media: i2c: ov5647: Grab [HV]FLIP controls when streaming

[6by9]

The HFLIP and VFLIP controls change the pixel format, so can not be changed whilst streaming.

Grab those controls when starting streaming, and release them when stopping.

Fixes: 7435508 ("media: i2c: ov5647: Support HFLIP and VFLIP")

raspberrypi/libcamera#360

[Kletternaut]

Thanks for the quick response and for preparing the fix so promptly. I really appreciate it!

[6by9]

Thanks for the quick response and for preparing the fix so promptly. I really appreciate it!

This is why I say there's little point pointing AI at it - within the first line of your report I knew what the problem was going to be. A clear description of the issue is worth far more than masses of analysis.

[Kletternaut]

Hey 6by9,
You’re clearly a pro at this—I just wanted to help out as best I could (and keep the extra work to a minimum).

The funny thing is, I had already analyzed the root cause in detail a few weeks ago and it was definitely in the driver; unfortunately, I’d misplaced my notes on it, so I had to quickly go through the process again.

In my prompt, I even mentioned that there was an error in the driver and that I was looking for the cause...
That’s just how things go sometimes.

Tested successfully on my Raspberry Pi 5 with the kernel from sudo rpi-update pulls/7685.

With the OV5647 streaming using --rotation 180, starting a second rpicam-vid instance on the IMX477 no longer changes the OV5647's HFLIP/VFLIP controls or its preview orientation.

The patch fixes the issue in my setup. Thanks again for the quick fix!
Best, Tom

[JamesH65]

Just for my own undersstanding, are these released automagically, rather than needing a specific ungrab?

[6by9]

Just for my own undersstanding, are these released automagically, rather than needing a specific ungrab?

https://elixir.bootlin.com/linux/v7.2.10/source/include/media/v4l2-ctrls.h#L902

/**
 * __v4l2_ctrl_grab() - Unlocked variant of v4l2_ctrl_grab.
 *
 * @ctrl:	The control to (de)activate.
 * @grabbed:	True if the control should become grabbed.
 *
 * This sets or clears the V4L2_CTRL_FLAG_GRABBED flag atomically.
 * Does nothing if @ctrl == NULL.
 * The V4L2_EVENT_CTRL event will be generated afterwards.
 * This will usually be called when starting or stopping streaming in the
 * driver.

grabbed is passed from enable, so 1 when starting streaming and 0 when stopping streaming.

[JamesH65]

Just for my own undersstanding, are these released automagically, rather than needing a specific ungrab?

https://elixir.bootlin.com/linux/v7.2.10/source/include/media/v4l2-ctrls.h#L902

/**
 * __v4l2_ctrl_grab() - Unlocked variant of v4l2_ctrl_grab.
 *
 * @ctrl:	The control to (de)activate.
 * @grabbed:	True if the control should become grabbed.
 *
 * This sets or clears the V4L2_CTRL_FLAG_GRABBED flag atomically.
 * Does nothing if @ctrl == NULL.
 * The V4L2_EVENT_CTRL event will be generated afterwards.
 * This will usually be called when starting or stopping streaming in the
 * driver.

grabbed is passed from enable, so 1 when starting streaming and 0 when stopping streaming.

Gotcha, I'd missed that this function could both start and stop. Ta!