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Date:   Thu, 20 Jan 2022 10:39:46 +0100
From:   Miquel Raynal <miquel.raynal@bootlin.com>
To:     Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>
Cc:     Trevor Woerner <twoerner@gmail.com>,
        linux-mtd <linux-mtd@lists.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Richard Weinberger <richard@nod.at>,
        Vignesh Raghavendra <vigneshr@ti.com>
Subject: Re: [PATCH 0/3] mtdblock: Advertise about UBI and UBI block
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        <20211026150350.GA5136@localhost>
        <CAAEAJfD0ctKon7onbj5cCgN9OUnXpQ-gxG=DF6hXD9hW+Pw83A@mail.gmail.com>
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Hi Ezequiel,

ezequiel@vanguardiasur.com.ar wrote on Fri, 12 Nov 2021 10:54:36 -0300:

> 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@gmail.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 of outdated tutorials I believe some advertising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@20000   { label = "uboot";     reg = <0x00020000 0x00060000>; };
> >         mtd2@80000   { label = "fbkernel";  reg = <0x00080000 0x003c0000>; };
> >         mtd3@440000  { label = "fbrootfs";  reg = <0x00440000 0x004e0000>; };
> >         mtd4@920000  { label = "c_kernel";  reg = <0x00920000 0x003c0000>; };
> >         mtd5@ce0000  { label = "c__atags";  reg = <0x00ce0000 0x00020000>; };
> >         mtd6@d00000  { label = "c_rootfs";  reg = <0x00d00000 0x00300000>; };
> >         mtd7@1000000 { 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.

I keep getting complaints about these messages because they are
spawned several times in a boot (each device or partition, I don't
recall) while mtdblock is not even used. I understand it would be best
to have it disabled in this case but could we find a way to be less
invasive?

Thanks,
Miquèl