At Tue, 11 Nov 2008 11:57:29 +0100, Jelle de Jong wrote:
Takashi Iwai wrote:
At Tue, 11 Nov 2008 10:43:00 +0100, Jelle de Jong wrote:
Takashi Iwai wrote:
At Sun, 09 Nov 2008 15:59:03 +0100, Jelle de Jong wrote:
Hello everybody,
I am trying to use udev to get fixed device names depending on the location of the device on the usb bus. The udev rules seems to be working fine, however i cant get dmix to work with the udev rules using only hw dies work. If i remove the udev rules the dmixer works fine.
Can somebody look at the attachment, and maybe do some testing, i would highly appreciate it.
Swapping the card numbers with udev might have a problem because the driver itself remembers the card index, and this number isn't swapped -- thus you get inconsistency between the device file and the internal index number.
BTW, if you just would like to keep the fixed device index for a certain usb device path, try my old patch below. It adds devpath option to snd-usb-audio, and you can specify the usb device path string ("usb-$BUSNAME-$DEVPATH").
Takashi
Thank you Takashi for thanking the time to answer the question. I don't understand. If udev created the card numbers in the first place, swapping them should not make a difference?
udev just renames a file. But, the index number is stored in the driver itself, and it can be read via an API function.
and why does the audio work fine with only hw:x and not when using dmix:x.
Unless you change the device file name, it works. Or, use an id string instead of an index number. The id string is found in /proc/asound/cards as [xxx]. Or, you can simply set up the slots option of snd module or set up the index option of each module. See ALSA-Configuration.txt.
How is the internal index number created?
Either via a module / kernel boot option, or created dynamically via the driver.
Can I control this index with udev? did I forget something in my udev rules?
No. As mentioned, your udev rule just renames the file.
Custom compiling sound modules is no option, it will break maintainability of the system in every way, sorry for this not being an sustainable option.
IMO, changing udev rule could be more fragile than a custom module...
Almost all devices can be managed with udev rules, that is where the system is designed for, there are also alsa rules in there, if they don't work what is wrong then? is it an alsa issue, or udev, what are the dependencies when alsa uses hardware. How are the /dev/snd/* devices used and what is the /proc/asound/* for ?
The card index mechanism in ALSA was introduced much before udev was born. It's just a legacy mechanism, but it's hard to kill without breaking the running system, unfortunately.
Takashi
When reading the explanations I understand that we are kind of dealing with a legacy issue. Is it possible to add some features to alsa to still get what I need to be able to always use a fixed usb port for audio for one user. For example if i take the content of ../cards it is capable of showing the usb path. If I can use this in my .asoundrc all problems go away, and no need for udev rules to rename devices. This same system is used input devices for Xorg with /dev/input/by-path/
Yeah, it's worth to add a new identification way via a system path. It'll be an extention and cannot work as is now, though :)
In your case, try to pass "default", "default_1" or "default_2" to card id instead of index number.
For example, the below should work without an extra ~/.asoundrc
% aplay -Dplug:dmix:default foo.wav
Takashi
cat /proc/asound/cards
0 [Intel ]: HDA-Intel - HDA Intel HDA Intel at 0xf7db8000 irq 16 1 [pcsp ]: PC-Speaker - pcsp Internal PC-Speaker at port 0x61 2 [Em28xx Audio ]: Empia Em28xx AudEm28xx Audio - Em28xx Audio Empia Em28xx Audio 3 [default ]: USB-Audio - USB AUDIO USB AUDIO at usb-0000:00:1d.7-4.1, full speed 4 [default_1 ]: USB-Audio - USB AUDIO USB AUDIO at usb-0000:00:1d.7-4.2, full speed 5 [default_2 ]: USB-Audio - USB AUDIO USB AUDIO at usb-0000:00:1d.7-4.3, full speed 6 [default_3 ]: USB-Audio - USB AUDIO USB AUDIO at usb-0000:00:1d.7-4.4, full speed
Would it be possible to create something like the below:
echo 'pcm.!default { type plug slave.pcm dmixer } pcm.dmixer { type dmix ipc_key 1024 slave.pcm hw:path:usb-0000:00:1d.7-4.1 } ctl.dmixer { type hw card path:usb-0000:00:1d.7-4.1 } pcm.dsp { type plug slave.pcm dmixer } ctl.mixer { type hw card path:usb-0000:00:1d.7-4.1 }' | tee /home/user0/.asoundrc chmod 600 /home/user0/.asoundrc chown user0:user0 /home/user0/.asoundrc
Thanks in advance,
Jelle