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It apears that devices designed around Wacom's G11 chipset (e.g. Lenovo ThinkPad Yoga 260, Lenovo ThinkPad X1 Yoga, Dell XPS 12 9250, Dell Venue 8 Pro 5855, etc.) suffer from a common issue in their HID descriptors. The logical maximum is not updated for the "Contact Identifier" usage, leaving it as just "1" despite these devices being capable of tracking far more touches. Commit 60a221869803 began ignoring usages with out-of-range values, causing problems for devices based on this chipset. Touches after the first will have an out-of-range Contact Identifier, and ignoring that usage will cause the kernel to incorrectly slot each finger's events (along with all the knock-on userspace effects that entails). This commit checks for these buggy descriptors and updates the maximum where required. Prior chipsets have used "255" as the maximum (and the G11, at least, doesn't seem to actually use IDs outside the range of 1..CONTACTMAX) so continue using this value. Cc: stable@vger.kernel.org Fixes: 60a221869803 ("HID: wacom: generic: add support for touchring") Signed-off-by: Jason Gerecke <jason.gerecke@wacom.com> Signed-off-by: Jiri Kosina <jkosina@suse.cz>
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.