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marqs85 / ossc

Open Source Scan Converter
http://junkerhq.net/xrgb/index.php/OSSC
GNU General Public License v3.0
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Implement userdata export by creating a FAT16 filesystem #75

Closed megari closed 3 years ago

megari commented 3 years ago

This PR implements exporting userdata in an easier-to-use manner, by creating a 16 MiB FAT16 volume on the SD card, with the userdata dump as a file in the root directory.

The code could probably be made smaller by taking additional liberties with regard to the FAT16 specification. Currently, the only violation I know of is that only the first sector of the root directory is zeroed out, apart from the directory entry for the userdata dump.

megari commented 3 years ago

The delta to the previous userdata export PR works out to 546 or 548 bytes. Not a whole lot, but can probably be reduced further.

Previous PR post-build statistics:

   text    data     bss     dec     hex filename
  31956    2936    2652   37544    92a8 sys_controller.elf
riscv32-unknown-elf-objcopy --change-addresses -0x10000 -O binary --gap-fill 0 sys_controller.elf mem_init/sys_onchip_memory2_0.bin
../../tools/bin2hex 4 mem_init/sys_onchip_memory2_0.bin mem_init/sys_onchip_memory2_0.hex
size: 34892 bytes

The current post-build statistics:

   text    data     bss     dec     hex filename
  32502    2936    2652   38090    94ca sys_controller.elf
riscv32-unknown-elf-objcopy --change-addresses -0x10000 -O binary --gap-fill 0 sys_controller.elf mem_init/sys_onchip_memory2_0.bin
../../tools/bin2hex 4 mem_init/sys_onchip_memory2_0.bin mem_init/sys_onchip_memory2_0.hex
size: 35440 bytes
alanbork commented 3 years ago

personally I'd rather save the space for features than file export which I have little expectation to use... but I don't have a sense on how tight space is at this point.

megari commented 3 years ago

personally I'd rather save the space for features than file export which I have little expectation to use... but I don't have a sense on how tight space is at this point.

After some optimization, this feature now requires 446 bytes. This is unlikely to go substantially lower. This leaves a margin of about 2 kB. This may be enough for a few small features in addition to any bugfixes. Let's see how this fits in the roadmap.