linux-kernel - Re: [PATCH 0/3] mtdblock: Advertise about UBI and UBI block

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Date:   Fri, 12 Nov 2021 10:54:36 -0300
From:   Ezequiel Garcia <ezequiel@...guardiasur.com.ar>
To:     Trevor Woerner <twoerner@...il.com>
Cc:     Ezequiel Garcia <ezequiel@...labora.com>,
        linux-mtd <linux-mtd@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Richard Weinberger <richard@....at>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Vignesh Raghavendra <vigneshr@...com>
Subject: Re: [PATCH 0/3] mtdblock: Advertise about UBI and UBI block

Hi Trevor,

I am not reachable at ezequiel at collabora.com, so I missed this
thread. Sorry about the delay, replying.

On Tue, 26 Oct 2021 at 12:05, Trevor Woerner <twoerner@...il.com> wrote:
>
> On Sun 2021-08-01 @ 08:45:02 PM, Ezequiel Garcia wrote:
> > Hi Richard, and everyone else:
> >
> > Browsing the internet for "JFFS2 mtd" results in tutorials, articles
> > and github.gists0 that point to mtdblock.
> >
> > In fact, even the MTD wiki mentions that JFFS2
> > needs mtdblock to mount a rootfs:
> >
> >   http://www.linux-mtd.infradead.org/faq/jffs2.html
> >
> > Moreover, I suspect there may be lots of users
> > that still believe mtdblock is somehow needed to
> > mount SquashFS.
> >
> > I've taken a verbose route and added a pr_warn
> > warning if the devices are NAND. I don't think using
> > NAND without UBI is too wise, and given the amount
> > of outdated tutorials I believe some advertising
> > will help.
>
> Not all NAND partitions on a device will contain linux root filesystems. For a
> linux root filesystem perhaps using UBI/UBIFS is preferred, yet these messages
> print out for each and every NAND partition:
>
>         [    0.900827] Creating 8 MTD partitions on "nxp_lpc3220_slc":
>         [    0.906431] 0x000000000000-0x000000020000 : "bootrom"
>         [    0.913523] mtdblock: MTD device 'bootrom' is NAND, please consider using UBI block devices instead.
>         [    0.933334] 0x000000020000-0x000000080000 : "uboot"
>         [    0.940439] mtdblock: MTD device 'uboot' is NAND, please consider using UBI block devices instead.
>         [    0.963322] 0x000000080000-0x000000440000 : "fbkernel"
>         [    0.970655] mtdblock: MTD device 'fbkernel' is NAND, please consider using UBI block devices instead.
>         [    0.993361] 0x000000440000-0x000000920000 : "fbrootfs"
>         [    1.000725] mtdblock: MTD device 'fbrootfs' is NAND, please consider using UBI block devices instead.
>         [    1.023315] 0x000000920000-0x000000ce0000 : "c_kernel"
>         [    1.030722] mtdblock: MTD device 'c_kernel' is NAND, please consider using UBI block devices instead.
>         [    1.053444] 0x000000ce0000-0x000000d00000 : "c__atags"
>         [    1.060742] mtdblock: MTD device 'c__atags' is NAND, please consider using UBI block devices instead.
>         [    1.083349] 0x000000d00000-0x000001000000 : "c_rootfs"
>         [    1.090702] mtdblock: MTD device 'c_rootfs' is NAND, please consider using UBI block devices instead.
>         [    1.113335] 0x000001000000-0x000020000000 : "mender"
>         [    1.131627] mtdblock: MTD device 'mender' is NAND, please consider using UBI block devices instead.
>
> NAND tends to be something found on older devices, the firmware/bootloaders
> of older devices couldn't possibly understand UBI/UBIFS so many of these
> partitions need be "raw" partitions, or use something that predates UBI.
>
> Ironically my "mender" partition contains a UBI (with multiple UBIFSes inside)
> yet I got the same "please use UBI" message as all the others (lol)
>
> I'm specifying my partitions in DT with:
>
> partitions {
>         compatible = "fixed-partitions";
>         #address-cells = <1>;
>         #size-cells = <1>;
>
>         mtd0@0       { label = "bootrom";   reg = <0x00000000 0x00020000>; };
>         mtd1@...00   { label = "uboot";     reg = <0x00020000 0x00060000>; };
>         mtd2@...00   { label = "fbkernel";  reg = <0x00080000 0x003c0000>; };
>         mtd3@...000  { label = "fbrootfs";  reg = <0x00440000 0x004e0000>; };
>         mtd4@...000  { label = "c_kernel";  reg = <0x00920000 0x003c0000>; };
>         mtd5@...000  { label = "c__atags";  reg = <0x00ce0000 0x00020000>; };
>         mtd6@...000  { label = "c_rootfs";  reg = <0x00d00000 0x00300000>; };
>         mtd7@...0000 { label = "mender";    reg = <0x01000000 0x1f000000>; };
> };
>
> which is why, I assume, I'm getting these messages. Is there a UBI-friendly
> way to define them to avoid these messages?
>

I feel the messages are actually helping you. You should not have mtdblock
on any of these MTD devices, if I understood correctly, since you are not
mounting a filesystem on any of them.

Just disable MTDBLOCK on your build and you will be good to go.

I am inclined to just leave the warnings, although they look spammy,
precisely to help catch this mis-setups.

Thanks,
Ezequiel