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Converting a Uniprocessor Driver

As a general approach, you can convert a uniprocessor driver to make it multiprocessor-safe in the following steps:

  1. If it currently uses the D_OLD flag (or has no pfxdevflag constant), convert it to use the current interface, with a pfxdevflag of 0x00.

  2. Make sure it works in the original uniprocessor at the current release of IRIX.

  3. Test it in a multiprocessor running in CPU 0.

  4. Begin adding semaphores, locks, and other exclusion and synchronization tools. Since the driver still runs serially on CPU 0, it will never wait for a lock, but the coordination between upper half and interrupt handler should work.

  5. Add the D_MP flag and test on a multiprocessor.
In performing the conversion, you can use calls to spl..() functions as signs that work is needed. These functions are used for mutual exclusion in a uniprocessor, and they are all ineffective or unnecessary in a multiprocessor-safe driver.

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