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Message-ID: <52DF5125.3040909@freescale.com>
Date: Wed, 22 Jan 2014 13:03:33 +0800
From: Liu Ying <Ying.Liu@...escale.com>
To: <jg1.han@...sung.com>
CC: <linux-fbdev@...r.kernel.org>,
linux-kernel <linux-kernel@...r.kernel.org>,
DRI mailing list <dri-devel@...ts.freedesktop.org>,
<plagnioj@...osoft.com>, <tomi.valkeinen@...com>
Subject: Re:[PATCH v2] backlight: turn backlight on/off when necessary
Ping...
Regards,
Liu Ying
On 01/20/2014 12:52 PM, Liu Ying wrote:
> We don't have to turn backlight on/off everytime a blanking
> or unblanking event comes because the backlight status may
> have already been what we want. Another thought is that one
> backlight device may be shared by multiple framebuffers. We
> don't hope blanking one of the framebuffers may turn the
> backlight off for all the other framebuffers, since they are
> likely being active to display something. This patch adds
> some logics to record each framebuffer's backlight usage to
> determine the backlight device use count and whether the
> backlight should be turned on or off. To be more specific,
> only one unblank operation on a certain blanked framebuffer
> may increase the backlight device's use count by one, while
> one blank operation on a certain unblanked framebuffer may
> decrease the use count by one, because the userspace is
> likely to unblank a unblanked framebuffer or blank a blanked
> framebuffer.
>
> Signed-off-by: Liu Ying <Ying.Liu@...escale.com>
> ---
> v1 can be found at https://lkml.org/lkml/2013/5/30/139
>
> v1->v2:
> * Make the commit message be more specific about the condition
> in which backlight device use count can be increased/decreased.
> * Correct the setting for bd->props.fb_blank.
>
> drivers/video/backlight/backlight.c | 28 +++++++++++++++++++++-------
> include/linux/backlight.h | 6 ++++++
> 2 files changed, 27 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/video/backlight/backlight.c b/drivers/video/backlight/backlight.c
> index 5d05555..42044be 100644
> --- a/drivers/video/backlight/backlight.c
> +++ b/drivers/video/backlight/backlight.c
> @@ -34,13 +34,15 @@ static const char *const backlight_types[] = {
> defined(CONFIG_BACKLIGHT_CLASS_DEVICE_MODULE))
> /* This callback gets called when something important happens inside a
> * framebuffer driver. We're looking if that important event is blanking,
> - * and if it is, we're switching backlight power as well ...
> + * and if it is and necessary, we're switching backlight power as well ...
> */
> static int fb_notifier_callback(struct notifier_block *self,
> unsigned long event, void *data)
> {
> struct backlight_device *bd;
> struct fb_event *evdata = data;
> + int node = evdata->info->node;
> + int fb_blank = 0;
>
> /* If we aren't interested in this event, skip it immediately ... */
> if (event != FB_EVENT_BLANK && event != FB_EVENT_CONBLANK)
> @@ -51,12 +53,24 @@ static int fb_notifier_callback(struct notifier_block *self,
> if (bd->ops)
> if (!bd->ops->check_fb ||
> bd->ops->check_fb(bd, evdata->info)) {
> - bd->props.fb_blank = *(int *)evdata->data;
> - if (bd->props.fb_blank == FB_BLANK_UNBLANK)
> - bd->props.state &= ~BL_CORE_FBBLANK;
> - else
> - bd->props.state |= BL_CORE_FBBLANK;
> - backlight_update_status(bd);
> + fb_blank = *(int *)evdata->data;
> + if (fb_blank == FB_BLANK_UNBLANK &&
> + !bd->fb_bl_on[node]) {
> + bd->fb_bl_on[node] = true;
> + if (!bd->use_count++) {
> + bd->props.state &= ~BL_CORE_FBBLANK;
> + bd->props.fb_blank = FB_BLANK_UNBLANK;
> + backlight_update_status(bd);
> + }
> + } else if (fb_blank != FB_BLANK_UNBLANK &&
> + bd->fb_bl_on[node]) {
> + bd->fb_bl_on[node] = false;
> + if (!(--bd->use_count)) {
> + bd->props.state |= BL_CORE_FBBLANK;
> + bd->props.fb_blank = FB_BLANK_POWERDOWN;
> + backlight_update_status(bd);
> + }
> + }
> }
> mutex_unlock(&bd->ops_lock);
> return 0;
> diff --git a/include/linux/backlight.h b/include/linux/backlight.h
> index 5f9cd96..7264742 100644
> --- a/include/linux/backlight.h
> +++ b/include/linux/backlight.h
> @@ -9,6 +9,7 @@
> #define _LINUX_BACKLIGHT_H
>
> #include <linux/device.h>
> +#include <linux/fb.h>
> #include <linux/mutex.h>
> #include <linux/notifier.h>
>
> @@ -104,6 +105,11 @@ struct backlight_device {
> struct list_head entry;
>
> struct device dev;
> +
> + /* Multiple framebuffers may share one backlight device */
> + bool fb_bl_on[FB_MAX];
> +
> + int use_count;
> };
>
> static inline void backlight_update_status(struct backlight_device *bd)
> --
> 1.7.9.5
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