• Christoph Hellwig's avatar
    IB: add a proper completion queue abstraction · 14d3a3b2
    Christoph Hellwig authored
    This adds an abstraction that allows ULPs to simply pass a completion
    object and completion callback with each submitted WR and let the RDMA
    core handle the nitty gritty details of how to handle completion
    interrupts and poll the CQ.
    
    In detail there is a new ib_cqe structure which just contains the
    completion callback, and which can be used to get at the containing
    object using container_of.  It is pointed to by the WR and WC as an
    alternative to the wr_id field, similar to how many ULPs already use
    the field to store a pointer using casts.
    
    A driver using the new completion callbacks allocates it's CQs using
    the new ib_create_cq API, which in addition to the number of CQEs and
    the completion vectors also takes a mode on how we poll for CQEs.
    Three modes are available: direct for drivers that never take CQ
    interrupts and just poll for them, softirq to poll from softirq context
    using the to be renamed blk-iopoll infrastructure which takes care of
    rearming and budgeting, or a workqueue for consumer who want to be
    called from user context.
    
    Thanks a lot to Sagi Grimberg who helped reviewing the API, wrote
    the current version of the workqueue code because my two previous
    attempts sucked too much and converted the iSER initiator to the new
    API.
    Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
    14d3a3b2
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