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To: Doug Rabson <dfr@freebsd.org>
Cc: cvs-committers@freebsd.org, cvs-all@freebsd.org,
	yokota@zodiac.mech.utsunomiya-u.ac.jp
Subject: Re: cvs commit: src/sys/dev/acpica acpi.c 
In-reply-to: Your message of "Thu, 04 Oct 2001 01:31:17 MST."
             <200110040831.f948VHu13310@freefall.freebsd.org> 
References: <200110040831.f948VHu13310@freefall.freebsd.org> 
Date: Thu, 04 Oct 2001 20:59:37 +0900
From: Kazutaka YOKOTA <yokota@zodiac.mech.utsunomiya-u.ac.jp>
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>dfr         2001/10/04 01:31:17 PDT
>
>  Modified files:
>    sys/dev/acpica       acpi.c 
>  Log:
>  Check the compatible ID as well as the hardware ID in acpi_MatchHid.
>  
>  Revision  Changes    Path
>  1.41      +6 -1      src/sys/dev/acpica/acpi.c

I think we had better be careful when matching against compatible IDs.
We should distinguish the case when the hardware ID matches, and the
case when the compatible ID matches.

If we don't distinguish the hardware ID match and the compatible ID
match, the following will happen.

The device X has a hardware PnP ID of XXXYYYY and a compatible ID of
PNPWWWW.

The device driver A supports PNPWWWW device.

The device driver B supports XXXYYYY device.

When the driver A gets at the device X before the device B does, we
will have the driver A installed for this device, instead of the
driver B, which offers specific support for PNPWWWW.

We need to make the probe routine in the device drivers return 0
(exact match) when the hardware ID exactly matches, and return a
negative value (lower priority) when the compatible ID matches.

Kazu

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