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

[Luigi Rizzo]

as you can imagine i have lost memory on whay i made this
particular change. It might have something to do with supporting
newer SB clones or something similar, dont know

cheers
luigi

On Tue, Oct 26, 2004 at 12:44:33AM +0200, Bartosz Fabianowski wrote:
> [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