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Subject: Re: SiS/Trident 4DWave sound driver oops
From: Robert Love <rml@tech9.net>
To: Tachino Nobuhiro <tachino@open.nm.fujitsu.co.jp>
Cc: "Michael F. Robbins" <compumike@compumike.com>,
        linux-kernel@vger.kernel.org
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On Thu, 2001-10-25 at 21:56, Tachino Nobuhiro wrote:
> Robert Love wrote:
> > Hm, I don't think so.  The last area is marked zero so code can know
> > when it ends.  This is common practice.
> 
> But the code does not use the last area. this is the code in
> ac97_probe_codec().

ARRAY_SIZE(x) returns the number of elements in x, but since everything
is 0-referenced going from 0 to i < ARRAY_SIZE isn't a problem.

ie int x[3];
ARRAY_SIZE(x) = 3;
but x[2] is last element... so no issue here.

> 	id1 = codec->codec_read(codec, AC97_VENDOR_ID1);
> 	id2 = codec->codec_read(codec, AC97_VENDOR_ID2);
> 	for (i = 0; i < ARRAY_SIZE(ac97_codec_ids); i++) {
> 		if (ac97_codec_ids[i].id == ((id1 << 16) | id2)) {
> 			codec->type = ac97_codec_ids[i].id;
> 			codec->name = ac97_codec_ids[i].name;
> 			codec->codec_ops = ac97_codec_ids[i].ops;
> 			break;
> 		}
> 	}
>   
> If id1 and id2 happen to be 0, it matches the last entry and codec_ops
> is set to uncertain value(maybe 0). it may cause the oops in ac97_init_mixer().

	Robert Love

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