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From:   Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>
Date:   Thu, 29 Jul 2021 08:17:53 -0300
Message-ID: <CAAEAJfCY+X-G=7Oe9NqrJ4yQZ29DBA78jOFAX44GD0g6=s7qhg@mail.gmail.com>
Subject: Re: MTD: How to get actual image size from MTD partition
To:     Richard Weinberger <richard.weinberger@gmail.com>
Cc:     Pintu Agarwal <pintu.ping@gmail.com>,
        Richard Weinberger <richard@nod.at>,
        Kernelnewbies <kernelnewbies@kernelnewbies.org>,
        Greg KH <greg@kroah.com>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        linux-mtd <linux-mtd@lists.infradead.org>,
        Sean Nyekjaer <sean@geanix.com>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        Phillip Lougher <phillip@squashfs.org.uk>
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Hi Richard,

On Tue, 27 Jul 2021 at 18:16, Richard Weinberger
<richard.weinberger@gmail.com> wrote:
>
> On Thu, Jul 22, 2021 at 1:11 PM Pintu Agarwal <pintu.ping@gmail.com> wrot=
e:
> >
> > On Thu, 22 Jul 2021 at 02:24, Richard Weinberger <richard@nod.at> wrote=
:
> > >
> > > ----- Urspr=C3=BCngliche Mail -----
> > > >> But let me advertise ubiblock a second time.
> > > > Sorry, I could not understand about the ubiblock request. Is it
> > > > possible to elaborate little more ?
> > > > We are already using squashfs on top of our UBI volumes (including
> > > > rootfs mounting).
> > > > This is the kernel command line we pass:
> > > > rootfstype=3Dsquashfs root=3D/dev/mtdblock44 ubi.mtd=3D40,0,30
> > > > And CONFIG_MTD_UBI_BLOCK=3Dy is already enabled in our kernel.
> > > > Do we need to do something different for ubiblock ?
> > >
> > > From that command line I understand that you are *not* using squashfs=
 on top of UBI.
> > > You use mtdblock. ubiblock is a mechanism to turn an UBI volume into =
a read-only
> > > block device.
> > > See: http://www.linux-mtd.infradead.org/doc/ubi.html#L_ubiblock
> > >
[snip]

Ouch, so surprised that after all these years someone is doing squashfs/mtd=
block
instead of using ubiblock :-)

Can we patch either Kconfig or add some warn_once on mtdblock
usage, suggesting to use ubiblock instead?

I remember there was still some use case(s) for mtdblock but I can't rememb=
er
now what was it, perhaps we should document the expectations?
(Is that for JFFS2 to mount?)

Thanks,
Ezequiel