On Fri, 23 Oct 2015 10:35:26 +0200, Lin, Mengdong wrote: > > > -----Original Message----- > > From: Takashi Iwai [mailto:tiwai@xxxxxxx] > > Sent: Friday, October 23, 2015 1:54 PM > > > > On Fri, 23 Oct 2015 07:30:12 +0200, > > Lin, Mengdong wrote: > > > > > > > -----Original Message----- > > > > From: David Henningsson [mailto:david.henningsson@xxxxxxxxxxxxx] > > > > Sent: Thursday, October 22, 2015 4:53 PM > > > > > > [snip] > > > > > > > I'll try to explain my suggestion (which I believe Takashi's buying > > > > too) one more time then: > > > > > > > > First, when a monitor is plugged in, we need to dynamically assign > > > > this monitor to five PCM devices. I believe this scheme will be best: > > > > > > > > For a monitor at pin nid 0x05, dev index 0, it will prefer PCM 3. > > > > For a monitor at pin nid 0x06, dev index 0, it will prefer PCM 7. > > > > For a monitor at pin nid 0x07, dev index 0, it will prefer PCM 8. > > > > For a monitor at dev index 1 (any pin), it will prefer PCM 9. > > > > For a monitor at dev index 2 (any pin), it will prefer PCM 10. > > > > > > > > For monitors at dev indices > 2 (can that happen?), or if the PCM is > > > > already assigned to something else, try PCMs in this order: 9, 10, 3, 7, 8. > > > > (Subject to discussion perhaps, I don't think the order matters too > > > > much, because conflicts will be rare in practice.) > > > > > > Hi David, > > > > > > Would you please clarify why PA needs such a fixed binding between PCM > > 3,7, 8 and pin 0x05,6,7? > > > > It's not PA's requirement. The only concern here is for people who uses > > ALSA device directly, e.g. via aplay -Dhdmi:2. The first monitor is > > guaranteed to be mapped to the compatible position for such people. > > Excuse me, could you share more background info here? > Even before DP MST support, it seems that such people need to know what pin is used to connect a monitor. Why? On the existing machines, if you connect to a certain DP port, it's always assigned to the same device. This is guaranteed, so it's perfectly fine to use this device statically for your purpose. > The user can enumerate the PCM devices, and the PCM's jack ioctl can show whether a monitor is available behind this PCM device, no matter the driver uses fixed or dynamic binding between the PCM and pins. > So people can always choose a PCM to use a monitor. I feel they need not care which pin is used for the monitor. People *can* choose, but it doesn't mean people *must* reselect another number out of sudden. If they have to, it may be called a regression. Takashi _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
