[SOLVED] Cannot access Raspberry Pi Pico filesystem

[nikbott]

Already followed the USB/Guide at the wiki and enabled all relevant kernel opts. Filesystem-wise there's few information online, but from what I found it's apparently a FAT16, which is compiled into the kernel as well.

The kernel appears to recognize the device:

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[   32.180625] usb 1-1.3: new full-speed USB device number 4 using ehci-pci
[   32.260729] usb-storage 1-1.3:1.0: USB Mass Storage device detected
[   32.260819] scsi host7: usb-storage 1-1.3:1.0
[   33.274668] scsi 7:0:0:0: Direct-Access     RPI      RP2              1    PQ: 0 ANSI: 2
[   33.275566] sd 7:0:0:0: [sdd] 262144 512-byte logical blocks: (134 MB/128 MiB)
[   33.276572] sd 7:0:0:0: [sdd] Write Protect is off
[   33.276574] sd 7:0:0:0: [sdd] Mode Sense: 03 00 00 00
[   33.277570] sd 7:0:0:0: [sdd] No Caching mode page found
[   33.277572] sd 7:0:0:0: [sdd] Assuming drive cache: write through
[   33.288574] sd 7:0:0:0: [sdd] Attached SCSI removable disk

lsblk shows the block device, but ignores any partitions:

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sdd      8:48   1   128M  0 disk

so when trying to mount, it fails:

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mount: /mnt/pico: wrong fs type, bad option, bad superblock on /dev/sdd, missing codepage or helper program, or other error.

[fedeliallalinea]

Moved from Kernel & Hardware to Gentoo on ARM.

[NeddySeagoon]

nikbott,

That suggests that you don't have the right sort of partition table support in your kernel.

Is there actually a partition table on the device or is it a big floppy?
What happens if to try to mount /dev/sdd (no partition number)

What does

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fdisk -l /dev/sdd

say about the partition table?
Jibberish means that there is none, which I'm half expecting.

[nikbott]

The error when mounting /dev/sdd is the one i complained above, namely:

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mount: /mnt/pico: wrong fs type, bad option, bad superblock on /dev/sdd, missing codepage or helper program, or other error. 

Also, it really seems to have one FAT16 partition, /dev/sdd1, which is completely ignored by the kernel, as seen on lsblk.

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Disk /dev/sdd: 128 MiB, 134217728 bytes, 262144 sectors
Disk model: RP2
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x000938fc

Device     Boot Start    End Sectors  Size Id Type
/dev/sdd1           1 262143  262143  128M  e W95 FAT16 (LBA)

The kernel is compiled with these options regarding FAT filesystems:

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# DOS/FAT/EXFAT/NT Filesystems
CONFIG_FAT_FS=y
CONFIG_VFAT_FS=y
CONFIG_FAT_DEFAULT_CODEPAGE=437
CONFIG_FAT_DEFAULT_IOCHARSET="iso8859-1"
# CONFIG_FAT_DEFAULT_UTF8 is not set
CONFIG_EXFAT_FS=y
CONFIG_EXFAT_DEFAULT_IOCHARSET="utf8"
# end of DOS/FAT/EXFAT/NT Filesystems

[NeddySeagoon]

nikbott,

What does

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grep MSDOS /usr/src/linux/.config

tell?

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$ grep MSDOS /usr/src/linux/.config
CONFIG_MSDOS_PARTITION=y
CONFIG_MSDOS_FS=m

It looks like you have a partition that starts at byte 512.

Cheat.

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mount -o ro,offset=512 /dev/sdd /mnt/<someplace>

That really is sdd above. The command says to mount read only the filesystem that starts 512b from the start of sdd.
That's what fdisk tells us. (No partition table required.)
The -o ro is a safety measure to get started.

[nikbott]

Here is the output of the grep:

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# CONFIG_MSDOS_PARTITION is not set
CONFIG_MSDOS_FS=y

Also, mounting with 512b offset seemed to work, but is there any trick to do that automatically (fstab or something)?

[NeddySeagoon]

nikbott,

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# CONFIG_MSDOS_PARTITION is not set

Is the problem. Your kernel cannot understand the partition table on /dev/sdd.

Fix that and you will have a /dev/sdd1 to mount.

You can probably put offset=512 into options in fstab but its not the right fix.

[nikbott]

Yeah, recompiled the kernel and now it mounts flawlessly. Thanks!