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    dmaengine: up-level reference counting to the module level · 6f49a57a
    Dan Williams 提交于
    Simply, if a client wants any dmaengine channel then prevent all dmaengine
    modules from being removed.  Once the clients are done re-enable module
    removal.
    
    Why?, beyond reducing complication:
    1/ Tracking reference counts per-transaction in an efficient manner, as
       is currently done, requires a complicated scheme to avoid cache-line
       bouncing effects.
    2/ Per-transaction ref-counting gives the false impression that a
       dma-driver can be gracefully removed ahead of its user (net, md, or
       dma-slave)
    3/ None of the in-tree dma-drivers talk to hot pluggable hardware, but
       if such an engine were built one day we still would not need to notify
       clients of remove events.  The driver can simply return NULL to a
       ->prep() request, something that is much easier for a client to handle.
    Reviewed-by: NAndrew Morton <akpm@linux-foundation.org>
    Acked-by: NMaciej Sosnowski <maciej.sosnowski@intel.com>
    Signed-off-by: NDan Williams <dan.j.williams@intel.com>
    
    
    6f49a57a
dmaengine.c 21.3 KB