kern/100271: [acpi] [patch] acpi_video cant identify some Dell lcd's.

Bruno Ducrot bruno at
Mon Jul 17 14:50:25 UTC 2006

The following reply was made to PR kern/100271; it has been noted by GNATS.

From: Bruno Ducrot <bruno at>
To: bug-followup at, john at
Subject: Re: kern/100271: [acpi] [patch] acpi_video cant identify some Dell lcd's.
Date: Mon, 17 Jul 2006 16:40:22 +0200

 Looking :
 I think this part is problematic:
 +	display_index = adr & DOD_DEVID_MASK_DISPIDX;
 +	display_port = (adr & DOD_DEVID_MASK_DISPPORT) >> 4;
 +	if (!(adr & DOD_DEVID_SCHEME_STD)) {
 +		printf("Ignore non-standard device (%x).\n",
 +			adr & DOD_DEVID_MASK_FULL);
 +		return(NULL);
 +	}
 ACPI 2.0b reserve bits 30-31 to be 0, so if we follow exactly ACPI 3,
 that is if bit 31 is cleared then we can't be compatible with ACPI 2.0b.
 Therefore if we keep that if statement, we should at least verify that
 the DSDT is for ACPI 3.  Problem is : the DSDT header do have the
 same revision field for both specs 2.0b and 3.0.
 Worst, I've seen DSDT header with revision 1, even though they contains
 at least ACPI 2 objects (like processors, etc.)
 Sato-san, do you have any thought about this issue ?
 Bruno Ducrot
 --  Which is worse:  ignorance or apathy?
 --  Don't know.  Don't care.

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