Support file system statistics

[Slion]

Would be great to be able to get statistics from the file system.
For littlefs this is done through lfs_fs_stat and lfs_fs_size.

See: littlefs-project/littlefs#45

[Slion]

Thankfully, using our knowledge to that the littlefs struct is at offset zero in our fs context we can conveniently call littlefs functions like that:

#include <stdio.h>
#include <string.h>
#include <hardware/clocks.h>
#include <hardware/flash.h>
#include <pico/filesystem.h>
#include <pico/filesystem/blockdevice/flash.h>
#include <pico/filesystem/blockdevice/sd.h>
#include <pico/filesystem/filesystem/fat.h>
#include <pico/filesystem/filesystem/littlefs.h>
#include <pico/btstack_flash_bank.h>
#include <lfs.h>

blockdevice_t* flash;
filesystem_t *lfs;


/// @brief Print our file system info
/// Looks like littlefs does not need one sector per file.
/// It is likely capable of packing multiple files per sector.
/// This is going to be very useful.
void fs_log_info()
{
    struct lfs_fsinfo fsinfo;
    memset(&fsinfo,0,sizeof(fsinfo));
    lfs_fs_stat(lfs->context,&fsinfo);
    lfs_size_t usedBlockCount = lfs_fs_size(lfs->context);
    printf("FS: block count: %d\n",fsinfo.block_count);
    printf("FS: used / total: %dkB / %dkB\n", (usedBlockCount * fsinfo.block_size)/1024, (fsinfo.block_count * fsinfo.block_size)/1024);
    printf("FS: %dkB available from %d blocks\n", (fsinfo.block_count * fsinfo.block_size - usedBlockCount * fsinfo.block_size)/1024, fsinfo.block_count - usedBlockCount);
}

bool fs_init(void)
{
    // Don't overwrite btstack storage
    size_t eof = PICO_FLASH_BANK_STORAGE_OFFSET;
    size_t size = FLASH_SECTOR_SIZE * 10u;
    flash = blockdevice_flash_create(eof-size, size);
    lfs = filesystem_littlefs_create(500, 16);

    int err = fs_mount("/", lfs, flash);
    if (err!=0)
    {
        printf("FS: formatting \n");
        fs_format(lfs,flash);
        err = fs_mount("/", lfs, flash);
    }

    printf("FS: fs_mount: %d :%s\n", err, fs_strerror(err));

    if (err==0)
    {
        fs_log_info();
        return true;
    }

    return false;
}

[oyama]

I am wondering how to support this information for various file systems other than littlefs. We would probably only need to cover littlefs and FatFs, so we would like to be able to get basic information.

[oyama]

I can get the same information from FatFs, which is fine!
http://elm-chan.org/fsw/ff/doc/getfree.html