linux-kernel - Re: [PATCH] ALSA: patch_realtek: handle unset external amp bits

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Message-ID: <s5h8w0gskds.wl%tiwai@suse.de>
Date:	Fri, 26 Nov 2010 06:51:11 +0100
From:	Takashi Iwai <tiwai@...e.de>
To:	Kyle McMartin <kyle@...artin.ca>
Cc:	alsa-devel@...a-project.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ALSA: patch_realtek: handle unset external amp bits

At Thu, 25 Nov 2010 13:57:30 -0500,
Kyle McMartin wrote:
> 
> From: Kyle McMartin <kyle@...hat.com>
> 
> Commit ef5dbbcc removes the default initialization of init_amp to
> ALC_INIT_DEFAULT, with the justification that it should be set by
> alc_subsystem_id, which contains a switch case:
> 
>         tmp = (ass & 0x38) >> 3;        /* external Amp control */
>         switch (tmp) {
>         case 1:
> 	...
> 	case 5:
> 	}
> 
> Which handles values 1,3,7 for GPIOs, or 5 to set _DEFAULT.
> 
> But... what if it's 0? :)
> 
> I got a bug report this morning from a user whose sound had broken
> between 2.6.34 and 2.6.35, and I bisected it down to this commit.
> 
> [ 32.366183] ALSA sound/pci/hda/patch_realtek.c:1374: realtek: Enabling
> init ASM_ID=0x8a05 CODEC_ID=10ec0888
> 
> (0x8a05 & 0x38) >> 3 = 0;
> 
> But otherwise the SKU looks fine (since if I revert that commit, it
> seems to work correctly.)
> 
> I think the best thing to do would be to either restore the 'redundant'
> default initialization, or quirk it.
> 
> https://bugzilla.redhat.com/show_bug.cgi?id=657388
> 
> Signed-off-by: Kyle McMartin <kyle@...hat.com>

How about setting default to ALC_INIT_DEFAULT instead like the patch
below?  This is safer than forcing ALC_INIT_DEFAULT to all, I
suppose.


thanks,

Takashi

---
diff --git a/sound/pci/hda/patch_realtek.c b/sound/pci/hda/patch_realtek.c
index 81a2a49..886d7c7 100644
--- a/sound/pci/hda/patch_realtek.c
+++ b/sound/pci/hda/patch_realtek.c
@@ -1614,6 +1614,7 @@ do_sku:
 		spec->init_amp = ALC_INIT_GPIO3;
 		break;
 	case 5:
+	default:
 		spec->init_amp = ALC_INIT_DEFAULT;
 		break;
 	}
--
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