[OpenWrt-Devel] [PATCH v2] fstools: Add support to read-only MTD partitions (eg. recovery images)

[Steve Brown]

Hi Bruno,

Your suggested fix works on my TPLink A7-V5.

diff --git a/target/linux/ath79/image/common-tp-link.mk b/target/linux/ath79/image/common-tp-link.mk
index 9048e8340c..8aa6a5a2be 100644
--- a/target/linux/ath79/image/common-tp-link.mk
+++ b/target/linux/ath79/image/common-tp-link.mk
@@ -71,7 +71,7 @@ endef
 
 define Device/tplink-safeloader-uimage
   $(Device/tplink-safeloader)
-  KERNEL := kernel-bin | append-dtb | lzma | uImageArcher lzma | pad-to 64k
+  KERNEL := kernel-bin | append-dtb | lzma | uImageArcher lzma
 endef
 
 define Device/tplink-loader-okli
diff --git a/target/linux/generic/hack-4.19/401-inherit-parent-partition-access-mode.patch b/target/linux/generic/hack-4.19/401-inherit-parent-partition-access-mode.patch
index 61dd0369a6..85e958acff 100644
--- a/target/linux/generic/hack-4.19/401-inherit-parent-partition-access-mode.patch
+++ b/target/linux/generic/hack-4.19/401-inherit-parent-partition-access-mode.patch
@@ -36,7 +36,7 @@
                parts[i].offset += slave->offset;
  
 +              /* adjust partition mask */
-+              parts[i].mask_flags = !(slave->mtd.flags & MTD_WRITEABLE) ? MTD_WRITEABLE : 0;
++              parts[i].mask_flags = !(slave->mtd.orig_flags & MTD_WRITEABLE) ? MTD_WRITEABLE : 0;
 +
                mtd_add_partition(slave->parent,
                                  parts[i].name,

Thanks,
Steve

On Wed, 2020-01-22 at 12:18 +0100, Bruno Pena wrote:
> Hi Steve,
> 
> Don't waste your time with the previous test request.
> I'll try to test either today/tomorrow the "mtd.orig_flags" approach
> on my device and - if successful - I'll then ask if you can try it on
> your TP-Link.
> 
> Thank you and best regards,
> Bruno Pena
> 
> On Wed, Jan 22, 2020, 11:34 Bruno Pena <brunompena at gmail.com> wrote:
> > Just a small correction on the previous email, there's actually no
> > padding requirement since everything will be read-only!
> > 
> > On Wed, Jan 22, 2020, 11:25 Bruno Pena <brunompena at gmail.com>
> > wrote:
> > > Hi Daniel,
> > > 
> > > I was looking at the code and I think it's possible to relax the
> > > enforcement of the parent access mode.
> > > We can switch from a strict enforcement of the resulting mtd
> > > access mode, to only enforcing the configured access mode (from
> > > the DTS file).
> > > 
> > > This can be achieved by changing from using mtd.flags to
> > > mtd.orig_flags:
> > >     parts[i].mask_flags = !(slave->mtd.orig_flags &
> > > MTD_WRITEABLE) ? MTD_WRITEABLE : 0;
> > > 
> > > With this change we no longer impact builds that do not have a
> > > read-only firmware partition, but we can still enforce it for
> > > those that need it.
> > > One thing to keep in mind is that the padding is still a
> > > requirement for those devices which are building a read-only
> > > firmware partition!
> > > 
> > > Also please note this is not tested, these conclusions are only
> > > based on the analysis of the kernel source code.
> > > 
> > > Best regards,
> > > Bruno Pena
> > > 
> > > 
> > > On Wed, Jan 22, 2020, 10:40 Daniel Golle <daniel at makrotopia.org>
> > > wrote:
> > > > Hi Bruno,
> > > > 
> > > > On Wed, Jan 22, 2020 at 10:22:01AM +0100, Bruno Pena wrote:
> > > > > I would also like to take the opportunity to ask if it's
> > > > worth pursuing
> > > > > this patch if it means that all devices (using mtd) will
> > > > require their
> > > > > partitions to be padded to the blocksize?
> > > > 
> > > > Please try not to introduce that padding, it's quite a big
> > > > impact on
> > > > all devices while only very few (wifi-only device) really need
> > > > that
> > > > change. Instead of wasting flash space by additional padding
> > > > I'd rather
> > > > want to see an OpenWrt-specific kernel-patch to allow a rw
> > > > subpartition
> > > > sitting inside an ro partition or just flatten the mtd
> > > > partitioning.
> > > > What I mean by flatteing is this:
> > > > 
> > > > yout current approach:
> > > > +-----------------------------+
> > > > |          firmware           |
> > > > +--------+--------------------+ 
> > > > |        $       rootfs       |
> > > > | kernel +------+-------------+
> > > > |        $ rom  | rootfs_data |
> > > > +--------+------+-------------+
> > > > 
> > > > here rootfs_data inherigs the read-only from rootfs not being
> > > > block-
> > > > aligned. a better/flat approach would be:
> > > > +-----------------------------+
> > > > |          firmware           |
> > > > +--------+------+-------------+ 
> > > > | kernel $ rom  | rootfs_data |
> > > > +--------+------+-------------+
> > > > 
> > > > Now this would require major changes to our mtd-splitting
> > > > subsystem
> > > > which is quite a big amount of work...
> > > > 
> > > > 
> > > > Cheers
> > > > 
> > > > 
> > > > Daniel


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