On May 2, 2006, at 17:49:08, Kay Sievers wrote:
If you can assume that processes accessing the values are
cooperative, it already works without any changes:
$ time flock /sys/class/firmware echo 1 > /sys/class/firmware/
timeout
real 0m0.005s
$ flock /sys/class/firmware sleep 5&
[1] 6468
$ time flock /sys/class/firmware echo 1 > /sys/class/firmware/
timeout
real 0m3.558s
But that doesn't solve the problem for framebuffer devices or for the
s390 code. Such transactions have one or more of the following
properties:
(1) A read operation is _expensive_ or adds unacceptable latencies
and should be done as rarely as possible
(2) The data must be all written to hardware simultaneously by the
kernel; a partial update does not make sense and would cause
undesired operation from the hardware.
The idea with the transactions would be to create a kernel-memory
buffer-layer of sorts on top of the underlying sysfs tree to cache
the read data and collect writes for an atomic commit. I'll see if I
can make something work.
Cheers,
Kyle Moffett
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