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8730f45d1c
The way the mask value is programmed for QMAP RX endpoints was based on some wrong assumptions about the way metadata containing the QMAP mux_id value is formatted. The metadata value supplied by the modem is *not* in QMAP format, and in fact contains the mux_id we want in its (big endian) low-order byte. That byte must be written by the IPA into offset 1 of the QMAP header it inserts before the received packet. QMAP TX endpoints *do* use a QMAP header as the metadata sent with each packet. The modem assumes this, and based on that assumes the mux_id is in the second byte. To match those assumptions we must program the modem TX (QMAP) endpoint HDR register to indicate the metadata will be found at offset 0 in the message header. The previous configuration managed to work, but it was not working correctly. This patch fixes a bug whose symptom was receipt of messages containing the wrong QMAP mux_id. In fixing this, get rid of ipa_rmnet_mux_id_metadata_mask(), which was more or less defined so there was a separate place to explain what was happening as we generated the mask value. Instead, put a longer description of how this works above ipa_endpoint_init_hdr(), and define the metadata mask to use as a simple constant. Signed-off-by: Alex Elder <elder@linaro.org> Signed-off-by: David S. Miller <davem@davemloft.net>
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.