--- On Tue, 24/5/11, Devin Heitmueller <dheitmueller@xxxxxxxxxxxxxx> wrote: > From: Devin Heitmueller <dheitmueller@xxxxxxxxxxxxxx> > Subject: Re: [ANNOUNCE] experimental alsa stream support at xawtv3 > To: "Hans Verkuil" <hverkuil@xxxxxxxxx> > Cc: "Mauro Carvalho Chehab" <mchehab@xxxxxxxxxx>, "Linux Media Mailing List" <linux-media@xxxxxxxxxxxxxxx> > Date: Tuesday, 24 May, 2011, 16:57 > On Tue, May 24, 2011 at 2:50 AM, Hans > > Oh, and how is it expected to handle informing the > application about > device contention between DVB and V4L? Some devices > share the tuner > and therefore you cannot use both the V4L and DVB device at > the same > time. Other products have two independent input paths > on the same > board, allowing both to be used simultaneously (the > HVR-1600 is a > popular example of this). Sysfs isn't going to tell > you this > information, which is why in the MC API we explicitly added > the notion > of device groups (so the driver author can explicitly state > the > relationships). > > Today MythTV users accomplish this by manually specifying > "Input > Groups". I say that's what they do, but in reality > they don't realize > that they need to configure MythTV this way until they > complain that > MythTV recordings fail when trying to record programs on > both inputs, > at which point an advanced user points it out to > them. End users > shouldn't have to understand the internal architecture of > their > capture card just to avoid weird crashy behavior (which is > what often > happens if you try to use both devices simultaneously since > almost no > hybrid drivers do proper locking). Are there mechanisms for device-locking in the v4l api? With my 2 hybrid saa7134 cards I have observed exactly this issues in Mythtv and also in xawtv and kaffeine.... At the moment I disable one device via additional card definitions and modprobe-parameters, so that the other one is "alone" and only one app gets control over the tuner. But this driver (saa7134) seams not even lock the /dev/video0 correctly, as starting xawtv twice renders the card inoperable and forces rebooting to get the card working again... Is there a good starting point to implement the locking? > I am in favor of this finally getting some attention, but > the reality > is that sysfs isn't going to cut it. It just doesn't > expose enough > information about the underlying hardware layout. > > Devin > > -- > Devin J. Heitmueller - Kernel Labs > http://www.kernellabs.com > -- > 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 > Emil -- 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
