• Philippe Bergheaud's avatar
    cxl: Add mechanism for delivering AFU driver specific events · b810253b
    Philippe Bergheaud authored
    This adds an afu_driver_ops structure with fetch_event() and
    event_delivered() callbacks. An AFU driver such as cxlflash can fill
    this out and associate it with a context to enable passing custom AFU
    specific events to userspace.
    
    This also adds a new kernel API function cxl_context_pending_events(),
    that the AFU driver can use to notify the cxl driver that new specific
    events are ready to be delivered, and wake up anyone waiting on the
    context wait queue.
    
    The current count of AFU driver specific events is stored in the field
    afu_driver_events of the context structure.
    
    The cxl driver checks the afu_driver_events count during poll, select,
    read, etc. calls to check if an AFU driver specific event is pending,
    and calls fetch_event() to obtain and deliver that event. This way, the
    cxl driver takes care of all the usual locking semantics around these
    calls and handles all the generic cxl events, so that the AFU driver
    only needs to worry about it's own events.
    
    fetch_event() return a struct cxl_event_afu_driver_reserved, allocated
    by the AFU driver, and filled in with the specific event information and
    size. Total event size (header + data) should not be greater than
    CXL_READ_MIN_SIZE (4K).
    
    Th cxl driver prepends an appropriate cxl event header, copies the event
    to userspace, and finally calls event_delivered() to return the status of
    the operation to the AFU driver. The event is identified by the context
    and cxl_event_afu_driver_reserved pointers.
    
    Since AFU drivers provide their own means for userspace to obtain the
    AFU file descriptor (i.e. cxlflash uses an ioctl on their scsi file
    descriptor to obtain the AFU file descriptor) and the generic cxl driver
    will never use this event, the ABI of the event is up to each individual
    AFU driver.
    Signed-off-by: default avatarPhilippe Bergheaud <felix@linux.vnet.ibm.com>
    Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
    b810253b
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