On Monday, November 22, 2010 11:41:27 Laurent Pinchart wrote: > Hi Hans, > > On Monday 22 November 2010 10:08:06 Hans Verkuil wrote: > > On Monday, November 22, 2010 00:35:54 Laurent Pinchart wrote: > > > Hi Jonathan, > > > > > > I forgot to answer one of your comments. > > > > > > On Wednesday 17 November 2010 01:31:15 Jonathan Corbet wrote: > > > > > > [snip] > > > > > > > > +static unsigned int media_poll(struct file *filp, > > > > > + struct poll_table_struct *poll) > > > > > +{ > > > > > + struct media_devnode *mdev = media_devnode_data(filp); > > > > > + > > > > > + if (!mdev->fops->poll || !media_devnode_is_registered(mdev)) > > > > > + return DEFAULT_POLLMASK; > > > > > + return mdev->fops->poll(filp, poll); > > > > > +} > > > > > > > > If it's not registered, I would expect poll() to return an error. > > > > > > Agreed. I'll return POLLERR | POLLHUP in that case. Is that fine with you > > > ? > > > > When I looked at this for the core code I decided to just return POLLERR. > > I've copied the usbdevfs code which returns POLLERR | POLLHUP when devices > are > disconnected. > > > That seemed to be what the majority of other usb drivers do. ALSA returns > > POLLERR | POLLNVAL, by the way, which I think is a poor choice. > > Indeed, POLLNVAL has a clear semantics that doesn't apply here.
In fact, POLLNVAL is currently only set by ./sound/core/init.c and by ./drivers/media/video/zoran/zoran_driver.c. In both cases it's rather dubious. > > This doesn't really seem to be standardized :-( > > CC'ing LKML with the question. > > POLLERR | POLLHUP and POLLERR won't make a difference to select(), but we > should still standardize on a poll() return code when devices are > unregistered > and/or - for hot-pluggable devices - disconnected (for V4L devices > unregistered usually means disconnected) ? Drivers return POLLERR, POLLERR|POLLHUP or POLLHUP in case of a disconnect. I'm leaning towards POLLHUP as the most appropriate poll return value for a USB disconnect. Regards, Hans -- Hans Verkuil - video4linux developer - sponsored by Cisco -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html