On 5/8/24 19:10, Wesley Cheng wrote: > Hi Pierre, > > On 5/7/2024 2:26 PM, Pierre-Louis Bossart wrote: >> >> >> On 5/7/24 14:51, Wesley Cheng wrote: >>> Add SND kcontrol to SOC USB, which will allow for userpsace to determine >>> which USB card number and PCM device to offload. This allows for >>> userspace >>> to potentially tag an alternate path for a specific USB SND card and PCM >>> device. Previously, control was absent, and the offload path would be >>> enabled on the last USB SND device which was connected. This logic will >>> continue to be applicable if no mixer input is received for specific >>> device >>> selection. >>> >>> An example to configure the offload device using tinymix: >>> tinymix -D 0 set 'USB Offload Playback Route Select' 1 0 >>> >>> The above command will configure the offload path to utilize card#1 >>> and PCM >>> stream#0. >> >> I don't know how this is usable in practice. Using card indices is >> really hard to do, it depends on the order in which devices are >> plugged-in... > > How are the existing mechanisms handling USB audio devices, or what is > the identifier being used? Well it's a mess, that's why I asked. There are configuration work-arounds to make sure that 'local' accessories are handled first and get repeatable card indices. But between USB devices I guess the rule is 'anything goes'. Even if there are two devices connected at boot, the index allocation will depend on probe order. The card names are not necessarily super-useful either, i.e. yesterday I was confused by an USB card named "CODEC" without any details.
