SD card Mutex

[Duggle]

The module documentation at uCApps clearly states that a mutex must be used to ensure mutual exclusion between tasks that may be attempting to access the sd card.

But can calls to FILE_SDCardAvailable() be made without taking/giving the mutex?

[Duggle]

It seems that FILE_SDCardAvailable() returns the value of a flag, so calling this function from different tasks should not require the use of a semaphore.

[TK.]

Yes, correct.

The flag is set by FILE_CheckSDCard which should be frequently called and should be protected via Mutex

Note that the Mutex is only required if the SPI port is shared with another device (e.g. MBHP_ETH interface)

Best Regards, Thorsten.

[Duggle]

Presumably, mutexs are required when ever two or more tasks are accessing the same data structures (with the possibility of incomplete changes being seen by the other task(s)).

I think I've been using the SD Card mutex to prevent mutliple processes from simultaneous access to file structures. I have a settings save/restore mechanism that is called from different tasks as well as a data logging facility.

I suppose that I should have separate mutexs to remove the potential for bottlenecks. (Although I dont see performance being an issue).

[TK.]

Of course, you are right, in this case the usage of a Mutex is required as well.

I mixed this with the mutex which is mentioned in the MIOS32 documentation (MIOS32_SPI).

The only reason for not using mutexes would be to keep the code as simple as possible - but once you learned how to setup them, there is no reason for not using this "protection" mechanism.

Best Regards, Thorsten.