[PATCH] kill mutex in lis

Werner Almesberger werner at openmoko.org
Sat Oct 11 19:50:36 CEST 2008

Sean McNeil wrote:
> This brings up a question I have about the original changes: why
> convert the mutex to a spin lock? What is the benefit?

This was an attempt to solve the problem of trying to grab a mutex
while interrupts were turned off. There seem to be two correct ways
to do all this:

- either use mutexes and a work queue (or equivalent), which was how
  the driver worked in the old days, or

- use spinlocks or similar (*) and take control of handling the low-level
  SPI operations, so that they don't sleep. This is what Andy's
  bitbang-all-the-way does.

(*) Tasklets may actually be a good choice here, since they're pretty
    efficient and allow the "hard" interrupt handler to return quickly.

- Werner

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