Oliver Neukum wrote: > > > Rather make this per open than per device. As is, it will really hurt > > performance with multiple capturing opens (or doesn't v4l1 allow > > this?). Can't the driver implement it's own semaphore if it needs it? > > Multiple opens are impossible under v4l. > However multithreaded tasks could do concurrent reads or writes. > This is not intended I think, thus the semaphores. > It's hard to see how the hardware could do several reads at the same time. > Thus v4l can do this for the drivers. This is a race that hits 2/3 of the usb > video devices. > > Regards > Oliver I can see the problem, but I personally think that this should be handled by the driver itself. If the driver can handle simultaneous (for example, separate even/odd fileds) reads, let it, otherwise let it serialise the operations itself. As usual, this is just IMHO, but I think the idea of videodev.c was to be a pretty lightweight wrapper, with the driver doing all the real work. -justin
