Em 01-07-2011 08:59, Mauro Carvalho Chehab escreveu: > Em 01-07-2011 06:45, Hans Verkuil escreveu: >> On Thursday, June 30, 2011 22:35:15 Mauro Carvalho Chehab wrote: > >>>> This also leads to another ambiguity with poll(): what should poll do if >>>> another filehandle started streaming? So fh1 called STREAMON (and so becomes >>>> the 'owner' of the stream), and you poll on fh2. If a frame becomes available, >>>> should fh2 wake up? Is fh2 allowed to call DQBUF? >>> >>> IMO, both fh's should get the same results. This is what happens if you're >>> writing into a file and two or more processes are selecting at the EOF. >> >> Yes, but multiple filehandles are allowed to write/read from a file at the >> same time. That's not true for V4L2. Only one filehandle can do I/O at a time. > > Actually, this is not quite true currently, as you could, for example use one fd > for QBUF, and another for DQBUF, with the current behavior, but, with luck, > no applications are doing weird things like that. Yet, tests are needed to avoid > breaking something, if we're willing to change it. > >> I'm going to look into changing fs/select.c so that the poll driver function >> can actually see the event mask provided by the application. > > Why? A POLLERR should be notified, whatever mask is there, as the application > may need to abort (for example, in cases like hardware removal). I was too quick on my last comment. Your patch is clear: you want to start it only if the poll mask has "in" or "out" file descriptiors. Ok, this makes sense to me. Cheers, Mauro -- 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
