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Date:   Fri, 21 Jul 2023 11:40:51 +0100
From:   Daniel Golle <daniel@makrotopia.org>
To:     Christoph Hellwig <hch@infradead.org>
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Subject: Re: [RFC PATCH 6/6] block: implement NVMEM provider
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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.

> 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.