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. 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? -- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center. -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
