On Tue, 12.05.09 08:09, Jaroslav Kysela (perex@xxxxxxxx) wrote: > > 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. Why? Please elaborate! The whole point of this patch is to allow users to write struff like hw:/dev/snd/by-path/pci-0000:00:1a.7-usb-0:2:1.2 whereever they could otherwise write hw:0. Why is that a bad 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. This is no improvement at all, because no application does that. The point of the patch was to improve the flexibility for all applications. Lennart -- Lennart Poettering Red Hat, Inc. lennart [at] poettering [dot] net http://0pointer.net/lennart/ GnuPG 0x1A015CC4 _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
