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Establish a queue mapping between the DSA slave network device queues created that correspond to switch port queues, and the transmit queue that SYSTEMPORT manages. We need to configure the SYSTEMPORT transmit queue with the switch port number and switch port queue number in order for the switch and SYSTEMPORT hardware to utilize the out of band congestion notification. This hardware mechanism works by looking at the switch port egress queue and determines whether there is enough buffers for this queue, with that class of service for a successful transmission and if not, backpressures the SYSTEMPORT queue that is being used. For this to work, we implement a notifier which looks at the DSA_PORT_REGISTER event. When DSA network devices are registered, the framework calls the DSA notifiers when that happens, extracts the number of queues for these devices and their associated port number, remembers that in the driver private structure and linearly maps those queues to TX rings/queues that we manage. This scheme works because DSA slave network deviecs always transmit through SYSTEMPORT so when DSA slave network devices are destroyed/brought down, the corresponding SYSTEMPORT queues are no longer used. Also, by design of the DSA framework, the master network device (SYSTEMPORT) is registered first. For faster lookups we use an array of up to DSA_MAX_PORTS * number of queues per port, and then map pointers to bcm_sysport_tx_ring such that our ndo_select_queue() implementation can just index into that array to locate the corresponding ring index. Signed-off-by: Florian Fainelli <f.fainelli@gmail.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.