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A recent patch incorrectly altered the adb-iop state machine behaviour
and introduced a regression that can appear intermittently as a
malfunctioning ADB input device. This seems to be caused when reply
packets from different ADB commands become mixed up, especially during
the adb bus scan. Fix this by unconditionally entering the awaiting_reply
state after sending an explicit command, even when the ADB command won't
generate a reply from the ADB device.
It turns out that the IOP always generates reply messages, even when the
ADB command does not produce a reply packet (e.g. ADB Listen command).
So it's not really the ADB reply packets that are being mixed up, it's the
IOP messages that enclose them. The bug goes like this:
1. CPU sends a message to the IOP, expecting no response because this
message contains an ADB Listen command. The ADB command is now
considered complete.
2. CPU sends a second message to the IOP, this time expecting a
response because this message contains an ADB Talk command. This
ADB command needs a reply before it can be completed.
3. adb-iop driver receives an IOP message and assumes that it relates
to the Talk command. It's actually an empty one (with flags ==
ADB_IOP_EXPLICIT|ADB_IOP_TIMEOUT) for the previous command. The
Talk command is now considered complete but it gets the wrong reply
data.
4. adb-iop driver gets another IOP response message, which contains
the actual reply data for the Talk command, but this is dropped
(the driver is no longer in awaiting_reply state).
Cc: Joshua Thompson <funaho@jurai.org>
Fixes:
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|---|---|---|
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
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.