linux-kernel - Re: [PATCH v2 1/2] mfd: mfd-core: Add mechanism for removal of a subset of children

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Date:   Tue, 16 Jun 2020 14:22:59 +0100
From:   Lee Jones <lee.jones@...aro.org>
To:     Charles Keepax <ckeepax@...nsource.cirrus.com>
Cc:     linux-kernel@...r.kernel.org, patches@...nsource.cirrus.com
Subject: Re: [PATCH v2 1/2] mfd: mfd-core: Add mechanism for removal of a
 subset of children

On Tue, 16 Jun 2020, Charles Keepax wrote:

> On Tue, Jun 16, 2020 at 10:15:45AM +0100, Lee Jones wrote:
> > On Tue, 16 Jun 2020, Charles Keepax wrote:
> > > On Tue, Jun 16, 2020 at 08:58:34AM +0100, Lee Jones wrote:
> > > > On Mon, 15 Jun 2020, Charles Keepax wrote:
> > > Does this match how you would expect this to be used?
> > 
> > No, not at all.
> > 
> > > I do have some concerns. The code can't use mfd_get_cell since it
> > > returns a const pointer, although the pointer in platform_device
> > > isn't const so we access that directly, could update mfd_get_cell? We
> > > also don't have access to mfd_dev_type outside of the mfd core so
> > > its hard to check we are actually setting the mfd_cell of actual
> > > MFD children, I guess just checking for mfd_cell being not NULL is
> > > good enough?
> > 
> > Hmmm... looks like I missed the fact that you needed additional
> > processing between the removal of each batch of devices.  My
> > implementation simply handles the order in which devices are removed
> > (a bit like initcall()s).
> > 
> > How about the inclusion of mfd_remove_devices_late(), whereby
> > mfd_remove_devices() will refuse to remove devices tagged with
> > MFD_DEP_LEVEL_HIGH.
> > 
> 
> Yeah this should work fine for my use-case.
> 
> > Not sure why, but I really dislike the idea of device removal by
> > arbitrary value/tag, as I see it spawning all sorts of weird and
> > wonderful implications/hacks/abuse.
> > 
> 
> Its definitely a spectrum with flexibility covering more
> use-cases but also definitely opening things up to more abuse. If
> you are more comfortable with this approach that is fine with me.
> 
> Would you like me to have a crack at coding it up this way? Or
> did you want to do a patch?

Either/or.  I don't want to steal your thunder, but I'm happy to draft
if you are.

-- 
Lee Jones [李琼斯]
Senior Technical Lead - Developer Services
Linaro.org │ Open source software for Arm SoCs
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