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d0b619599e
xHCI spec rev. 1.0 allowed the TRB pointer of Missed Service events to be NULL. Having no idea which of the queued TDs were missed and which are waiting, we can only set a flag to skip missed TDs later. But HCs are also allowed to give us pointer to the last missed TRB, and this became mandatory in spec rev. 1.1 and later. Use this pointer, if available, to immediately skip all missed TDs. This reduces latency and risk of skipping-related bugs, because we can now leave the skip flag cleared for future events. Handle Missed Service Error events as 'error mid TD', if applicable, because rev. 1.0 spec excplicitly says so in notes to 4.10.3.2 and later revs in 4.10.3.2 and 4.11.2.5.2. Notes to 4.9.1 seem to apply. Tested on ASM1142 and ASM3142 v1.1 xHCs which provide TRB pointers. Tested on AMD, Etron, Renesas v1.0 xHCs which provide TRB pointers. Tested on NEC v0.96 and VIA v1.0 xHCs which send a NULL pointer. Change inspired by a discussion about realtime USB audio. Link: https://lore.kernel.org/linux-usb/76e1a191-020d-4a76-97f6-237f9bd0ede0@gmx.net/T/ Signed-off-by: Michal Pecio <michal.pecio@gmail.com> Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com> Link: https://lore.kernel.org/r/20250306144954.3507700-7-mathias.nyman@linux.intel.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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 reStructuredText 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.