[Openvortex-dev] Eureka!

[Shamus]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Hi all!

I've finally figured out what the heck is causing the kernel
panic--and quite frankly, I'm having a hard time figuring out just how
the driver *works* for you guys who it works for!

Let me explain...

The problem lies in this line (from vortex_interrupt()):

    snd_mpu401_uart_interrupt(vortex->irq,
vortex->rmidi->private_data, regs);

Putting a printk in front of this line verifies that vortex->rmidi is
NULL! So of course the machine crashes when trying to dereference
private_data...

I believe the root of the problem is in au88x0_mpu401.c:

int __devinit snd_vortex_midi(vortex_t *vortex)
{
  snd_rawmidi_t *rmidi;
  int temp, mode;
  mpu401_t *mpu;
  int port;

... snipped ...

  if ((temp = snd_mpu401_uart_new(vortex->card, 0, MPU401_HW_AUREAL,
port, 1, 0, 0, &rmidi)) != 0)

... snipped ...

  mpu = snd_magic_cast(mpu401_t, rmidi->private_data, return -ENOMEM);
  mpu->cport = (unsigned long)(vortex->mmio + (VORTEX_MIDI_CMD >> 2));
#endif
  return 0;
}

Here rmidi is declared a local variable to the function, which means
after you initialize rmidi in the snd_mpu_401_uart_new() function, by
the end of snd_vortex_midi() the local variable is thrown away! The
same goes for the variable mpu at the very end--it's initialized and
then thrown away...

I can't seem to find any other place that vortex->rmidi gets
initialized, so how come it works for you guys? It should, by all
rights, crash and burn on you. If not, then how does vortex->rmidi
(from vortex_interrupt()) get initialized?

Shouldn't the code in snd_vortex_midi() be something along the lines
of

  if ((temp = snd_mpu401_uart_new(vortex->card, 0, MPU401_HW_AUREAL,
port, 1, 0, 0, &vortex->rmidi)) != 0)

? Am I missing something?

- -- Shamus

-----BEGIN PGP SIGNATURE-----
Version: Encrypted with PGP Plugin for Calypso

iQA/AwUBPqjdiphOW/ztyY5GEQIjjwCfeYH9O8LUzc9CgnaJuUQpYQuGocAAoIoK
H/lANVpk4P+9Q7+snUCHCrRI
=Rc+0
-----END PGP SIGNATURE-----