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

[Bruno Pena]

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
>>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.infradead.org/pipermail/openwrt-devel/attachments/20200122/3d9b43af/attachment.htm>
-------------- next part --------------
_______________________________________________
openwrt-devel mailing list
openwrt-devel at lists.openwrt.org
https://lists.openwrt.org/mailman/listinfo/openwrt-devel