Currently we decide if the _BQC is using index by first setting the level to maximum, and then check if _BQC returned maximum; if not, we say it is using index. This is not true for some buggy systems, where the _BQC method will always return a constant value(e.g. 0 or 100 for the two broken system) and thus break the current logic. So this patch tries to enhance the quirk detect logic for _BQC: we do this by picking a test_level, it can be the maximum level or the mininum one based on some condition. And we don't make the assumption that if _BQC returned a value that is not what we just set, it must be using an index. Instead, we will compare the value returned from _BQC and if it doesn't match, see if the returned value is an index. And if still no, clear the capability of _BQC. Buglink: https://bugzilla.kernel.org/show_bug.cgi?id=42861 Buglink: https://bugzilla.kernel.org/show_bug.cgi?id=56011 Reported-and-tested-by: Artem Savkov <artem.savkov@xxxxxxxxx> Reported-by: Luis Medinas <lmedinas@xxxxxxxxx> Reported-by: Cheppes <cheppes@xxxxxxxxxxxxxx> Signed-off-by: Aaron Lu <aaron.lu@xxxxxxxxx> --- Thanks Cheppes <cheppes@xxxxxxxxxxxxxx> for the suggestion of choosing different levels to test, and also for the help of in code comment correction. drivers/acpi/video.c | 67 ++++++++++++++++++++++++++++++++++++++++++++-------- 1 file changed, 57 insertions(+), 10 deletions(-) diff --git a/drivers/acpi/video.c b/drivers/acpi/video.c index 3cdd047..306ea2a 100644 --- a/drivers/acpi/video.c +++ b/drivers/acpi/video.c @@ -632,6 +632,56 @@ acpi_video_cmp_level(const void *a, const void *b) } /* + * Decides if _BQC/_BCQ for this system is usable + * + * We do this by changing the level first and then read out the current + * brightness level, if the value does not match, find out if it is using + * index. If not, clear the _BQC/_BCQ capability. + */ +static int acpi_video_bqc_quirk(struct acpi_video_device *device, + int max_level, int current_level) +{ + struct acpi_video_device_brightness *br = device->brightness; + int result; + unsigned long long level; + int test_level; + + /* don't mess with existing known broken systems */ + if (bqc_offset_aml_bug_workaround) + return 0; + + /* + * Some systems always report current brightness level as maximum + * through _BQC, we need to test another value for them. + */ + test_level = current_level == max_level ? br->levels[2] : max_level; + + result = acpi_video_device_lcd_set_level(device, test_level); + if (result) + return result; + + result = acpi_video_device_lcd_get_level_current(device, &level, true); + if (result) + return result; + + if (level != test_level) { + /* buggy _BQC found, need to find out if it uses index */ + if (level < br->count) { + if (br->flags._BCL_reversed) + level = br->count - 3 - level; + if (br->levels[level + 2] == test_level) + br->flags._BQC_use_index = 1; + } + + if (!br->flags._BQC_use_index) + device->cap._BQC = device->cap._BCQ = 0; + } + + return 0; +} + + +/* * Arg: * device : video output device (LCD, CRT, ..) * @@ -742,18 +792,15 @@ acpi_video_init_brightness(struct acpi_video_device *device) if (result) goto out_free_levels; - /* - * Set the level to maximum and check if _BQC uses indexed value - */ - result = acpi_video_device_lcd_set_level(device, max_level); - if (result) - goto out_free_levels; - - result = acpi_video_device_lcd_get_level_current(device, &level, true); + result = acpi_video_bqc_quirk(device, max_level, level_old); if (result) goto out_free_levels; - - br->flags._BQC_use_index = (level == max_level ? 0 : 1); + /* + * cap._BQC may get cleared due to _BQC is found to be broken + * in acpi_video_bqc_quirk, so check again here. + */ + if (!device->cap._BQC) + goto set_level; if (use_bios_initial_backlight) { level = acpi_video_bqc_value_to_level(device, level_old); -- 1.8.1.4 -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
