On Thu, 2010-04-01 at 09:19 +0800, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rjw@xxxxxxx>
>
> On Acer Ferrari One, when _BQC is invoked for the first time, the
> minimum brightness is returned, so the ACPI video drivers sets the
> minimum brightness on boot. This is not desirable, so use the
> following rule:
> If _BQC initially returns an invalid value or the minimum
> brightness, use either the brightness level supposed to be
> used on AC power, or the brightness level supposed to be
> used on battery, depending on whether or not the system is
> on AC power. If these values are not exported by the BIOS,
> use the maximum brightness level.
>
> Signed-off-by: Rafael J. Wysocki <rjw@xxxxxxx>
> ---
> drivers/acpi/video.c | 26 +++++++++++++++++++++++---
> 1 file changed, 23 insertions(+), 3 deletions(-)
>
> Index: linux-2.6/drivers/acpi/video.c
> ===================================================================
> --- linux-2.6.orig/drivers/acpi/video.c
> +++ linux-2.6/drivers/acpi/video.c
> @@ -44,6 +44,7 @@
> #include <acpi/acpi_bus.h>
> #include <acpi/acpi_drivers.h>
> #include <linux/suspend.h>
> +#include <linux/power_supply.h>
>
> #define PREFIX "ACPI: "
>
> @@ -920,11 +928,20 @@ acpi_video_init_brightness(struct acpi_v
> * Set the backlight to the initial state.
> * On some buggy laptops, _BQC returns an uninitialized value
> * when invoked for the first time, i.e. level_old is invalid.
> - * set the backlight to max_level in this case
> + * On some other systems _BQC returns the minimum brightness
> + * when invoked for the first time, which also usually is
> + * undesirable. In that cases use the "AC power" value if on AC
> + * power or the "battery" value otherwise. If these vaules are
> + * not exported, use max_level.
> */
> - for (i = 2; i < br->count; i++)
> - if (level_old == br->levels[i])
> + for (i = 3; i < br->count; i++)
> + if (level_old == br->levels[i]) {
> level = level_old;
> + goto set_level;
> + }
> + if (!br->flags._BCL_no_ac_battery_levels)
> + level = power_supply_is_system_supplied() ?
> +
> br->levels[0] : br->levels[1];
this doesn't work currently.
br->levels[0] and br->levels[1] doesn't equal the "AC power" value and
"Battery" value, because the "AC power" and "Battery" value is not
exported by many BIOS at all.
But we can make it work if we fake the AC and Battery value for these
laptops, which is not done yet. For example, set the AC power value the
maximum brightness level, if it's not exported by BIOS.
thanks,
rui
> goto set_level;
> }
>
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