locking in OMAP ISP subdevs

DISCUSSION Michael Jones 2 participants 2 messages May 9, 2011 Media (V4L/DVB)

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Michael Jones

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2011-05-09 12:38 UTC #0 lore raw

Hi Laurent,

I can't find where the locking is handled for ISP subdev standard ioctls like ccdc_v4l2_pad_ops.set_fmt(). Using the CCDC as an example, it looks to me like the following sequence happens when e.g. format is set on CCDC pad 0:

1. # media-ctl --set-format '"OMAP3 ISP CCDC":0 [Y8 640x480]'

2. v4l2-dev.c:v4l2_ioctl()

this calls vdev->fops->unlocked_ioctl, which was set to v4l2-subdev.c:subdev_ioctl() in "v4l2_subdev_fops" in v4l2-device.c:v4l2_device_register_subdev_nodes()

3. v4l2-subdev.c:subdev_ioctl()
4. video_usercopy()
5. v4l2-ioctl.c:__video_usercopy()
6. v4l2-subdev.c:subdev_do_ioctl()
7. ispccdc.c:ccdc_set_format()

ccdc_set_format() sets ccdc->formats[pad], access to which should be serialized, but I don't see how this happens. In the call sequence above, the only opportunity I see is in (2), but only then if ccdc->subdev.devnode.lock is set, which doesn't seem to be done.

Can you clarify this for me? What mutex is held during a call to ccdc_set_format()?

-Michael

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Laurent Pinchart

2011-05-09 22:27 UTC #1 lore raw

Hi Michael,

Quoted 21 lines · On Monday 09 May 2011 14:32:09 Michael Jones wrote:

Hi Laurent,
I can't find where the locking is handled for ISP subdev standard ioctls like ccdc_v4l2_pad_ops.set_fmt(). Using the CCDC as an example, it looks to me like the following sequence happens when e.g. format is set on CCDC pad 0:
1. # media-ctl --set-format '"OMAP3 ISP CCDC":0 [Y8 640x480]'
2. v4l2-dev.c:v4l2_ioctl()
this calls vdev->fops->unlocked_ioctl, which was set to v4l2-subdev.c:subdev_ioctl() in "v4l2_subdev_fops" in v4l2-device.c:v4l2_device_register_subdev_nodes()
3. v4l2-subdev.c:subdev_ioctl()
4. video_usercopy()
5. v4l2-ioctl.c:__video_usercopy()
6. v4l2-subdev.c:subdev_do_ioctl()
7. ispccdc.c:ccdc_set_format()

Quoted 7 lines

ccdc_set_format() sets ccdc->formats[pad], access to which should be serialized, but I don't see how this happens. In the call sequence above, the only opportunity I see is in (2), but only then if ccdc->subdev.devnode.lock is set, which doesn't seem to be done.
Can you clarify this for me? What mutex is held during a call to ccdc_set_format()?

None. Patches are welcome :-)

Signature · 3 lines

Regards,

Laurent Pinchart