From: Pintu Agarwal <pintu.ping@gmail.com>
To: Richard Weinberger <richard@nod.at>
Cc: 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>
Subject: Re: MTD: How to get actual image size from MTD partition
Date: Thu, 22 Jul 2021 16:40:26 +0530 [thread overview]
Message-ID: <CAOuPNLhCMT7QTF+QadJyGDFNshH9VjEAzWStRpe8itw7HXve=A@mail.gmail.com> (raw)
In-Reply-To: <2132615832.4458.1626900868118.JavaMail.zimbra@nod.at>
On Thu, 22 Jul 2021 at 02:24, Richard Weinberger <richard@nod.at> wrote:
>
> ----- Ursprüngliche 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=squashfs root=/dev/mtdblock44 ubi.mtd=40,0,30
> > And CONFIG_MTD_UBI_BLOCK=y 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
>
Okay, you mean to say, we should use this ?
ubi.mtd=5 ubi.block=0,0 root=/dev/ubiblock0_0
Instead of this:
root=/dev/mtdblock44 ubi.mtd=40,0,30
Okay I will discuss this internally and check..
> >> If you place your squashfs on a UBI static volume, UBI knows the exact length
> >> and you can checksum it
> >> more easily.
> > Yes, we use squashfs on UBI volumes, but our volume type is still dynamic.
> > Also, you said, UBI knows the exact length, you mean the whole image length ?
> > How can we get this length at runtime ?
>
> You need a static volume for that. If you update a static volume the length is
> known by UBI.
>
Thank you so much for your reply!
Sorry, I could not get this part. How static volume can give image len ?
You mean there is some interface available in kernel to get actual image len ?
> > Also, how can we get the checksum of the entire UBI volume content
> > (ignoring the erased/empty/bad block content) ?
>
> Just read from the volume. /dev/ubiX_Y.
>
I think this also will give the entire volume size, but we still don't know how
many pages have real data ?
For example:
Suppose, my raw partition/volume is of size 10MB
But my actual data inside it is of size ~3MB (may be split across?)
Then, how can we get the actual size of the data content ?
You mean to say: /dev/ubiX_Y should contain only data blocks ?
> > Or, you mean to say, the whole checksum logic is in-built inside the
> > UBI layer and users don't need to worry about the integrity at all ?
>
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next prev parent reply other threads:[~2021-07-22 11:11 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-16 6:42 MTD: How to get actual image size from MTD partition Pintu Agarwal
2021-07-16 7:16 ` Richard Weinberger
2021-07-16 15:41 ` Greg KH
2021-07-16 16:26 ` Richard Weinberger
2021-07-19 9:09 ` Pintu Agarwal
2021-07-19 9:28 ` Richard Weinberger
2021-07-20 6:17 ` Pintu Agarwal
2021-07-20 6:40 ` Richard Weinberger
2021-07-20 8:01 ` Pintu Agarwal
2021-07-21 20:54 ` Richard Weinberger
2021-07-22 11:10 ` Pintu Agarwal [this message]
2021-07-27 21:16 ` Richard Weinberger
2021-07-29 11:17 ` Ezequiel Garcia
2021-07-29 11:45 ` Richard Weinberger
2021-07-29 12:03 ` Ezequiel Garcia
2021-07-29 17:11 ` Pintu Agarwal
2021-08-20 18:24 ` Pintu Agarwal
2021-08-22 14:21 ` Ezequiel Garcia
2021-08-30 15:58 ` Pintu Agarwal
2021-10-29 16:12 ` Pintu Agarwal
2021-10-29 16:48 ` Ezequiel Garcia
2021-11-08 13:51 ` Pintu Agarwal
2021-11-12 13:58 ` Ezequiel Garcia
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