> -----Original Message----- > From: Takashi Iwai [mailto:tiwai@xxxxxxx] > Sent: Friday, October 23, 2015 4:44 PM > > 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. Okay. So the target is trying to assure a monitor uses the same PCM device statically as long as it's physically connected, over display mode change and power cycle. And your and David's scheme to add 2 extra PCM devices in the reserved area should assure this for common configurations on Intel platforms, usually at most 1 DP + 1 HDMI. We can check the length of device entries for a pin and add (Len -1) PCM devices. This can also work for Nvidia & AMD. Thanks again for your clarification. Regards Mengdong _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
