Re: [PATCH v3] media: v4l2-flash: Enter LED off state after file handle closed

[Sakari Ailus]

Hi Jacek,

On Sat, Feb 21, 2026 at 04:48:48PM +0100, Jacek Anaszewski wrote:
> Hi ChiYuan,
> 
> On 1/12/26 10:20, cy_huang@xxxxxxxxxxx wrote:
> > From: ChiYuan Huang <cy_huang@xxxxxxxxxxx>
> > 
> > To make sure LED enter off state after file handle is closed, initiatively
> > configure LED_MODE to NONE. This can guarantee whatever the previous state
> > is torch or strobe mode, the final state will be off.
> > 
> > Cc: stable@xxxxxxxxxxxxxxx
> > Fixes: 42bd6f59ae90 ("media: Add registration helpers for V4L2 flash sub-devices")
> > Signed-off-by: ChiYuan Huang <cy_huang@xxxxxxxxxxx>
> > ---
> > Still cannot pass patch integration check, send v3 patch to fix all.
> > 
> > v3
> > - Remove 'Reported-by' tag
> > - Fix identation check for patch integration
> > 
> > v2
> > - Fix commit message redudant space cause patch robot parsing error
> > 
> > Hi,
> >    We encounter an issue. When the upper layer camera process is crashed,
> > if the new process did not reinit the LED,  it will keeps the previous
> > state whatever it's in torch or strobe mode
> > 
> > OS will handle the resource management. So when the process is crashed
> > or terminated, the 'close' API will be called to release resources.
> > That's why we add the initiative action to trigger LED off in file
> > handle close is called.
> > ---
> >   drivers/media/v4l2-core/v4l2-flash-led-class.c | 6 ++++++
> >   1 file changed, 6 insertions(+)
> > 
> > diff --git a/drivers/media/v4l2-core/v4l2-flash-led-class.c b/drivers/media/v4l2-core/v4l2-flash-led-class.c
> > index 355595a0fefa..46606f5cc192 100644
> > --- a/drivers/media/v4l2-core/v4l2-flash-led-class.c
> > +++ b/drivers/media/v4l2-core/v4l2-flash-led-class.c
> > @@ -623,6 +623,12 @@ static int v4l2_flash_close(struct v4l2_subdev *sd, struct v4l2_subdev_fh *fh)
> >   		return 0;
> >   	if (led_cdev) {
> > +		/* If file handle is released, make sure LED enter off state */
> > +		ret = v4l2_ctrl_s_ctrl(v4l2_flash->ctrls[LED_MODE],
> > +				       V4L2_FLASH_LED_MODE_NONE);
> > +		if (ret)
> > +			return ret;
> > +
> >   		mutex_lock(&led_cdev->led_access);
> >   		if (v4l2_flash->ctrls[STROBE_SOURCE])
> > 
> > base-commit: 8ac28a6642d1cc8bac0632222e66add800b027fa
> 
> The patch itself looks good, but while at it I started wondering
> if we shouldn't move below STROBE_SOURCE access before the lock.
> I don't see now, why we placed it there.
> 
> Adding Sakari.

Thanks for cc'ing me.

The behaviour this patch changes has been around for a decade or so. I
wonder what breaks if we change it now. It works the same way as the sysfs
LED API, too, and I think common behaviour between the two APIs was the
reasoning back then as well.

-- 
Kind regards,

Sakari Ailus