Rockbox General > Rockbox General Discussion

SDXC MBR ID issues

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RBBrittain:

--- Quote from: torne on August 19, 2011, 05:54:25 AM ---Virtually all current operating systems ignore the partition type and just detect the filesystem by probing for superblocks in known formats. We should probably just do that too.

--- End quote ---
I intentionally stepped away from the thread for awhile to let more knowledgeable people discuss it, but I agree that's the best option--as long as it can be done without using a lot more memory (the reason for the NoDo on non-FAT32 filesystems).  That way we can just point users with first-gen SDXC cards (same pinout as SD/SDHC) to any FAT32 formatter that ignores MS' arbitrary 32MB limit, whether it changes the MBR ID or not.  IMO that should be enough to keep the NoDo in place for all existing targets, especially since they will likely never support second-gen SDXC cards (different pins).

torne:
Now that you've reminded me that this thread existed, I have made this change in r30566. There is no RAM issue, it's nothing to do with filesystem support; it's actually slightly less code. :) Any partition type other than 0 or 5 (unallocated and extended, respectively) is checked for a FAT superblock and mounted if it has one.

toehser:
I'm surprised no-one mentioned that you don't have to have a partition table at all - you can just format the _whole device_ to FAT32.

On my Clip-Zip, Clip+, and Fuze-V2 devices, formatting it without a partition table works fine.

It gives a few more K of space, it is easier to loop-mount images, and there certainly can't be issues with the partition ID if you just format the whole device as FAT32 without partitions...

After all, if you aren't ever going to boot from it, and are never going to have more than the one single file system, why not?

bluebrother:

--- Quote from: toehser on April 05, 2012, 11:03:50 AM ---After all, if you aren't ever going to boot from it, and are never going to have more than the one single file system, why not?
--- End quote ---

Not all programs / devices can cope with that. While what you said is true for Rockbox you might run into problems with some devices. Just to give an example, I have a simple DSO that can save screenshots to a uSD card, but it requires the chard to have a partition table.

So in the end it depends on your use case. If you're aware of the differences and know it won't cause problems for your use case there is no reason not to format without a partition table (sometimes called "superfloppy" format).

torne:
Just in case anyone finds this thread later: the fix I referred to in a previous post got reverted, so you do still have to change the partition ID (or format as superfloppy) to use it in Rockbox.

The fix broke mounting superfloppy cards in certain cases, which we need to fix by making our MBR and FAT validation code more robust before the fix can be reapplied.

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