VolToPart use const in fatfs. (IDFGH-13211)

[qwx]

Answers checklist.

• I have read the documentation ESP-IDF Programming Guide and the issue is not addressed there.
• I have updated my IDF branch (master or release) to the latest version and checked that the issue is present there.
• I have searched the issue tracker for a similar issue and not found a similar issue.

General issue report

When I want to use two partition in one emmc, I have to change the code in diskio.c like this.

const PARTITION VolToPart[FF_VOLUMES] = {
    {0, 0},    /* Logical drive 0 ==> Physical drive 0, auto detection */
#if FF_VOLUMES > 1
    {1, 0},    /* Logical drive 1 ==> Physical drive 1, auto detection */
#endif

change to:

const PARTITION VolToPart[FF_VOLUMES] = {
    {0, 1},    /* Logical drive 0 ==> Physical drive 0, Partition 1 */
#if FF_VOLUMES > 1
    {0, 2},    /* Logical drive 1 ==> Physical drive 0, Partition 2 */
#endif

Everyone coding with me have to change them too.
So is there a way not change the code in esp-idf but in user code?
Like make VolToPart not const or other beautiful way to do this?

[adokitkat]

Yes, this is something which can be improved. Right now creating more partitions on the same storage device is not trivial. Will look into this. Thank you for your comment.

[qwx]

Thank you for your reply. I use the code below to create more than one partition on emmc:

    BYTE work[FF_MAX_SS];         /* Working buffer */
    LBA_t plist[] = {90, 10, 0}; 

    FRESULT fres = f_fdisk(0, plist, work);            /* Divide the physical drive 0 */
    if (fres != FR_OK)
    {
        printf("fdisk error");
    }
    fres = f_mkfs("0:", 0, work, sizeof work); /* Create FAT volume on the logical drive 0 */
    if (fres != FR_OK)
    {
        printf("fdisk1 error");
    }
    fres = f_mkfs("1:", 0, work, sizeof work); /* Create FAT volume on the logical drive 1 */
    if (fres != FR_OK)
    {
        printf("fdisk2 error");
    }

I also create a pull request(#14150) to do this change. I can provide infomation if you need. Thanks a lot.