RE: [PATCH] ACPI: Adjust the return value of _REV on x86

From: Jason Ekstrand
Date: Sat Mar 14 2015 - 15:59:07 EST

From: Jason Ekstrand <jason@xxxxxxxxxxxxxx>

On Wed, 11 Mar 2015 22:50:47, Matthew Garrett <mjg59@xxxxxxxxxxxxx> wrote:
> The ACPI spec describes _REV as:
> "This predefined object evaluates to the revision of the ACPI Specification
> that the specified \_OS implements"
> We've been assuming that this should increment as ACPICA gains support for
> new versions of the spec. Unfortunately, Windows always reports "2" for this
> value and vendors are now using this as a means to tell whether a system is
> running Windows or Linux. From an HP Envy 15:
> If (LOr (LEqual (_REV, 0x03), LEqual (_REV, 0x05)))
> From a Dell XPS 13:
> If ((_REV == 0x05))

I can confirm that on my 2015 Dell XPS 13, this patch fixes both the audio
and suspend/resume. I'm running a build of Linus' master branch as of some
time this morning. Without this patch applied I have no audio and suspend
fails leaving the system unresponsive but the keyboard light still on and
the fan running indefinitely. With this patch, I get audio and
suspend/resume works normally.

--Jason Ekstrand
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at