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Date:   Tue, 26 Oct 2021 11:03:50 -0400
From:   Trevor Woerner <twoerner@gmail.com>
To:     Ezequiel Garcia <ezequiel@collabora.com>
Cc:     linux-mtd@lists.infradead.org, linux-kernel@vger.kernel.org,
        Richard Weinberger <richard@nod.at>,
        Miquel Raynal <miquel.raynal@bootlin.com>,
        Vignesh Raghavendra <vigneshr@ti.com>
Subject: Re: [PATCH 0/3] mtdblock: Advertise about UBI and UBI block
Message-ID: <20211026150350.GA5136@localhost>
References: <20210801234509.18774-1-ezequiel@collabora.com>
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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 of outdated tutorials I believe some advertising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?

Best regards,
	Trevor