Hi Ulf, On Tue, Mar 12, 2024 at 01:22:49PM +0100, Ulf Hansson wrote: > On Tue, 5 Mar 2024 at 21:23, Daniel Golle <daniel@xxxxxxxxxxxxxx> wrote: > > > > On embedded devices using an eMMC it is common that one or more (hw/sw) > > partitions on the eMMC are used to store MAC addresses and Wi-Fi > > calibration EEPROM data. > > > > Implement an NVMEM provider backed by block devices as typically the > > NVMEM framework is used to have kernel drivers read and use binary data > > from EEPROMs, efuses, flash memory (MTD), ... > > > > In order to be able to reference hardware partitions on an eMMC, add code > > to bind each hardware partition to a specific firmware subnode. > > > > This series is meant to open the discussion on how exactly the device > > tree schema for block devices and partitions may look like, and even > > if using the block layer to back the NVMEM device is at all the way to > > go -- to me it seemed to be a good solution because it will be reuable > > e.g. for (normal, software GPT or MBR) partitions of an NVMe SSD. > > > > This series has previously been submitted on July 19th 2023[1] and most of > > the basic idea did not change since. > > > > However, the recent introduction of bdev_file_open_by_dev() allow to > > get rid of most use of block layer internals which supposedly was the > > main objection raised by Christoph Hellwig back then. > > > > Most of the other comments received for in the first RFC have also > > been addressed, however, what remains is the use of class_interface > > (lacking an alternative way to get notifications about addition or > > removal of block devices from the system). As this has been criticized > > in the past I'm specifically interested in suggestions on how to solve > > this in another way -- ideally without having to implement a whole new > > way for in-kernel notifications of appearing or disappearing block > > devices... > > > > And, in a way just like in case of MTD and UBI, I believe acting as an > > NVMEM provider *is* a functionality which belongs to the block layer > > itself and, other than e.g. filesystems, is inconvenient to implement > > elsewhere. > > I don't object to the above, however to keep things scalable at the > block device driver level, such as the MMC subsystem, I think we > should avoid having *any* knowledge about the binary format at these > kinds of lower levels. > > Even if most of the NVMEM format is managed elsewhere, the support for > NVMEM partitions seems to be dealt with from the MMC subsystem too. In an earlier iteration of this RFC it was requested to make NVMEM support opt-in (instead of opt-out for mtdblock and ubiblock, which already got their own NVMEM provider implementation). Hence at least a change to opt-in for NVMEM support is required in the MMC subsystem, together with making sure that MMC devices have their fwnode assigned. > Why can't NVMEM partitions be managed the usual way via the MBR/GPT? Absolutely, maybe my wording was not clear, but that's exactly what I'm suggesting here. There are no added parsers nor any knowledge about binary formats in this patchset. Or did I misunderstand your comment?
