On Tuesday 16 November 2010, Hans Verkuil wrote:
> A pointer to this struct is available in vdev->v4l2_dev. However, not all
> drivers implement struct v4l2_device. But on the other hand, most relevant
> drivers do. So as a fallback we would still need a static mutex.
Wouldn't that suffer the same problem as putting the mutex into videodev
as I suggested? You said that there are probably drivers that need to
serialize between multiple devices, so if we have a mutex per v4l2_device,
you can still get races between multiple ioctl calls accessing the same
per-driver data. To solve this, we'd have to put the lock into a per-driver
structure like v4l2_file_operations or v4l2_ioctl_ops, which would add
to the ugliness.
Arnd
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