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Date:   Thu, 28 Oct 2021 09:31:19 -0400
From:   Trevor Woerner <twoerner@gmail.com>
To:     Richard Weinberger <richard@nod.at>
Cc:     Ezequiel Garcia <ezequiel@collabora.com>,
        linux-mtd <linux-mtd@lists.infradead.org>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Miquel Raynal <miquel.raynal@bootlin.com>,
        Vignesh Raghavendra <vigneshr@ti.com>
Subject: Re: [PATCH 0/3] mtdblock: Advertise about UBI and UBI block
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On Tue 2021-10-26 @ 09:01:32 PM, Richard Weinberger wrote:
> Trevor,
> 
> ----- Ursprüngliche Mail -----
> > Von: "Trevor Woerner" <twoerner@gmail.com>
> > An: "Ezequiel Garcia" <ezequiel@collabora.com>
> > CC: "linux-mtd" <linux-mtd@lists.infradead.org>, "linux-kernel" <linux-kernel@vger.kernel.org>, "richard"
> > <richard@nod.at>, "Miquel Raynal" <miquel.raynal@bootlin.com>, "Vignesh Raghavendra" <vigneshr@ti.com>
> > Gesendet: Dienstag, 26. Oktober 2021 17:03:50
> > Betreff: Re: [PATCH 0/3] mtdblock: Advertise about UBI and UBI block
> 
> > 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 of outdated tutorials I believe some advertising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?
> 
> Hmm, maybe it makes sense to advertise it only once and not for each mtdblock device.

Are there known bugs or issues using ubi/jffs2/squashfs on top of mtdblock? Is
mtdblock being deprecated? If so I could certainly understand warning users of
the situation.

Is there a safe/easy way to update an older device in a way that wipes
the entire flash while running from flash? If not then having the kernel
perpetually advertising that I'm not using my flash a certain way isn't very
useful, especially if there aren't any underlying reasons why my usage isn't
valid.