On Tuesday, November 12, 2013 8:57 AM, Kyungmin Park wrote:
>
> From: Kyungmin Park <kyungmin.park@xxxxxxxxxxx>
>
> The most mobile phones have Ambient Light Sensors and it changes brightness according lux.
> It means it changes backlight brightness frequently by just writing sysfs node, so it generates uevent.
>
> Usually there's no user to use this backlight changes. But it forks udev worker threads and it takes
> about 5ms. The main problem is that it hurts other process activities. so remove it.
>
> Kay said
> "Uevents are for the major, low-frequent, global device state-changes,
> not for carrying-out any sort of measurement data. Subsystems which
> need that should use other facilities like poll()-able sysfs file or
> any other subscription-based, client-tracking interface which does not
> cause overhead if it isn't used. Uevents are not the right thing to
> use here, and upstream udev should not paper-over broken kernel
> subsystems."
>
> Signed-off-by: Kyungmin Park <kyungmin.park@xxxxxxxxxxx>
> ---
> diff --git a/drivers/video/backlight/backlight.c b/drivers/video/backlight/backlight.c
> index 94a403a..441272d 100644
> --- a/drivers/video/backlight/backlight.c
> +++ b/drivers/video/backlight/backlight.c
> @@ -88,9 +88,6 @@ static void backlight_generate_event(struct backlight_device *bd,
> char *envp[2];
>
> switch (reason) {
> - case BACKLIGHT_UPDATE_SYSFS:
> - envp[0] = "SOURCE=sysfs";
> - break;
> case BACKLIGHT_UPDATE_HOTKEY:
> envp[0] = "SOURCE=hotkey";
> break;
> @@ -172,8 +169,6 @@ static ssize_t brightness_store(struct device *dev,
> }
> mutex_unlock(&bd->ops_lock);
>
> - backlight_generate_event(bd, BACKLIGHT_UPDATE_SYSFS);
> -
> return rc;
> }
> static DEVICE_ATTR_RW(brightness);
> diff --git a/include/linux/backlight.h b/include/linux/backlight.h
> index 53b7794..d2a27dd 100644
> --- a/include/linux/backlight.h
> +++ b/include/linux/backlight.h
> @@ -29,7 +29,6 @@
>
> enum backlight_update_reason {
> BACKLIGHT_UPDATE_HOTKEY,
> - BACKLIGHT_UPDATE_SYSFS,
+cc Henrique de Moraes Holschuh (Maintainer of thinkpad_acpi)
Hi Henrique de Moraes Holschuh,
'thinkpad_acpi.c' uses the 'BACKLIGHT_UPDATE_SYSFS'.
Henrique, can we remove it?
drivers/platform/x86/thinkpad_acpi.c
if (!rc && ibm_backlight_device)
backlight_force_update(ibm_backlight_device,
BACKLIGHT_UPDATE_SYSFS);
Best regards,
Jingoo Han
> };
>
> enum backlight_type {
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