On Fri, Jul 21, 2023 at 12:30:10PM +0100, Daniel Golle wrote: > On Fri, Jul 21, 2023 at 01:11:40PM +0200, Greg Kroah-Hartman wrote: > > On Fri, Jul 21, 2023 at 11:40:51AM +0100, Daniel Golle wrote: > > > On Thu, Jul 20, 2023 at 11:31:06PM -0700, Christoph Hellwig wrote: > > > > On Thu, Jul 20, 2023 at 05:02:32PM +0100, Daniel Golle wrote: > > > > > On Thu, Jul 20, 2023 at 12:04:43AM -0700, Christoph Hellwig wrote: > > > > > > The layering here is exactly the wrong way around. This block device > > > > > > as nvmem provide has not business sitting in the block layer and being > > > > > > keyed ff the gendisk registration. Instead you should create a new > > > > > > nvmem backed that opens the block device as needed if it fits your > > > > > > OF description without any changes to the core block layer. > > > > > > > > > > > > > > > > Ok. I will use a class_interface instead. > > > > > > > > I'm not sure a class_interface makes much sense here. Why does the > > > > block layer even need to know about you using a device a nvmem provider? > > > > > > It doesn't. But it has to notify the nvmem providing driver about the > > > addition of new block devices. This is what I'm using class_interface > > > for, simply to hook into .add_dev of the block_class. > > > > Why is this single type of block device special to require this, yet all > > others do not? Encoding this into the block layer feels like a huge > > layering violation to me, why not do it how all other block drivers do > > it instead? > > I was thinkng of this as a generic solution in no way tied to one specific > type of block device. *Any* internal block device which can be used to > boot from should also be usable as NVMEM provider imho. Define "internal" :) And that's all up to the boot process in userspace, the kernel doesn't care about this. > > > > As far as I can tell your provider should layer entirely above the > > > > block layer and not have to be integrated with it. > > > > > > My approach using class_interface doesn't require any changes to be > > > made to existing block code. However, it does use block_class. If > > > you see any other good option to implement matching off and usage of > > > block devices by in-kernel users, please let me know. > > > > Do not use block_class, again, that should only be for the block core to > > touch. Individual block drivers should never be poking around in it. > > Do I have any other options to coldplug and be notified about newly > added block devices, so the block-device-consuming driver can know > about them? What other options do you need? > This is not a rhetoric question, I've been looking for other ways > and haven't found anything better than class_find_device or > class_interface. Never use that, sorry, that's not for a driver to touch. > Using those also prevents blk-nvmem to be built as > a module, so I'd really like to find alternatives. > E.g. for MTD we got struct mtd_notifier and register_mtd_user(). Your storage/hardware driver should be the thing that "finds block devices" and registers them with the block class core, right? After that, what matters? confused, greg k-h
