Re: [PATCH v8 6/8] nvmem: core: Rework layouts to become platform devices

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Mon, Aug 07, 2023 at 10:24:17AM +0200, Miquel Raynal wrote:
> Current layout support was initially written without modules support in
> mind. When the requirement for module support rose, the existing base
> was improved to adopt modularization support, but kind of a design flaw
> was introduced. With the existing implementation, when a storage device
> registers into NVMEM, the core tries to hook a layout (if any) and
> populates its cells immediately. This means, if the hardware description
> expects a layout to be hooked up, but no driver was provided for that,
> the storage medium will fail to probe and try later from
> scratch. Technically, the layouts are more like a "plus" and, even we
> consider that the hardware description shall be correct, we could still
> probe the storage device (especially if it contains the rootfs).
> 
> One way to overcome this situation is to consider the layouts as
> devices, and leverage the existing notifier mechanism. When a new NVMEM
> device is registered, we can:
> - populate its nvmem-layout child, if any
> - try to modprobe the relevant driver, if relevant
> - try to hook the NVMEM device with a layout in the notifier
> And when a new layout is registered:
> - try to hook all the existing NVMEM devices which are not yet hooked to
>   a layout with the new layout
> This way, there is no strong order to enforce, any NVMEM device creation
> or NVMEM layout driver insertion will be observed as a new event which
> may lead to the creation of additional cells, without disturbing the
> probes with costly (and sometimes endless) deferrals.

This is good, but why are you using a platform device here?  Is it a
real platform device, or just a "fake" one you created?  If a fake one,
please don't do that, use a real device, or a virtual device.  Platform
devices should ONLY represent actual, real, platform devices (i.e. ones
descibed by the firmware).

Sorry but I couldn't answer this question by looking at this patch, the
device creation path isn't exactly obvious :)

thanks,

greg k-h