ens1371/ac97 broken on my machine

[Cameron Hutchison <camh+alsa@xdna.net>]

The driver for the ens1371 chipset no longer works on my laptop.
It used to work in version 0.9.0rc3, but in version 0.9.2 and 0.93a, it
no longer works. When I try to run alsamixer, I get the error "No mixer
elems found"

Details:
  Distribution: Debian GNU/Linux (unstable)
  Kernel: Linux 2.4.19, 2.4.20, 2.4.21rc2
  Alsa kernel version: 0.9.2, 0.9.3a
  lspci output (with and without -n):
    00:09.0 Class 0401: 1102:8938
    00:09.0 Multimedia audio controller: Creative Labs ES1371

I've tracked the issue back to the AC97 codec where it creates the mixer
elements (in function snd_ac97_mixer(), file ac97_codec.c), in
particular, this piece of code:

        /* test for AC'97 */
        /* test if we can write to the record gain volume register */
        snd_ac97_write_cache(ac97, AC97_REC_GAIN, 0x8a06);
        if ((err = snd_ac97_read(ac97, AC97_REC_GAIN)) == 0x8a06) {
                ac97->scaps |= AC97_SCAP_AUDIO;
                ac97->caps = snd_ac97_read(ac97, AC97_RESET);
                ac97->ext_id = snd_ac97_read(ac97, AC97_EXTENDED_ID);
                if (ac97->ext_id == 0xffff)     /* invalid combination */
                        ac97->ext_id = 0;
        }

It seems that snd_ac97_read() does not read back the value 0x8a06 and
never sets AC97_SCAP_AUDIO, which means the mixer elements never get 
created.

I've successfully used this sound hardware with alsa for the last three
years.

Can anyone help?



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