Re: [PATCH] video: backlight: Remove backlight sysfs uevent
From: Jingoo Han <hidden>
Date: 2013-11-12 00:18:11
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lkml, platform-driver-x86
On Tuesday, November 12, 2013 8:57 AM, Kyungmin Park wrote:
quoted hunk ↗ jump to hunk
From: Kyungmin Park <kyungmin.park@samsung.com> 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@samsung.com> ---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 {