mainlining shenanigans
286f3f4787
Because HID_DG_TOOLSERIALNUMBER doesn't first cast the value recieved from HID
to an unsigned type, sign-extension rules can cause the value of
wacom_wac->serial[0] to inadvertently wind up with all 32 of its highest bits
set if the highest bit of "value" was set.
This can cause problems for Tablet PC devices which use AES sensors and the
xf86-input-wacom userspace driver. It is not uncommon for AES sensors to send a
serial number of '0' while the pen is entering or leaving proximity. The
xf86-input-wacom driver ignores events with a serial number of '0' since it
cannot match them up to an in-use tool. To ensure the xf86-input-wacom driver
does not ignore the final out-of-proximity event, the kernel does not send
MSC_SERIAL events when the value of wacom_wac->serial[0] is '0'. If the highest
bit of HID_DG_TOOLSERIALNUMBER is set by an in-prox pen which later leaves
proximity and sends a '0' for HID_DG_TOOLSERIALNUMBER, then only the lowest 32
bits of wacom_wac->serial[0] are actually cleared, causing the kernel to send
an MSC_SERIAL event. Since the 'input_event' function takes an 'int' as
argument, only those lowest (now-cleared) 32 bits of wacom_wac->serial[0] are
sent to userspace, causing xf86-input-wacom to ignore the event. If the event
was the final out-of-prox event, then xf86-input-wacom may remain in a state
where it believes the pen is in proximity and refuses to allow other devices
under its control (e.g. the touchscreen) to move the cursor.
It should be noted that EMR devices and devices which use both the
HID_DG_TOOLSERIALNUMBER and WACOM_HID_WD_SERIALHI usages (in that order) would
be immune to this issue. It appears only AES devices are affected.
Fixes:
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||
|---|---|---|
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| firmware | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
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.