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The commit10cf4899f8("gpiolib: tighten up ACPI legacy gpio lookups") prevents to getting same resource twice if the driver asks twice using different connection ID. But the whole idea of fallback might bring some problems. Imagine the case when we have two versions of BIOS/hardware where in one _DSD is introduced along with GPIO resources, but the other one uses just plain GPIO resource for another purpose Case 1: Device (DEVX) { ... Name (_CRS, ResourceTemplate () { GpioIo (Exclusive, PullUp, 0, 0, IoRestrictionInputOnly, "\\_SB.GPO0", 0, ResourceConsumer) {15} }) Name (_DSD, Package () { ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"), Package () { Package () {"some-gpios", Package() {^DEVX, 0, 0, 0 }}, } }) } Case 2: Device (DEVX) { ... Name (_CRS, ResourceTemplate () { GpioIo (Exclusive, PullUp, 0, 0, IoRestrictionInputOnly, "\\_SB.GPO0", 0, ResourceConsumer) {27} }) } To prevent the possible misconfiguration tighten up even more GPIO ACPI lookups for case without connection ID provided. In the past the issue had been triggered by "use mctrl_gpio helpers" series [1,2]. [1] commit4ef03d3287("tty/serial/8250: use mctrl_gpio helpers") [2] https://patchwork.kernel.org/patch/9283745/ Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com> Cc: Bastien Nocera <hadess@hadess.net> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> Tested-by: Jarkko Nikula <jarkko.nikula@linux.intel.com> Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com> Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.