NetBSD Problem Report #55175

From nia@netbsd.org  Tue Apr 14 12:06:36 2020
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Date: Tue, 14 Apr 2020 12:06:36 +0000
From: nia <nia@NetBSD.org>
To: gnats-bugs@netbsd.org
Subject: Interpretation of AUDIO_FORMAT_LINEAR is wrong for 8-bit samples

>Number:         55175
>Category:       kern
>Synopsis:       Interpreation of AUDIO_FORMAT_LINEAR is wrong for 8-bit samples
>Confidential:   no
>Severity:       non-critical
>Priority:       medium
>Responsible:    nia
>State:          closed
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Tue Apr 14 12:10:00 +0000 2020
>Closed-Date:    Thu Aug 20 08:00:22 +0000 2020
>Last-Modified:  Thu Aug 20 08:00:22 +0000 2020
>Originator:     nia <nia@NetBSD.org>
>Release:        NetBSD 9.0_STABLE
>Organization:
>Environment:
System: NetBSD r 9.0_STABLE NetBSD 9.0_STABLE (GENERIC) #13: Mon Apr 13 15:12:50 IST 2020 nia@r:/home/nia/netbsd-9/sys/arch/amd64/compile/obj/GENERIC amd64
Architecture: x86_64
Machine: amd64
>Description:
illumos/Solaris/SunOS define AUDIO_ENCODING_LINEAR as follows:

#define AUDIO_ENCODING_LINEAR (3) /* Signed Linear PCM encoding */

However, in NetBSD, it's an alias for AUDIO_ENCODING_PCM16, which is deprecated.

#define AUDIO_ENCODING_PCM16            3 /* signed linear PCM, obsolete */
#define AUDIO_ENCODING_LINEAR           AUDIO_ENCODING_PCM16 /* SunOS compat */

Note that both definitions say the encoding is signed...

In the kernel, PCM16 is interpreted as unsigned if the samples are 8-bit. This seems unexpected and wrong.

I'm not sure of the origin of the definition of PCM16 and as far as I can tell it was never documented in NetBSD, but far more code in the wild uses LINEAR, and even our own headers say it's signed.
>How-To-Repeat:
Attempt to do audio I/O with precision=8 and AUDIO_FORMAT_LINEAR.
>Fix:
Probably this:

Index: audio.c
===================================================================
RCS file: /cvsroot/src/sys/dev/audio/audio.c,v
retrieving revision 1.65
diff -u -r1.65 audio.c
--- audio.c	26 Mar 2020 13:32:03 -0000	1.65
+++ audio.c	14 Apr 2020 11:35:13 -0000
@@ -6086,12 +6086,8 @@
 {

 	/* Convert obsoleted AUDIO_ENCODING_PCM* */
-	/* XXX Is this conversion right? */
 	if (p->encoding == AUDIO_ENCODING_PCM16) {
-		if (p->precision == 8)
-			p->encoding = AUDIO_ENCODING_ULINEAR;
-		else
-			p->encoding = AUDIO_ENCODING_SLINEAR;
+		p->encoding = AUDIO_ENCODING_SLINEAR;
 	} else if (p->encoding == AUDIO_ENCODING_PCM8) {
 		if (p->precision == 8)
 			p->encoding = AUDIO_ENCODING_ULINEAR;

>Release-Note:

>Audit-Trail:

Responsible-Changed-From-To: kern-bug-people->isaki
Responsible-Changed-By: isaki@NetBSD.org
Responsible-Changed-When: Thu, 16 Apr 2020 13:10:45 +0000
Responsible-Changed-Why:
I take it.


From: "Nia Alarie" <nia@netbsd.org>
To: gnats-bugs@gnats.NetBSD.org
Cc: 
Subject: PR/55175 CVS commit: src/sys/dev/audio
Date: Tue, 26 May 2020 10:12:12 +0000

 Module Name:	src
 Committed By:	nia
 Date:		Tue May 26 10:12:12 UTC 2020

 Modified Files:
 	src/sys/dev/audio: audio.c

 Log Message:
 audio: Restore compat with Solaris for 8-bit LINEAR.

 It's always signed, unless it's LINEAR8.

 PR kern/55175


 To generate a diff of this commit:
 cvs rdiff -u -r1.71 -r1.72 src/sys/dev/audio/audio.c

 Please note that diffs are not public domain; they are subject to the
 copyright notices on the relevant files.

From: Tetsuya Isaki <isaki@pastel-flower.jp>
To: gnats-bugs@netbsd.org
Cc: gnats-admin@netbsd.org,
	netbsd-bugs@netbsd.org,
	nia <nia@NetBSD.org>
Subject: Re: PR/55175 CVS commit: src/sys/dev/audio
Date: Fri, 29 May 2020 12:26:29 +0900

 At Tue, 26 May 2020 10:15:01 +0000 (UTC),
 Nia Alarie wrote:
 >  Module Name:	src
 >  Committed By:	nia
 >  Date:		Tue May 26 10:12:12 UTC 2020
 >  
 >  Modified Files:
 >  	src/sys/dev/audio: audio.c
 >  
 >  Log Message:
 >  audio: Restore compat with Solaris for 8-bit LINEAR.
 >  
 >  It's always signed, unless it's LINEAR8.

 This might restore compatibility with Sun but
 it breaks compatibility with recent 20+ years NetBSD binary.
 I'm not sure which is better.
 But anyway, it's too trivial case.  I have no futher opinions.

 Thanks,
 ---
 Tetsuya Isaki <isaki@pastel-flower.jp / isaki@NetBSD.org>

Responsible-Changed-From-To: isaki->nia
Responsible-Changed-By: isaki@NetBSD.org
Responsible-Changed-When: Fri, 29 May 2020 03:32:24 +0000
Responsible-Changed-Why:
This is no longer mine.


State-Changed-From-To: open->closed
State-Changed-By: nia@NetBSD.org
State-Changed-When: Thu, 20 Aug 2020 08:00:22 +0000
State-Changed-Why:


>Unformatted:

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