linux-kernel - Re: SB16 build error.

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Message-ID: <s5hy60jwocc.wl%tiwai@suse.de>
Date:	Thu, 30 Jun 2011 13:28:03 +0200
From:	Takashi Iwai <tiwai@...e.de>
To:	Ralf Baechle <ralf@...ux-mips.org>
Cc:	Jaroslav Kysela <perex@...ex.cz>, alsa-devel@...a-project.org,
	linux-kernel@...r.kernel.org, linux-mips@...ux-mips.org,
	florian@...ux-mips.org, Florian Fainelli <florian@...nwrt.org>,
	linux-arch@...r.kernel.org, Richard Henderson <rth@...ddle.net>,
	Ivan Kokshaysky <ink@...assic.park.msu.ru>,
	Matt Turner <mattst88@...il.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>,
	"David S. Miller" <davem@...emloft.net>, sparclinux@...r.kernel.org
Subject: Re: SB16 build error.

At Thu, 30 Jun 2011 13:05:54 +0200,
Takashi Iwai wrote:
> 
> At Thu, 30 Jun 2011 11:52:54 +0100,
> Ralf Baechle wrote:
> > 
> > On Thu, Jun 30, 2011 at 12:15:56PM +0200, Takashi Iwai wrote:
> > 
> > > At Thu, 30 Jun 2011 10:17:54 +0100,
> > > Ralf Baechle wrote:
> > > > 
> > > > Found on a MIPS build but certain other architectures will have the same
> > > > issue:
> > > > 
> > > >   CC      sound/isa/sb/sb16_csp.o
> > > > sound/isa/sb/sb16_csp.c: In function ‘snd_sb_csp_ioctl’:
> > > > sound/isa/sb/sb16_csp.c:228: error: case label does not reduce to an integer constant
> > > > make[1]: *** [sound/isa/sb/sb16_csp.o] Error 1
> > > > make: *** [sound/isa/sb/sb16_csp.o] Error 2
> > > > 
> > > > This error message is caused by the _IOC_TYPECHECK() error check triggering
> > > > due to excessive ioctl size on Alpha, PowerPC, MIPS and SPARC which define
> > > > _IOC_SIZEBITS as 13.  On all other architectures define it as 14 so struct
> > > > snd_sb_csp_microcode with it's little over 12kB will just about fit into
> > > > the 16kB limit.
> > > 
> > > What about the patch below?
> > 
> > I have no idea how big the soundblaster microcode being loaded actually is,
> > that is if the reduced size of 0x1f00 will be sufficient.
> 
> The files found in /lib/firmware/sb16 are all under 2kB, thus likely
> sufficient.

Too shortly answered.  It turned out that some CSP codes (like Qsound)
can be above that size, it's almost 12kB.  So the size in the original
code is really the necessary requirement, and the patch breaks for
such a case.

An ugly workaround would be to fake the ioctl size.  But this is
certainly to be avoided, since it has been broken on the specific
platforms for ages, thus breaking for them would be mostly harmless,
too.

> > Aside of that I
> > don't see a problem - I don't see how the old ioctl can possibly have been
> > used before so there isn't a compatibility problem.
> > 
> > Or you could entirely sidestep the problem and use request_firmware() but
> > I guess that's more effort than you want to invest.
> 
> Yeah, that's another option I thought of.  But it's too intrusive for
> 3.0-rc6, so I'd like waive it for 3.1.

Actually the request_firmware() was implemented for some auto-loadable
CSP codes.  Others need the manual loading, so it is via ioctl.  It
can be converted, but I don't think it makes sense for such old
stuff.  After all, it still works with x86-ISA as is.


thanks,

Takashi
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