3.686122] acpi backlight index   2, val 5
[    3.686147] acpi backlight index   3, val 5
[    3.686172] acpi backlight index   4, val 5
[    3.686197] acpi backlight index   5, val 5
[    3.686223] acpi backlight index   6, val 5
[    3.686248] acpi backlight index   7, val 5
[    3.686273] acpi backlight index   8, val 6
[    3.686332] acpi backlight index   9, val 7
[    3.686356] acpi backlight index  10, val 8
[    3.686380] acpi backlight index  11, val 9
etc.

Notice that brightness values 0-5 are all mapped to 5. This means that
if userspace writes any value between 0 and 5 to the brightness sysfs attribute
and then reads it, it will always return 0, which is somewhat unexpected.

This is a problem for ie gnome-settings-daemon, which uses read-modify-write
logic when the users presses the brightness up or down keys. This is done
this way to take brightness changes from other sources into account.

On this specific laptop what happens once the brightness has been set to 0,
is that gsd reads 0, adds 5, writes 5, and on the next brightness up key press
again reads 0, so things get stuck at the lowest brightness setting.

Filtering out the duplicate table entries, makes any write to brightness
read back as the written value as one would expect, fixing this.
Signed-off-by: default avatarHans de Goede <hdegoede@redhat.com>
Reviewed-by: default avatarAaron Lu <aaron.lu@intel.com>
Cc: All applicable <stable@vger.kernel.org>
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent 6d0abeca
...@@ -685,6 +685,7 @@ acpi_video_init_brightness(struct acpi_video_device *device) ...@@ -685,6 +685,7 @@ acpi_video_init_brightness(struct acpi_video_device *device)
union acpi_object *o; union acpi_object *o;
struct acpi_video_device_brightness *br = NULL; struct acpi_video_device_brightness *br = NULL;
int result = -EINVAL; int result = -EINVAL;
u32 value;
if (!ACPI_SUCCESS(acpi_video_device_lcd_query_levels(device, &obj))) { if (!ACPI_SUCCESS(acpi_video_device_lcd_query_levels(device, &obj))) {
ACPI_DEBUG_PRINT((ACPI_DB_INFO, "Could not query available " ACPI_DEBUG_PRINT((ACPI_DB_INFO, "Could not query available "
...@@ -715,7 +716,12 @@ acpi_video_init_brightness(struct acpi_video_device *device) ...@@ -715,7 +716,12 @@ acpi_video_init_brightness(struct acpi_video_device *device)
printk(KERN_ERR PREFIX "Invalid data\n"); printk(KERN_ERR PREFIX "Invalid data\n");
continue; continue;
} }
br->levels[count] = (u32) o->integer.value; value = (u32) o->integer.value;
/* Skip duplicate entries */
if (count > 2 && br->levels[count - 1] == value)
continue;
br->levels[count] = value;
if (br->levels[count] > max_level) if (br->levels[count] > max_level)
max_level = br->levels[count]; max_level = br->levels[count];
......
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