sdcard: Updating sector calculation for SDXC.

[benwynn]

The current code only calculates sectors for SDHC, with a max of 32G
The new code will calculate sectors for SDXC, with a max of 2T

C_SIZE is 22 bits[69:48] and the high 2 bits of csd[7] are required
to be 0, currently, so i'm not masking them off.

The max value for C_SIZE is 0x3FFEFF, so C_SIZE+1*1024 is a 32-bit number.

[benwynn]

will fix issue #1053

[AJMansfield]

Is there anything you could do to add a test for this to sdtest.py?

[benwynn]

Is there anything you could do to add a test for this to sdtest.py?

I'd be happy to work on it... is there a framework for mocking out the hardware, or is that test run against a particular sdcard?

[AJMansfield]

I think it's just run against real hardware, though of no particular spec; changing the test to one that requires SDXC hardware to pass isn't an issue. (From experience, it's actually more difficult to get non-SDXC cards these days...)

As for what operation to actually test with, you're probably more familiar than I here --- but the thought that comes to mind is if there's a way to attempt to operate on a large sparse file or a small file that's in a high-numbered sector past the end of the max SDHC sector number. If the only way to actually exercise this change is to write >32GB of data though, that should probably be added as a second test that isn't run by default --- but having the test code already prepared will make it a lot easier for a maintainer to verify the change either way.