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? > > 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. thanks, greg k-h
