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 <[email protected]> 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 <[email protected]> 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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