block devices on MTD and UBI

[Mike Looijmans]

On 19-03-2025 15:06, Heiko Schocher wrote:
> Hello Mike,
>
> On 18.03.25 10:04, Mike Looijmans wrote:
>> I think I have everything set up to access MTD (and UBI) devices as 
>> "block", however, lsblk always ignores them, and refuses to list 
>> anything but the mmc. I can read ubifs and boot from it though, and 
>> since UBI runs on top of MTD block devices, MTD block device should 
>> be working, right?
>
> Yes. I must admit, I have no device on which I have such a setup...
>
> added Alexey (who introduced ubi block support), may he can give some 
> hints.
>
>> I also have UBI_BLOCK enabled, so I would expect UBI volumes to 
>> appear in the "lsblk" as well.
>
> good, that would have been my first question, if you have enabled 
> "UBI_BLOCK"
>
>> Example U-boot session:
>>
>> Zynq> mtd list
>> SF: Detected n25q256ax1 with page size 256 Bytes, erase size 64 KiB, 
>> total 32 MiB
>> List of MTD devices:
>> * nor0
>>    - device: flash at 0
>>    - parent: spi at e000d000
>>    - driver: jedec_spi_nor
>>    - path: /axi/spi at e000d000/flash at 0
>>    - type: NOR flash
>>    - block size: 0x10000 bytes
>>    - min I/O: 0x1 bytes
>>    - 0x000000000000-0x000002000000 : "nor0"
>>            - 0x000000000000-0x000000100000 : "qspi-boot-bin"
>>            - 0x000000100000-0x000002000000 : "qspi-rootfs"
>
> Aha, SPI NOR. I fear this is not supported yet.
>
> Do you have somehow called ubi_part() ?
>
> Can you try "ubi part...." and look if this helps?

See below I guess...


>
>>
>> Zynq> lsblk
>> Block Driver          Devices
>> -----------------------------
>> efi_blk             : <none>
>> mmc_blk             : mmc 0
>> mtd_blk             : <none>
>> ubi_blk             : <none>
>
> Here (and for mtd) seems something missing!
>
>> usb_storage_blk     : <none>
>>
>> Zynq> ubi part qspi-rootfs
>> Zynq> ubi list
>> 0: qspi-rootfs
>> Zynq> lsblk
>> Block Driver          Devices
>> -----------------------------
>> efi_blk             : <none>
>> mmc_blk             : mmc 0
>> mtd_blk             : <none>
>> ubi_blk             : <none>
>> usb_storage_blk     : <none>
>>
>>
>> I would have expected the SPI NOR flash to appear in the "mtd_blk" 
>> devices, and would expect the UBI volumes to appear in the "ubi_blk" 
>> list.
>> What am I missing?
>
> It seems to me, that you have to implement this like it is done for 
> spi nand:
>
> drivers/mtd/nand/spi/core.c
> 1180 static int spinand_bind(struct udevice *dev)
> 1181 {
> 1182         if (blk_enabled()) {
> 1183                 struct spinand_plat *plat = dev_get_plat(dev);
> 1184                 int ret;
> 1185
> 1186                 if (CONFIG_IS_ENABLED(MTD_BLOCK)) {
> 1187                         ret = mtd_bind(dev, &plat->mtd);
> 1188                         if (ret)
> 1189                                 return ret;
> 1190                 }
> 1191
> 1192                 if (CONFIG_IS_ENABLED(UBI_BLOCK))
> 1193                         return ubi_bind(dev);
> 1194         }
> 1195
> 1196         return 0;
> 1197 }
>
I guess that shouldn't be to hard to implement... I'll send a patch if 
that fixes the MTD missing...


> The only thing I just stumbled over is:
>
> drivers/mtd/ubi/block.c
>  35 static struct ubi_device *get_ubi_device(void)
>  36 {
>  37         return ubi_devices[0];
>  38 }
>
> may this is not perfect.

That might be because there can be only one active UBI device anyway.


>
> But as said, I cannot try out ...
>
>> What I'm aiming for here is to be able to:
>> - Read from squashfs in (raw) MTD partition (NOR flash is ideal for 
>> that)
>> - Read kernel/devicetree (fit) from UBI volume
>> - Read from squashfs inside UBI volume
>>
>>
>> I can read files from UBIFS (and boot into Linux using bootcmd_ubifs) 
>> just fine, e.g.:
>> Zynq> ubifsmount ubi0:qspi-rootfs
>> Zynq> ls ubi 0
>> <DIR>        5200  Fri Mar 09 12:34:56 2018  bin
>> <DIR>         160  Fri Mar 09 12:34:56 2018  dev
>> <DIR>        4984  Fri Mar 09 12:34:56 2018  etc
>> ...
>>
>>
>
> Good to hear that UBI/UBIFS setup is working!
>
> So I fear there is some "add feature"/debug work ToDo to get this up and
> working ...
>
Good to know it's just missing and not due to something I broke or missed...

Thanks for your reply.


-- 
Mike Looijmans
System Expert

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