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Subject: Re: [PATCH v16 01/10] video: backlight: Add helpers to enable and
 disable backlight
To:     Daniel Thompson <daniel.thompson@linaro.org>,
        Meghana Madhyastha <meghana.madhyastha@gmail.com>,
        Lee Jones <lee.jones@linaro.org>,
        Jingoo Han <jingoohan1@gmail.com>,
        Thierry Reding <thierry.reding@gmail.com>,
        Tomi Valkeinen <tomi.valkeinen@ti.com>,
        Daniel Vetter <daniel.vetter@intel.com>,
        Sean Paul <seanpaul@chromium.org>,
        dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org
References: <cover.1516098341.git.meghana.madhyastha@gmail.com>
 <0ef2305477e69efdf61a378079fb7404a40c909f.1516098341.git.meghana.madhyastha@gmail.com>
 <84821d63-edc4-9a9a-db54-a180bf5fe9f6@linaro.org>
From:   =?UTF-8?Q?Noralf_Tr=c3=b8nnes?= <noralf@tronnes.org>
Message-ID: <7fe263d8-7b4a-68f1-2799-4b29d45dac89@tronnes.org>
Date:   Wed, 17 Jan 2018 23:03:24 +0100
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Den 17.01.2018 18.00, skrev Daniel Thompson:
>
>
> On 16/01/18 10:31, Meghana Madhyastha wrote:
>> Add helper functions backlight_enable and backlight_disable to
>> enable/disable a backlight device. These helper functions can
>> then be used by different drm and tinydrm drivers to avoid
>> repetition of code and also to enforce a uniform and consistent
>> way to enable/disable a backlight device.
>>
>> Signed-off-by: Meghana Madhyastha <meghana.madhyastha@gmail.com>
>
> To be clear I don't disagree with anthing Daniel V. said about the 
> horribly confused (and confusing) power states for backlight.
>
> Nevertheless I don't recall seeing any response (positive or negative) 
> to this post from v13:
> https://www.spinics.net/lists/dri-devel/msg154459.html
>

I see that Daniel V has answered while I was chasing this down, but anyways:

A grep suggests that omap1_bl is the only driver that only checks fb_blank.
All the other drivers check both fb_blank and power, a few check state. The
backlight fbdev notifier callback doesn't set power, but sets fb_blank and
state.

fb_blank was marked 'Due to be removed' 9 years ago, so it hasn't been
high priority.

So for completeness I guess it makes sense to set fb_blank.

Noralf.

$ grep -r -C10 "props\.fb_blank" .
./drivers/video/backlight/corgi_lcd.c-  if (bd->props.power != 
FB_BLANK_UNBLANK)
./drivers/video/backlight/corgi_lcd.c-          intensity = 0;
./drivers/video/backlight/corgi_lcd.c-
./drivers/video/backlight/corgi_lcd.c:  if (bd->props.fb_blank != 
FB_BLANK_UNBLANK)
./drivers/video/backlight/corgi_lcd.c-          intensity = 0;
--
./drivers/video/backlight/adp8860_bl.c- if (bl->props.power != 
FB_BLANK_UNBLANK)
./drivers/video/backlight/adp8860_bl.c-         brightness = 0;
./drivers/video/backlight/adp8860_bl.c-
./drivers/video/backlight/adp8860_bl.c: if (bl->props.fb_blank != 
FB_BLANK_UNBLANK)
./drivers/video/backlight/adp8860_bl.c-         brightness = 0;
--
./drivers/video/backlight/hp680_bl.c-   if (bd->props.power != 
FB_BLANK_UNBLANK)
./drivers/video/backlight/hp680_bl.c-           intensity = 0;
./drivers/video/backlight/hp680_bl.c:   if (bd->props.fb_blank != 
FB_BLANK_UNBLANK)
./drivers/video/backlight/hp680_bl.c-           intensity = 0;
--
./drivers/video/backlight/cr_bllcd.c-static int 
cr_backlight_set_intensity(struct backlight_device *bd)
./drivers/video/backlight/cr_bllcd.c-{
./drivers/video/backlight/cr_bllcd.c-   int intensity = 
bd->props.brightness;
./drivers/video/backlight/cr_bllcd.c-   u32 addr = gpio_bar + 
CRVML_PANEL_PORT;
./drivers/video/backlight/cr_bllcd.c-   u32 cur = inl(addr);
./drivers/video/backlight/cr_bllcd.c-
./drivers/video/backlight/cr_bllcd.c-   if (bd->props.power == 
FB_BLANK_UNBLANK)
./drivers/video/backlight/cr_bllcd.c-           intensity = 
FB_BLANK_UNBLANK;
./drivers/video/backlight/cr_bllcd.c:   if (bd->props.fb_blank == 
FB_BLANK_UNBLANK)
./drivers/video/backlight/cr_bllcd.c-           intensity = 
FB_BLANK_UNBLANK;
./drivers/video/backlight/cr_bllcd.c-   if (bd->props.power == 
FB_BLANK_POWERDOWN)
./drivers/video/backlight/cr_bllcd.c-           intensity = 
FB_BLANK_POWERDOWN;
./drivers/video/backlight/cr_bllcd.c:   if (bd->props.fb_blank == 
FB_BLANK_POWERDOWN)
./drivers/video/backlight/cr_bllcd.c-           intensity = 
FB_BLANK_POWERDOWN;
--
./drivers/video/backlight/max8925_bl.c- if (bl->props.power != 
FB_BLANK_UNBLANK)
./drivers/video/backlight/max8925_bl.c-         brightness = 0;
./drivers/video/backlight/max8925_bl.c-
./drivers/video/backlight/max8925_bl.c: if (bl->props.fb_blank != 
FB_BLANK_UNBLANK)
./drivers/video/backlight/max8925_bl.c-         brightness = 0;
./drivers/video/backlight/max8925_bl.c-
./drivers/video/backlight/max8925_bl.c- if (bl->props.state & 
BL_CORE_SUSPENDED)
./drivers/video/backlight/max8925_bl.c-         brightness = 0;
--
./drivers/video/backlight/lv5207lp.c-   if (backlight->props.power != 
FB_BLANK_UNBLANK ||
./drivers/video/backlight/lv5207lp.c: backlight->props.fb_blank != 
FB_BLANK_UNBLANK ||
./drivers/video/backlight/lv5207lp.c- backlight->props.state & 
(BL_CORE_SUSPENDED | BL_CORE_FBBLANK))
./drivers/video/backlight/lv5207lp.c-           brightness = 0;
--
./drivers/video/backlight/lm3533_bl.c-  if (bd->props.power != 
FB_BLANK_UNBLANK)
./drivers/video/backlight/lm3533_bl.c-          brightness = 0;
./drivers/video/backlight/lm3533_bl.c:  if (bd->props.fb_blank != 
FB_BLANK_UNBLANK)
./drivers/video/backlight/lm3533_bl.c-          brightness = 0;
--
./drivers/video/backlight/omap1_bl.c-static int 
omapbl_update_status(struct backlight_device *dev)
./drivers/video/backlight/omap1_bl.c-{
./drivers/video/backlight/omap1_bl.c-   struct omap_backlight *bl = 
bl_get_data(dev);
./drivers/video/backlight/omap1_bl.c-
./drivers/video/backlight/omap1_bl.c-   if (bl->current_intensity != 
dev->props.brightness) {
./drivers/video/backlight/omap1_bl.c-           if (bl->powermode == 
FB_BLANK_UNBLANK)
./drivers/video/backlight/omap1_bl.c- 
omapbl_send_intensity(dev->props.brightness);
./drivers/video/backlight/omap1_bl.c- bl->current_intensity = 
dev->props.brightness;
./drivers/video/backlight/omap1_bl.c-   }
./drivers/video/backlight/omap1_bl.c-
./drivers/video/backlight/omap1_bl.c:   if (dev->props.fb_blank != 
bl->powermode)
./drivers/video/backlight/omap1_bl.c: omapbl_set_power(dev, 
dev->props.fb_blank);
./drivers/video/backlight/omap1_bl.c-
./drivers/video/backlight/omap1_bl.c-   return 0;
./drivers/video/backlight/omap1_bl.c-}
./drivers/video/backlight/omap1_bl.c-
--
./drivers/video/backlight/kb3886_bl.c-  if (bd->props.power != 
FB_BLANK_UNBLANK)
./drivers/video/backlight/kb3886_bl.c-          intensity = 0;
./drivers/video/backlight/kb3886_bl.c:  if (bd->props.fb_blank != 
FB_BLANK_UNBLANK)
./drivers/video/backlight/kb3886_bl.c-          intensity = 0;
--
./drivers/video/backlight/pwm_bl.c-     if (bl->props.power != 
FB_BLANK_UNBLANK ||
./drivers/video/backlight/pwm_bl.c:         bl->props.fb_blank != 
FB_BLANK_UNBLANK ||
./drivers/video/backlight/pwm_bl.c-         bl->props.state & 
BL_CORE_FBBLANK)
./drivers/video/backlight/pwm_bl.c-             brightness = 0;
--
./drivers/video/backlight/pm8941-wled.c-        if (bl->props.power != 
FB_BLANK_UNBLANK ||
./drivers/video/backlight/pm8941-wled.c: bl->props.fb_blank != 
FB_BLANK_UNBLANK ||
./drivers/video/backlight/pm8941-wled.c- bl->props.state & BL_CORE_FBBLANK)
./drivers/video/backlight/pm8941-wled.c-                val = 0;
--
./drivers/video/backlight/adp8870_bl.c- if (bl->props.power != 
FB_BLANK_UNBLANK)
./drivers/video/backlight/adp8870_bl.c-         brightness = 0;
./drivers/video/backlight/adp8870_bl.c-
./drivers/video/backlight/adp8870_bl.c: if (bl->props.fb_blank != 
FB_BLANK_UNBLANK)
./drivers/video/backlight/adp8870_bl.c-         brightness = 0;
--
./drivers/video/backlight/as3711_bl.c-  if (bl->props.power != 
FB_BLANK_UNBLANK ||
./drivers/video/backlight/as3711_bl.c:      bl->props.fb_blank != 
FB_BLANK_UNBLANK ||
./drivers/video/backlight/as3711_bl.c-      bl->props.state & 
(BL_CORE_SUSPENDED | BL_CORE_FBBLANK))
./drivers/video/backlight/as3711_bl.c-          brightness = 0;
--
./drivers/video/backlight/88pm860x_bl.c-        if (bl->props.power != 
FB_BLANK_UNBLANK)
./drivers/video/backlight/88pm860x_bl.c-                brightness = 0;
./drivers/video/backlight/88pm860x_bl.c-
./drivers/video/backlight/88pm860x_bl.c:        if (bl->props.fb_blank 
!= FB_BLANK_UNBLANK)
./drivers/video/backlight/88pm860x_bl.c-                brightness = 0;
./drivers/video/backlight/88pm860x_bl.c-
./drivers/video/backlight/88pm860x_bl.c-        if (bl->props.state & 
BL_CORE_SUSPENDED)
./drivers/video/backlight/88pm860x_bl.c-                brightness = 0;
--
./drivers/video/backlight/tps65217_bl.c-        if (bl->props.state & 
BL_CORE_SUSPENDED)
./drivers/video/backlight/tps65217_bl.c-                brightness = 0;
./drivers/video/backlight/tps65217_bl.c-
./drivers/video/backlight/tps65217_bl.c-        if ((bl->props.power != 
FB_BLANK_UNBLANK) ||
./drivers/video/backlight/tps65217_bl.c: (bl->props.fb_blank != 
FB_BLANK_UNBLANK))
./drivers/video/backlight/tps65217_bl.c-                /* framebuffer 
in low power mode or blanking active */
./drivers/video/backlight/tps65217_bl.c-                brightness = 0;
--
./drivers/video/backlight/adp5520_bl.c- if (bl->props.power != 
FB_BLANK_UNBLANK)
./drivers/video/backlight/adp5520_bl.c-         brightness = 0;
./drivers/video/backlight/adp5520_bl.c-
./drivers/video/backlight/adp5520_bl.c: if (bl->props.fb_blank != 
FB_BLANK_UNBLANK)
./drivers/video/backlight/adp5520_bl.c-         brightness = 0;
--
./drivers/video/backlight/wm831x_bl.c-  if (bl->props.power != 
FB_BLANK_UNBLANK)
./drivers/video/backlight/wm831x_bl.c-          brightness = 0;
./drivers/video/backlight/wm831x_bl.c-
./drivers/video/backlight/wm831x_bl.c:  if (bl->props.fb_blank != 
FB_BLANK_UNBLANK)
./drivers/video/backlight/wm831x_bl.c-          brightness = 0;
./drivers/video/backlight/wm831x_bl.c-
./drivers/video/backlight/wm831x_bl.c-  if (bl->props.state & 
BL_CORE_SUSPENDED)
./drivers/video/backlight/wm831x_bl.c-          brightness = 0;
--
./drivers/video/backlight/gpio_backlight.c-     if (bl->props.power != 
FB_BLANK_UNBLANK ||
./drivers/video/backlight/gpio_backlight.c: bl->props.fb_blank != 
FB_BLANK_UNBLANK ||
./drivers/video/backlight/gpio_backlight.c- bl->props.state & 
(BL_CORE_SUSPENDED | BL_CORE_FBBLANK))
./drivers/video/backlight/gpio_backlight.c-             brightness = 0;
--
./drivers/video/backlight/da903x_bl.c-  if (bl->props.power != 
FB_BLANK_UNBLANK)
./drivers/video/backlight/da903x_bl.c-          brightness = 0;
./drivers/video/backlight/da903x_bl.c-
./drivers/video/backlight/da903x_bl.c:  if (bl->props.fb_blank != 
FB_BLANK_UNBLANK)
./drivers/video/backlight/da903x_bl.c-          brightness = 0;
./drivers/video/backlight/da903x_bl.c-
./drivers/video/backlight/da903x_bl.c-  if (bl->props.state & 
BL_CORE_SUSPENDED)
./drivers/video/backlight/da903x_bl.c-          brightness = 0;
--
./drivers/video/backlight/locomolcd.c-  if (bd->props.power != 
FB_BLANK_UNBLANK)
./drivers/video/backlight/locomolcd.c-          intensity = 0;
./drivers/video/backlight/locomolcd.c:  if (bd->props.fb_blank != 
FB_BLANK_UNBLANK)
./drivers/video/backlight/locomolcd.c-          intensity = 0;
--
./drivers/video/backlight/bd6107.c-     if (backlight->props.power != 
FB_BLANK_UNBLANK ||
./drivers/video/backlight/bd6107.c: backlight->props.fb_blank != 
FB_BLANK_UNBLANK ||
./drivers/video/backlight/bd6107.c- backlight->props.state & 
(BL_CORE_SUSPENDED | BL_CORE_FBBLANK))
./drivers/video/backlight/bd6107.c-             brightness = 0;
--
./drivers/video/backlight/backlight.c-                  if (fb_blank == 
FB_BLANK_UNBLANK &&
./drivers/video/backlight/backlight.c- !bd->fb_bl_on[node]) {
./drivers/video/backlight/backlight.c- bd->fb_bl_on[node] = true;
./drivers/video/backlight/backlight.c-                          if 
(!bd->use_count++) {
./drivers/video/backlight/backlight.c- bd->props.state &= ~BL_CORE_FBBLANK;
./drivers/video/backlight/backlight.c: bd->props.fb_blank = 
FB_BLANK_UNBLANK;
./drivers/video/backlight/backlight.c- backlight_update_status(bd);
./drivers/video/backlight/backlight.c-                          }
./drivers/video/backlight/backlight.c-                  } else if 
(fb_blank != FB_BLANK_UNBLANK &&
./drivers/video/backlight/backlight.c- bd->fb_bl_on[node]) {
./drivers/video/backlight/backlight.c- bd->fb_bl_on[node] = false;
./drivers/video/backlight/backlight.c-                          if 
(!(--bd->use_count)) {
./drivers/video/backlight/backlight.c- bd->props.state |= BL_CORE_FBBLANK;
./drivers/video/backlight/backlight.c: bd->props.fb_blank = fb_blank;
./drivers/video/backlight/backlight.c- backlight_update_status(bd);
--
./drivers/video/backlight/ep93xx_bl.c-  if (bl->props.power != 
FB_BLANK_UNBLANK ||
./drivers/video/backlight/ep93xx_bl.c:      bl->props.fb_blank != 
FB_BLANK_UNBLANK)
./drivers/video/backlight/ep93xx_bl.c-          brightness = 0;
--
./drivers/video/backlight/jornada720_bl.c:      if ((bd->props.power != 
FB_BLANK_UNBLANK) || (bd->props.fb_blank != FB_BLANK_UNBLANK)) {
--
./drivers/video/fbdev/omap2/omapfb/displays/panel-dsi-cm.c:     if 
(dev->props.fb_blank == FB_BLANK_UNBLANK &&
./drivers/video/fbdev/omap2/omapfb/displays/panel-dsi-cm.c- 
dev->props.power == FB_BLANK_UNBLANK)
./drivers/video/fbdev/omap2/omapfb/displays/panel-dsi-cm.c- level = 
dev->props.brightness;
./drivers/video/fbdev/omap2/omapfb/displays/panel-dsi-cm.c-     else
./drivers/video/fbdev/omap2/omapfb/displays/panel-dsi-cm.c- level = 0;
--
./drivers/video/fbdev/omap2/omapfb/displays/panel-sony-acx565akm.c: if 
(dev->props.fb_blank == FB_BLANK_UNBLANK &&
./drivers/video/fbdev/omap2/omapfb/displays/panel-sony-acx565akm.c- 
dev->props.power == FB_BLANK_UNBLANK)
./drivers/video/fbdev/omap2/omapfb/displays/panel-sony-acx565akm.c- 
level = dev->props.brightness;
./drivers/video/fbdev/omap2/omapfb/displays/panel-sony-acx565akm.c- else
./drivers/video/fbdev/omap2/omapfb/displays/panel-sony-acx565akm.c- 
level = 0;
--
./drivers/video/fbdev/aty/atyfb_base.c- if (bd->props.power != 
FB_BLANK_UNBLANK ||
./drivers/video/fbdev/aty/atyfb_base.c:     bd->props.fb_blank != 
FB_BLANK_UNBLANK)
./drivers/video/fbdev/aty/atyfb_base.c-         level = 0;
./drivers/video/fbdev/aty/atyfb_base.c- else
./drivers/video/fbdev/aty/atyfb_base.c-         level = 
bd->props.brightness;
--
./drivers/video/fbdev/aty/aty128fb.c-   if (bd->props.power != 
FB_BLANK_UNBLANK ||
./drivers/video/fbdev/aty/aty128fb.c:       bd->props.fb_blank != 
FB_BLANK_UNBLANK ||
./drivers/video/fbdev/aty/aty128fb.c-       !par->lcd_on)
./drivers/video/fbdev/aty/aty128fb.c-           level = 0;
./drivers/video/fbdev/aty/aty128fb.c-   else
./drivers/video/fbdev/aty/aty128fb.c-           level = 
bd->props.brightness;
--
./drivers/video/fbdev/aty/radeon_backlight.c-        if (bd->props.power 
!= FB_BLANK_UNBLANK ||
./drivers/video/fbdev/aty/radeon_backlight.c: bd->props.fb_blank != 
FB_BLANK_UNBLANK)
./drivers/video/fbdev/aty/radeon_backlight.c-           level = 0;
./drivers/video/fbdev/aty/radeon_backlight.c-   else
./drivers/video/fbdev/aty/radeon_backlight.c-           level = 
bd->props.brightness;
--
./drivers/video/fbdev/mx3fb.c-  if (bl->props.power != FB_BLANK_UNBLANK)
./drivers/video/fbdev/mx3fb.c-          brightness = 0;
./drivers/video/fbdev/mx3fb.c:  if (bl->props.fb_blank != FB_BLANK_UNBLANK)
./drivers/video/fbdev/mx3fb.c-          brightness = 0;
--
./drivers/video/fbdev/riva/fbdev.c-     if (bd->props.power != 
FB_BLANK_UNBLANK ||
./drivers/video/fbdev/riva/fbdev.c:         bd->props.fb_blank != 
FB_BLANK_UNBLANK)
./drivers/video/fbdev/riva/fbdev.c-             level = 0;
./drivers/video/fbdev/riva/fbdev.c-     else
./drivers/video/fbdev/riva/fbdev.c-             level = 
bd->props.brightness;
--
./drivers/video/fbdev/atmel_lcdfb.c:    if (bl->props.fb_blank != 
sinfo->bl_power)
./drivers/video/fbdev/atmel_lcdfb.c:            power = bl->props.fb_blank;
./drivers/video/fbdev/atmel_lcdfb.c-    else if (bl->props.power != 
sinfo->bl_power)
./drivers/video/fbdev/atmel_lcdfb.c-            power = bl->props.power;
--
./drivers/video/fbdev/nvidia/nv_backlight.c-    if (bd->props.power != 
FB_BLANK_UNBLANK ||
./drivers/video/fbdev/nvidia/nv_backlight.c: bd->props.fb_blank != 
FB_BLANK_UNBLANK)
./drivers/video/fbdev/nvidia/nv_backlight.c-            level = 0;
./drivers/video/fbdev/nvidia/nv_backlight.c-    else
./drivers/video/fbdev/nvidia/nv_backlight.c-            level = 
bd->props.brightness;
--
./drivers/macintosh/via-pmu-backlight.c-        if (bd->props.power != 
FB_BLANK_UNBLANK ||
./drivers/macintosh/via-pmu-backlight.c: bd->props.fb_blank != 
FB_BLANK_UNBLANK)
./drivers/macintosh/via-pmu-backlight.c-                level = 0;
--
./drivers/gpu/drm/omapdrm/displays/panel-dsi-cm.c:      if 
(dev->props.fb_blank == FB_BLANK_UNBLANK &&
./drivers/gpu/drm/omapdrm/displays/panel-dsi-cm.c- dev->props.power == 
FB_BLANK_UNBLANK)
./drivers/gpu/drm/omapdrm/displays/panel-dsi-cm.c- level = 
dev->props.brightness;
./drivers/gpu/drm/omapdrm/displays/panel-dsi-cm.c-      else
./drivers/gpu/drm/omapdrm/displays/panel-dsi-cm.c- level = 0;
--
./drivers/gpu/drm/omapdrm/displays/panel-sony-acx565akm.c:      if 
(dev->props.fb_blank == FB_BLANK_UNBLANK &&
./drivers/gpu/drm/omapdrm/displays/panel-sony-acx565akm.c- 
dev->props.power == FB_BLANK_UNBLANK)
./drivers/gpu/drm/omapdrm/displays/panel-sony-acx565akm.c- level = 
dev->props.brightness;
./drivers/gpu/drm/omapdrm/displays/panel-sony-acx565akm.c-      else
./drivers/gpu/drm/omapdrm/displays/panel-sony-acx565akm.c- level = 0;
--
./drivers/staging/fbtft/fb_ssd1351.c-   on = (bd->props.power == 
FB_BLANK_UNBLANK) &&
./drivers/staging/fbtft/fb_ssd1351.c:        (bd->props.fb_blank == 
FB_BLANK_UNBLANK);
--
./drivers/staging/fbtft/fbtft-core.c-   if ((bd->props.power == 
FB_BLANK_UNBLANK) &&
./drivers/staging/fbtft/fbtft-core.c:       (bd->props.fb_blank == 
FB_BLANK_UNBLANK))
--
./drivers/staging/fbtft/fb_watterott.c- if (bd->props.power != 
FB_BLANK_UNBLANK)
./drivers/staging/fbtft/fb_watterott.c-         brightness = 0;
./drivers/staging/fbtft/fb_watterott.c-
./drivers/staging/fbtft/fb_watterott.c: if (bd->props.fb_blank != 
FB_BLANK_UNBLANK)
./drivers/staging/fbtft/fb_watterott.c-         brightness = 0;
--
./drivers/auxdisplay/ht16k33.c- if (bl->props.power != FB_BLANK_UNBLANK ||
./drivers/auxdisplay/ht16k33.c:     bl->props.fb_blank != 
FB_BLANK_UNBLANK ||
./drivers/auxdisplay/ht16k33.c-     bl->props.state & BL_CORE_FBBLANK || 
brightness == 0) {
./drivers/auxdisplay/ht16k33.c-         return ht16k33_display_off(priv);
--
./drivers/platform/x86/thinkpad_acpi.c: (bd->props.fb_blank == 
FB_BLANK_UNBLANK &&
./drivers/platform/x86/thinkpad_acpi.c-          bd->props.power == 
FB_BLANK_UNBLANK) ?
./drivers/platform/x86/thinkpad_acpi.c- bd->props.brightness : 0;
--
./drivers/platform/x86/acer-wmi.c-      if (bd->props.power != 
FB_BLANK_UNBLANK)
./drivers/platform/x86/acer-wmi.c-              intensity = 0;
./drivers/platform/x86/acer-wmi.c:      if (bd->props.fb_blank != 
FB_BLANK_UNBLANK)
./drivers/platform/x86/acer-wmi.c-              intensity = 0;

>
> Daniel.
>
>
>> ---
>>   include/linux/backlight.h | 30 ++++++++++++++++++++++++++++++
>>   1 file changed, 30 insertions(+)
>>
>> diff --git a/include/linux/backlight.h b/include/linux/backlight.h
>> index af7003548..7b6a9a2a3 100644
>> --- a/include/linux/backlight.h
>> +++ b/include/linux/backlight.h
>> @@ -130,6 +130,36 @@ static inline int backlight_update_status(struct 
>> backlight_device *bd)
>>       return ret;
>>   }
>>   +/**
>> +  * backlight_enable - Enable backlight
>> +  * @bd: the backlight device to enable
>> +  */
>> +static inline int backlight_enable(struct backlight_device *bd)
>> +{
>> +    if (!bd)
>> +        return 0;
>> +
>> +    bd->props.power = FB_BLANK_UNBLANK;
>> +    bd->props.state &= ~BL_CORE_FBBLANK;
>> +
>> +    return backlight_update_status(bd);
>> +}
>> +
>> +/**
>> +  * backlight_disable - Disable backlight
>> +  * @bd: the backlight device to disable
>> +  */
>> +static inline int backlight_disable(struct backlight_device *bd)
>> +{
>> +    if (!bd)
>> +        return 0;
>> +
>> +    bd->props.power = FB_BLANK_POWERDOWN;
>> +    bd->props.state |= BL_CORE_FBBLANK;
>> +
>> +    return backlight_update_status(bd);
>> +}
>> +
>>   extern struct backlight_device *backlight_device_register(const 
>> char *name,
>>       struct device *dev, void *devdata, const struct backlight_ops 
>> *ops,
>>       const struct backlight_properties *props);
>>