| Message ID | 1495054507-9988-1-git-send-email-sudipm.mukherjee@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Wed, 17 May 2017, Sudip Mukherjee wrote: > It is possible to update the backlight power and the brightness using > the sysfs and on writing it either returns the count or if the callback > function does not exist then returns the error code 'ENXIO'. > > We have a situation where the userspace client is writing to the sysfs > to update the power and since the callback function exists the client > receives the return value as count and considers the operation to be > successful. That is correct as the write to the sysfs was successful. > But there is no way to know if the actual operation was done or not. > > backlight_update_status() returns the error code if it fails. Pass that > to the userspace client who is trying to update the power so that the > client knows that the operation failed. > > Acked-by: Daniel Thompson <daniel.thompson@linaro.org> > Signed-off-by: Sudip Mukherjee <sudip.mukherjee@codethink.co.uk> > --- > > v5: dropped the ternary condition > v4: ABI comment removed from commit message > v3: remove rc = 0, and update rc with count in else condition. > v2: update power with old value on failure. > > drivers/video/backlight/backlight.c | 15 ++++++++++----- > 1 file changed, 10 insertions(+), 5 deletions(-) Applied, thanks. > diff --git a/drivers/video/backlight/backlight.c b/drivers/video/backlight/backlight.c > index 288318a..8049e76 100644 > --- a/drivers/video/backlight/backlight.c > +++ b/drivers/video/backlight/backlight.c > @@ -134,7 +134,7 @@ static ssize_t bl_power_store(struct device *dev, struct device_attribute *attr, > { > int rc; > struct backlight_device *bd = to_backlight_device(dev); > - unsigned long power; > + unsigned long power, old_power; > > rc = kstrtoul(buf, 0, &power); > if (rc) > @@ -145,10 +145,16 @@ static ssize_t bl_power_store(struct device *dev, struct device_attribute *attr, > if (bd->ops) { > pr_debug("set power to %lu\n", power); > if (bd->props.power != power) { > + old_power = bd->props.power; > bd->props.power = power; > - backlight_update_status(bd); > + rc = backlight_update_status(bd); > + if (rc) > + bd->props.power = old_power; > + else > + rc = count; > + } else { > + rc = count; > } > - rc = count; > } > mutex_unlock(&bd->ops_lock); > > @@ -176,8 +182,7 @@ int backlight_device_set_brightness(struct backlight_device *bd, > else { > pr_debug("set brightness to %lu\n", brightness); > bd->props.brightness = brightness; > - backlight_update_status(bd); > - rc = 0; > + rc = backlight_update_status(bd); > } > } > mutex_unlock(&bd->ops_lock);
diff --git a/drivers/video/backlight/backlight.c b/drivers/video/backlight/backlight.c index 288318a..8049e76 100644 --- a/drivers/video/backlight/backlight.c +++ b/drivers/video/backlight/backlight.c @@ -134,7 +134,7 @@ static ssize_t bl_power_store(struct device *dev, struct device_attribute *attr, { int rc; struct backlight_device *bd = to_backlight_device(dev); - unsigned long power; + unsigned long power, old_power; rc = kstrtoul(buf, 0, &power); if (rc) @@ -145,10 +145,16 @@ static ssize_t bl_power_store(struct device *dev, struct device_attribute *attr, if (bd->ops) { pr_debug("set power to %lu\n", power); if (bd->props.power != power) { + old_power = bd->props.power; bd->props.power = power; - backlight_update_status(bd); + rc = backlight_update_status(bd); + if (rc) + bd->props.power = old_power; + else + rc = count; + } else { + rc = count; } - rc = count; } mutex_unlock(&bd->ops_lock); @@ -176,8 +182,7 @@ int backlight_device_set_brightness(struct backlight_device *bd, else { pr_debug("set brightness to %lu\n", brightness); bd->props.brightness = brightness; - backlight_update_status(bd); - rc = 0; + rc = backlight_update_status(bd); } } mutex_unlock(&bd->ops_lock);