Re: [PATCH] Fix Alsa issues including Oopses with OSS emulation

[Benjamin Herrenschmidt <benh@kernel.crashing.org>]

On Wed, 2004-12-22 at 19:13 +0100, Benjamin Herrenschmidt wrote:
> This patch (which will be send upstream separately by the Alsa folks) fixes
> an signed vs. unsigned char problem in Alsa which was the cause of the Oops
> people were experiencing on ppc with OSS emulation and possibly other issues.

Ok, actually, the one that will be commited upstream is a bit different,
here it is:


Summary: [ALSA] Fix the wrong sign of format data entries

Fix suggested by Benjamin Herrenschmidt <benh@kernel.crashing.org>

On architectures like PPC, char is handled as "unsigned char", thus the
pcm_format_data table entries with -1 give a positive 255.  This causes
Oops with OSS-emulation on such architectures.

The patch simply adds the right signed/unsigned prefix to fix this problem.


Signed-off-by: Takashi Iwai <tiwai@suse.de>


--- linux/sound/core/pcm_misc.c 8 Jun 2004 16:57:28 -0000       1.12
+++ linux/sound/core/pcm_misc.c 22 Dec 2004 18:07:29 -0000      1.14
@@ -25,11 +25,14 @@
 #include <sound/pcm.h>
 #define SND_PCM_FORMAT_UNKNOWN (-1)
 
+/* NOTE: "signed" prefix must be given below since the default char is
+ *       unsigned on some architectures!
+ */
 struct pcm_format_data {
-       char width;     /* bit width */
-       char phys;      /* physical bit width */
-       char le;        /* 0 = big-endian, 1 = little-endian, -1 = others */
-       char signd;     /* 0 = unsigned, 1 = signed, -1 = others */
+       unsigned char width;    /* bit width */
+       unsigned char phys;     /* physical bit width */
+       signed char le; /* 0 = big-endian, 1 = little-endian, -1 = others */
+       signed char signd;      /* 0 = unsigned, 1 = signed, -1 = others */
        unsigned char silence[8];       /* silence data to fill */
 };