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

From: Bartosz Fabianowski
Subject: [Qemu-devel] A question regarding your FreeBSD sound driver
Date: Tue, 26 Oct 2004 00:44:33 +0200
User-agent: Mozilla Thunderbird 0.8 (X11/20041018)

[Sent to Luigi, CC to Qemu-devel]


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.

- Bartosz Fabianowski

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