linux-kernel - Re: [PATCH] mips/ad1843: convert time to jiffies HZ independent

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Date:	Sun, 14 Jun 2015 19:16:59 +0200
From:	Nicholas Mc Guire <der.herr@...r.at>
To:	Takashi Iwai <tiwai@...e.de>
Cc:	Nicholas Mc Guire <hofrat@...dl.org>,
	Jaroslav Kysela <perex@...ex.cz>, alsa-devel@...a-project.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mips/ad1843: convert time to jiffies HZ independent

On Sun, 14 Jun 2015, Takashi Iwai wrote:

> At Sun, 14 Jun 2015 10:20:59 +0200,
> Nicholas Mc Guire wrote:
> > 
> > PI compliance scanning with coccinelle flagged:
> > ./sound/mips/ad1843.c:503:2-32: WARNING: 
> > 	timeout (5) seems HZ dependent
> > 
> > This was introduced in 'commit 862c2c0a61c5 ("ALSA: ALSA driver for SGI O2
> > audio board")'. schedule_timeout_interruptible() expects a timeout in
> > jiffies so the numeric constant makes the effective timeout HZ dependent.
> > Simply put it through msecs_to_jiffies() to make it HZ independent.
> > 
> > Signed-off-by: Nicholas Mc Guire <hofrat@...dl.org>
> > ---
> > 
> > The loop here is bounded by 500 jiffies and it does not seem reasonable that
> > it would loop 10 times faster on HZ=1000 configs over HZ=100 configs. The
> > conversion via msecs_to_jiffies(5) ensures that it will loop at most 100
> > times for all configs of HZ which seems reasonable (to me) but needs to be
> > checked by someone that knows the details of this driver. 
> 
> Using 5ms looks reasonable for this case.  However,
> schedule_timeout_interruptible() isn't.  This is a loop that won't
> break.  So, the best would be to replace it with msleep() or its
> friends.
> 
> > Note that the CONFIG_SND_PCM_OSS dependency was not listed in the 
> > Depends on: in Kconfig (which it probably should)
> 
> Why at all?  It has nothing to do with OSS.
>
the procedure to see the problem I used was
(linux-next 20150612)
make ip32_defconfig ARCH=mips
make menuconfig ARCH=mips
  Device Drivers
    ...
    <M> Sound card support  --->
        <M>   Advanced Linux Sound Architecture  --->
            [*]   MIPS sound devices  --->
                  <M>   SGI O2 Audio

compiling fails with:
  MODPOST 95 modules
ERROR: "snd_pcm_period_elapsed" [sound/mips/snd-sgi-o2.ko] undefined!
ERROR: "snd_pcm_set_ops" [sound/mips/snd-sgi-o2.ko] undefined!
ERROR: "snd_pcm_lib_get_vmalloc_page" [sound/mips/snd-sgi-o2.ko] undefined!
ERROR: "snd_pcm_lib_ioctl" [sound/mips/snd-sgi-o2.ko] undefined!
ERROR: "_snd_pcm_lib_alloc_vmalloc_buffer" [sound/mips/snd-sgi-o2.ko] undefined!
ERROR: "snd_pcm_new" [sound/mips/snd-sgi-o2.ko] undefined!
ERROR: "snd_pcm_lib_free_vmalloc_buffer" [sound/mips/snd-sgi-o2.ko] undefined!
make[1]: *** [__modpost] Error 1
make: *** [modules] Error 2

as the pcm_lib functions depend on SND_PCM I added that - So
if I add the below patch the problem goes away and the module 
build correclty - not saying that this is the right fix though
(did not look into it in more detail yet)

>From d9cb7d166613e6129f021a913f66f377f5ac56c0 Mon Sep 17 00:00:00 2001
From: Nicholas Mc Guire <hofrat@...dl.org>
Date: Sun, 14 Jun 2015 19:06:19 +0200
Subject: [PATCH] ALSA: let SND_SGI_O2 select SND_PCM

Signed-off-by: Nicholas Mc Guire <hofrat@...dl.org>
---
 sound/mips/Kconfig |    1 +
 1 file changed, 1 insertion(+)

diff --git a/sound/mips/Kconfig b/sound/mips/Kconfig
index d2f615a..7875af0 100644
--- a/sound/mips/Kconfig
+++ b/sound/mips/Kconfig
@@ -12,6 +12,7 @@ if SND_MIPS
 config SND_SGI_O2
 	tristate "SGI O2 Audio"
 	depends on SGI_IP32
+	select SND_PCM
         help
                 Sound support for the SGI O2 Workstation. 
 
-- 
1.7.10.4

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