From patchwork Sat Feb 26 22:06:38 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Jason A. 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Donenfeld" To: Len Brown , "Rafael J. Wysocki" Cc: "Jason A. Donenfeld" , linux-crypto@vger.kernel.org, linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org, Alexander Graf , Ard Biesheuvel , Greg Kroah-Hartman Subject: [PATCH v5 2/3] ACPI: allow longer device IDs Date: Sat, 26 Feb 2022 23:06:38 +0100 Message-Id: <20220226220639.1173594-3-Jason@zx2c4.com> In-Reply-To: <20220226220639.1173594-1-Jason@zx2c4.com> References: <20220226220639.1173594-1-Jason@zx2c4.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-crypto@vger.kernel.org From: Alexander Graf We create a list of ACPI "PNP" IDs which contains _HID, _CID, and CLS entries of the respective devices. However, we squeeze them into struct acpi_device_id, which only has 9 bytes space to store the identifier. It originally had 16 bytes, but was changed to only have 9 in 6543becf26ff ("mod/file2alias: make modalias generation safe for cross compiling"), presumably on the theory that it would match the ACPI spec so it didn't matter. Unfortunately, while most people adhere to the ACPI specs, Microsoft decided that its VM Generation Counter device [1] should only be identifiable by _CID with a value of "VM_Gen_Counter", which is longer than 9 characters. To allow device drivers to match identifiers that exceed the 9 byte limit, this simply ups the length to 16, just like it was before the aforementioned commit. Empirical testing indicates that this doesn't actually increase vmlinux size, because the ulong in the same struct caused there to be 7 bytes of padding anyway. This patch is a prerequisite to add support for VMGenID in Linux, the subsequent patch in this series. It has been confirmed to also work on the udev/modalias side in userspace. [1] https://download.microsoft.com/download/3/1/C/31CFC307-98CA-4CA5-914C-D9772691E214/VirtualMachineGenerationID.docx Cc: Ard Biesheuvel Cc: Len Brown Cc: Rafael J. Wysocki Cc: Greg Kroah-Hartman Co-authored-by: Jason A. Donenfeld Signed-off-by: Alexander Graf Signed-off-by: Jason A. Donenfeld --- Hi Rafael & Len, This patchset is directed toward you two specifically. Patches 1/3 and 3/3 have been through the ringer of review a bit already and do not specifically require your attention, but in v4 we wound up getting hung up on an ACPI API limitation. This v5 fixes that limitation with this 2/3 patch that you see here, with a trivial one line fix, which does require your attention. Patches 1/3 and 3/3 will go through my random.git tree. However, 3/3 actually depends on this one here, 2/3, in order to compile without warnings (and be functional at all). Therefore, it would be nice if you would provide an "Acked-by" on it and permit me to /also/ take it through my random.git tree (if it looks like a correct patch to you, of course). This would make the merge logistics a lot easier. Plus it's a small +1/-1 line change. Please have a look and let me know what you think. Thanks, Jason include/linux/mod_devicetable.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/include/linux/mod_devicetable.h b/include/linux/mod_devicetable.h index 4bb71979a8fd..5da5d990ff58 100644 --- a/include/linux/mod_devicetable.h +++ b/include/linux/mod_devicetable.h @@ -211,7 +211,7 @@ struct css_device_id { kernel_ulong_t driver_data; }; -#define ACPI_ID_LEN 9 +#define ACPI_ID_LEN 16 struct acpi_device_id { __u8 id[ACPI_ID_LEN];