On Tue, 12 May 2009, Lennart Poettering wrote: > Heya! > > Traditionally low-level ALSA devices are opened with device strings like > 'hw:CARD' where CARD is either a numeric index or a card name. This > patch introduces a third syntax that allows you to specify the file name > of the control device node. The purpose for this is to make ALSA a bit > more like other Linux devices and allow implementaiton of udev device > symlinks similar to how disks are currently handled, with > /dev/disk/by-path/xxxx /dev/disk/by-id/xxxx and so on. > > With this patch this line: > > aplay -f CD -D hw:/dev/snd/controlC0 < /dev/urandom > > becomes equivalent to this line: > > aplay -f CD -D hw:0 < /dev/urandom > > A more useful example is this: > > aplay -f CD -D hw:/dev/snd/by-path/pci-0000:00:1a.7-usb-0:2:1.2 > > (this line requires a a few additional udev rules) > > This only works for control devices nodes, not for PCM or any other > device nodes. Since the control device node is used as 'entry point' > when opening PCM devices this is no limitation. NAK. Passing control device to open() functions is not a good idea. The snd_card_get_index() function might be extended to allow /dev style argument. Returned card index can be used as argument for hw: devices without this massive change. http://git.alsa-project.org/?p=alsa-lib.git;a=commit;h=33ab0b5381c87e151e87e5000964edd868484886 Jaroslav ----- Jaroslav Kysela <perex@xxxxxxxx> Linux Kernel Sound Maintainer ALSA Project, Red Hat, Inc. _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
