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

[Bruno Pena]

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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