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When firmware sends a DMA response to the driver, the last byte of the message will be set to 1 to indicate that the whole response is valid. The driver waits for the message to be valid before reading the message. The firmware spec allows these response messages to increase in length by adding new fields to the end of these messages. The older spec's valid location may become a new field in a newer spec. To guarantee compatibility, the driver should zero the valid byte before interpreting the entire message so that any new fields not implemented by the older spec will be read as zero. For messages that are forwarded to VFs, we need to set the length and re-instate the valid bit so the VF will see the valid response. Signed-off-by: Michael Chan <michael.chan@broadcom.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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.