• Jonathan Cameron's avatar
    iio:trigger: Experimental kthread tight loop trigger (thread only) · bc2e1126
    Jonathan Cameron authored
    This patch is in response to that of
    Gregor Boirie <gregor.boirie@parrot.com>
    who proposed using a tight kthread within a device driver (be it with the
    support factored out into a helper library) in order to basically spin as
    fast as possible.
    
    It is meant as a talking point rather than a formal proposal of the code
    (though we are heading towards that I think).
    Also gives people some working code to mess around with.
    
    I proposed that this could be done with a trigger with a few constraints
    and this is the proof (be it ugly) of that.
    
    There are some constraints though, some of which we would want to relax
    if this were to move forward.
    
    * Will only run the thread part of the registered pollfunc.  This is to
      avoid the overhead of jumping in and out of interrupt context.  Is the
      overhead significant?  Not certain but feels like it should be!
    
    * This limitation precludes any device that 'must' do some work in
      interrupt context.  However, that is true of few if any drivers and
      I suspect that any that do will be restricted to using triggers they
      provide themselves.  Usually we have a top half mainly to grab a
      timestamp as soon after the dataready type signal as possible.
    Signed-off-by: default avatarJonathan Cameron <jic23@kernel.org>
    Acked-by: default avatarDaniel Baluta <daniel.baluta@intel.com>
    bc2e1126
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