[Qemu-devel] A question regarding your FreeBSD sound driver

[Bartosz Fabianowski]

[Sent to Luigi, CC to Qemu-devel]

Hi,

I have a short question about a piece of code that you wrote some six 
years ago. I realize the chances you still know the code well enough to 
answer it are slim, but I hope you don't mind me asking anyway. While 
working on the Qemu system emulator, a developer noticed that the code 
FreeBSD uses to reset the SB16 sound card differs in one detail from 
what other systems do.

The detail is that to begin a DSP reset, most drivers set the value of 
the appropriate I/O port to 1. FreeBSD, however, sets the value to 3. 
Looking through the FreeBSD CVS commit log, I noticed that up until 
version 1.6 of sb16.c, FreeBSD also used a value of 1.

At that point, however, a change made by you was committed that changed 
this:

outb(io_base + SBDSP_RST, 1);

To this:

outb(io_base + SBDSP_RST, 3);

There is no explanation in the commit log for why you changed the value. 
So, my question is, do you by any chance still have the documentation 
that prompted you to use the value of 3 instead of 1? This change was 
made in 1998 and you probably haven't looked at the code since then. But 
then again, maybe you still have the reference that made you change this 
at hand.

Thanks in advance for any insight you may provide.

Regards,
- Bartosz Fabianowski