On Wed, May 13, 2015 at 01:38:59AM +0200, Rafael J. Wysocki wrote: > On Tuesday, May 12, 2015 10:43:33 AM Matthew Garrett wrote: > > On Tue, May 12, 2015 at 10:29 AM, Mario Limonciello > > <mario_limonciello@xxxxxxxx> wrote: > > > Just to be clear, from the Dell side only the XPS 13 9343 has this _REV > > > behavior. > > > > The Inspiron 7437 queries _REV and uses it to modify its EC behaviour, > > and apparently breaks on Linux without that. > > > > > What's wrong with a DMI quirk until I2S is mature on the kernel side and > > > userspace is new enough in distros? Is it too early in boot for DMI quirks? > > > That would enforce that no other machines can use _REV value of 5 to detect > > > Linux without breaking the 9343. > > > > DMI quirking is fine, but it has to be behind a config option. We're > > going to have to carry the quirk for several years because we have to > > support old userspace for an arbitrarily long time, and if there's no > > config option then Linux will be stuck in HDA mode for that entire > > time. > > One problem with the DMI-based approach is that _REV is constant in ACPICA, > so to be able to return different values from it for different systems, we'll > need to add some ACPICA-ish code handling that specifically for Linux and > we're a bit too late in the cycle for that. > > So here's what I'm going to do. I'll revert commit b1ef29725865 for 4.1, > but *only* for 4.1 (I've actually queued up a revert of it already) and > I'll revert that revert during the 4.2 merge window. Sounds like a good plan. Thanks! > In the meantime, we'll develop the code to implement the DMI-based quirks > for the Dells and apply it for 4.2. > > Are there any volunteers for doing the last part? Will try to prepare patches for that tomorrow. Best, Dominik
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