Re: [PATCH 2/2] of: partition: Use mtd partitioning for of_fixup instead of the cdev variant

[Sascha Hauer <s.hauer@pengutronix.de>]

On Fri, Mar 08, 2024 at 11:14:28AM +0100, Uwe Kleine-König wrote:
> Hello,
> 
> On Fri, Mar 08, 2024 at 10:27:21AM +0100, Ahmad Fatoum wrote:
> > On 08.03.24 10:15, Uwe Kleine-König wrote:
> > > From: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
> > > 
> > > It was already noticed in commit 9d42c77f126e ("devfs: take into account
> > > for the partitions check that mtd is different") that the partitioning
> > > info is stored differently for mtd devices. Instead of only getting the
> > > partion size from the right spot, use the right data completely.
> > 
> > I read both this commit message and that of the referenced commit and I
> > don't quite understand what the issue is. Could you add a short sentence
> > about what particular issue this fix addresses?
> 
> The situation fixed here is:
> 
> After bootup the partitioning information for mtd devices exists in both
> locations (cdev->partitions and cdev->mtd->partitions). An interactive
> addpart only adds the the latter. This patch fixes the of fixup to also
> use the latter.

I don't think this is true. Looking at __devfs_add_partition() we have:

	if (IS_ENABLED(CONFIG_MTD) && cdev->mtd) {
		struct mtd_info *mtd;

		mtd = mtd_add_partition(cdev->mtd, offset, size,
				partinfo->flags, partinfo->name);
		if (IS_ERR(mtd))
			return (void *)mtd;

		list_add_tail(&mtd->cdev.partition_entry, &cdev->partitions);
		return &mtd->cdev;
	}

	...

	list_add_tail(&new->partition_entry, &cdev->partitions);

So all partitions end up in the &cdev->partitions list.

of_fixup_partitions() currently iterates over &cdev->partitions, but it
has:

	if (!(partcdev->flags & DEVFS_PARTITION_FROM_OF))
		continue;

And I think this is your problem. The newly created partition is ignored
during fixup because it doesn't have the DEVFS_PARTITION_FROM_OF flag
set. What you do is a complicated way of ignoring this flag in your
additional iteration over &cdev->partitions.

Sascha

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