[alsa-devel] Userspace control of HDA port connections

[Takashi Iwai]

At Thu, 20 Dec 2007 16:45:09 -0500,
Andrew Paprocki wrote:
> 
> Takashi,
> 
> I'm wondering if there is any interest in providing a userspace way of
> modifying the HDA port/mixer input/output mappings? The driver
> currently uses hard-coded models to define the standard configuration
> for a given piece of hardware, but this doesn't allow a user to
> redefine a line-in port as an output port if the chipset has an
> available unmapped mixer. I'm bringing this up because from what I
> understand of the ALC883 is that it has 4 mixers, yet on my
> motherboard there are only 3 ports configured as output by default
> (6stack-dig). Correct me if I'm wrong, but I should be able to map all
> of the physical jacks as outputs and then assign each of the mixers to
> a jack or more than one jack. That would require adding a new model to
> the driver and/or unloading/reloading the module with a new model
> string. In a system which has the driver built-in and isn't using
> modules, this requires a reboot. If there was a userspace way of
> reconfiguring the jacks (via /proc/asound?) then perhaps even all of
> the hardware -> model mappings could be moved into a little tool run
> at boot time which doesn't require a kernel change every time new
> hardware is introduced. A nice little ncurses tool could even be made
> to modify port mappings. What do you think? If I'm misunderstanding
> the capabilities of the chips please let me know.

It's not possible right now as is.

I've once created a user-space setup tool for hda driver, but it was
only for older versions and very unlikely works with the current
version.  You can find it at:

	ftp://ftp.suse.com/pub/people/tiwai/hda-tools/

I think the idea itself is OK, but the implementation must be more
improved.  The data transfer of variable length data via ioctl is
basically a bad idea, and this could be better in a simple read/write
stream.  Also, the creation of mixer elements has some issues to
reconsider.

> Thanks,
> -Andrew
> 
> p.s. I still have yet to test out the multi-card patch. I'll reply to
> that once I have more info.

Yeah, let me know if it works.  I think this should be merged to the
upstream soon.


Takashi