On Wednesday, June 22, 2011 14:38:55 Jonathan Corbet wrote: > On Wed, 22 Jun 2011 11:43:14 +0200 > Marek Szyprowski <m.szyprowski@xxxxxxxxxxx> wrote: > > > > Do you really need a flag? If a driver absolutely cannot stream without > > > buffers queued (and can't be fixed to start streaming for real when the > > > buffers show up) it should just return -EINVAL from start_streaming() or > > > some such. The driver must be aware of its limitations regardless, but > > > there's no need to push that awareness into vb2 as well. > > > > The main idea behind vb2 was to move all common error handling code to > > the framework and provide simple functions that can be used by the driver > > directly without the need for additional checks. > > For stuff that's truly common, that makes sense. As soon as you start > adding driver-specific flags, things aren't quite so common anymore. In > this case, the driver writer can just as easily check the state of the > buffer queue at streamon time, so I don't see what would be gained. > Whatever, doesn't matter that much. > > > > (FWIW, I wouldn't switch the order of operations in vb2_streamon(); I > > > would just take out the "if (q->streaming)" test at the end of vb2_qbuf() > > > and pass the buffers through directly. But maybe that's just me.) > > > > I want to keep the current version of vb2_qbuf() and change the order of > > operations in streamon(). > > I'm curious as to why? As far as I can tell, there's no reason not to > pass the buffers straight through when you get them? I'm curious as well. I don't see the problem with that. > > The only problem that still need to be resolved is what should happen with > > the buffers if start_streaming() fails. The ownership for these buffers have > > been already given to the driver, but they might have been in dirty state. > > Probably vb2 should assume that the buffers are lost and reinitialize them. > > You already grab them back at stop_streaming() time, right? I'd think > that a failed start_streaming() should leave things in exactly the same > state as a start/stop_streaming() sequence. I think so too. vb2 can just call queue_cancel, I think. Regards, Hans > > Thanks, > > jon > -- > To unsubscribe from this list: send the line "unsubscribe linux-media" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
