Re: Re: snd_mpu401_uart: hang when trying to play .mid

[Takashi Iwai <tiwai@suse.de>]

At Mon, 06 Sep 2004 16:18:25 -0400,
Lee Revell wrote:
> 
> On Mon, 2004-09-06 at 14:58, Domen Puncer wrote:
> > On 06/09/04 18:25 +0200, Takashi Iwai wrote:
> > > At Mon, 6 Sep 2004 17:48:19 +0200,
> > > Domen Puncer wrote: 
> > > > On 06/09/04 17:18 +0200, Takashi Iwai wrote:
> > > > > At Sun, 5 Sep 2004 11:22:35 +0200,
> > > > > Domen Puncer wrote:
> > > > > Does your hardware really a MPU401 device?
> > > > 
> > > > I don't know, probably not.
> > > > 
> > > > > If not, you can remove the call of snd_mpu401_uart_new() in
> > > > > snd_trident_probe().
> > > > 
> > > > Or just never start kmid again :-)
> > > > My point is: user can hang the computer; this is a bug.
> > > 
> > > Sure.  Removing the unneeded creation of mpu401 interface is _the_
> > > solution if you really don't have mpu401.
> > 
> > Umm... you mean removing this for linus tree? Then why it was there
> > in the first place?
> 
> No, Takashi-san is telling you to try commenting this out and recompile
> and see if the problem goes away.  If so then we can figure out how to
> detect this MPU-less device and fix it in ALSA CVS.  He probably does
> not have access to the hardware to test it himself.

Exactly.  Thanks for interpretation ;)

> This is a pretty common issue with ALSA because a lot of cards that
> purport to be the same as another have small differences, and the alsa
> devs can't possibly test every single device.

Yes, indeed, the trident code is shared among several different chips
(trident 4D DX, 4D NX and SI7018), and MPU401 handling seems hitting
on SI7018 only.  I guess SI7018 is equipped mostly on laptops, which
unlikely have MPU401 connectors.  So, removing the mpu401 support for
SI7018 may be the simplest and safest solution.

Of course, we can track down the hang-up point (perhaps in the
interrupt handler, snd_mpu401_uart_interrupt()) and fix it, too.


Takashi


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