linux-kernel - Re: [PATCH v2-UPDATE2 3/4] resource: Add device-managed insert/remove

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Date:	Tue, 08 Mar 2016 17:04:04 -0700
From:	Toshi Kani <toshi.kani@....com>
To:	Dan Williams <dan.j.williams@...el.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Ingo Molnar <mingo@...nel.org>, Borislav Petkov <bp@...e.de>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>,
	Linux ACPI <linux-acpi@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2-UPDATE2 3/4] resource: Add device-managed
 insert/remove_resource()

On Tue, 2016-03-08 at 14:44 -0800, Dan Williams wrote:
> On Tue, Mar 8, 2016 at 2:23 PM, Linus Torvalds
> <torvalds@...ux-foundation.org> wrote:
> > On Tue, Mar 8, 2016 at 12:59 PM, Dan Williams <dan.j.williams@...el.com
> > > wrote:
> > > 
> > > Here's the usage patch from Toshi [1] (copied below).  It is indeed a
> > > resource injected by nfit / nvdimm bus implementation.  We just
> > > happen
> > > to support nfit and libnvdimm as modules.
> > > 
> > > The goal of these patches is to use the ACPI NFIT data to create a
> > > "Persistent Memory" rather than "reserved" resource.  This is for
> > > platform-firmware implementations that use E820-Type2 rather than
> > > E820-Type7 to describe pmem.
> > 
> > So my worry is that there is likely exactly one or two of these kinds
> > of sites.
> > 
> > Why couldn't they just use insert_resource() and then remove it
> > manually?
> 
> You mean instead of introducing a devm_insert_resource() as a helpful
> first-class-citizen api, just arrange for the resource to be inserted
> locally?  Sure.
> 
> I assume Toshi was looking to keep the devm semantics like the rest of
> the nfit driver, but we can do that locally with devm_add_action() and
> skip the new general purpose api.

Yes, I prefer the devm semantics.  insert_resource() and remove_resource()
are not exported interfaces.  So, with devm_add_action(), we still need to
introduce built-in exported wrappers for insert/remove_resource(), unless
we change to export them directly.  Since we need to export "something", I
think it is better to export their devm interfaces.

Thanks,
-Toshi