Re: SDHCI Driver

From what I have read I want to base this off an IOBlockStorageDevice. Is this the best choice or should I base my driver off some other class?

Yes, it is the best choice.

Is there any example code showing how to do something simple like implement a ram drive and have it attached to the file system stack? If IOBlockStorageDevice is the best class, then is it as simple as creating my own versions of the various virtual functions?

Override the virtual functions, yes. After you allocate, init, and attach your subclass of IOBlockStorageDevice, all you need to do is call registerService() on it. IOKit will handle the rest.

Something like this (error checking removed for brevity):

IOService * mySubclass = OSTypeAlloc ( MySubclass );

mySubclass->init();

mySubclass->attach ( this );

mySubclass->registerService();

mySubclass->release();

How do I let the system know I want this to tie in to the rest of the file system stack, for example I see myself writing a single driver to handle both the transport and physical interconnect layers(will separate later), but how does the system know to tie these into the Device services layer above?

There's no reason to separate your driver into two layers if it's not required. By following the example above (with added error checking), IOKit will find your subclass of IOBlockStorageDevice and match the appropriate driver (IOBlockStorageDriver). IOBlockStorageDriver will make calls into your IOBlockStorageDevice subclass to find out the media block size, number of blocks, etc.

Sorry for all the newbie questions, but this is my first driver in the desktop word, I come from a much simpler embedded world and I'm not use to starting with so much work done for me.

Good luck!

-- Chris

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References:
	>SDHCI Driver (From: Reggie McMurtrey <email@hidden>)