Re: About devm_platform_ioremap_resource [Was: Re: [PATCH 01/32] pwm: sun4i: convert to devm_platform_ioremap_resource]

From: Bartosz Golaszewski <bgolaszewski@baylibre.com>
To: "Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>
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Subject: Re: About devm_platform_ioremap_resource [Was: Re: [PATCH 01/32] pwm: sun4i: convert to devm_platform_ioremap_resource]
Date: Fri, 13 Nov 2020 10:12:46 +0100	[thread overview]
Message-ID: <CAMpxmJXWqKwhNxgY7CKG6ZvszWLxrVo-JCy4riWoXN8y+bCLUA@mail.gmail.com> (raw)
In-Reply-To: <20201113070343.lhcsbyvi5baxn3lq@pengutronix.de>

On Fri, Nov 13, 2020 at 8:04 AM Uwe Kleine-König
<u.kleine-koenig@pengutronix.de> wrote:
>
> Hello,
>
> [Added lkml and the people involved in commit 7945f929f1a7
> ("drivers: provide devm_platform_ioremap_resource()") to Cc:. For the
> new readers: This is about patches making use of
> devm_platform_ioremap_resource() instead of open coding it. Full context
> at https://lore.kernel.org/r/20201112190649.GA908613@ulmo]
>
> On Thu, Nov 12, 2020 at 10:14:29PM +0100, Uwe Kleine-König wrote:
> > On Thu, Nov 12, 2020 at 08:06:49PM +0100, Thierry Reding wrote:
> > > I also think that it's overly narrow is scope, so you can't actually
> > > "blindly" use this helper and I've seen quite a few cases where this was
> > > unknowingly used for cases where it shouldn't have been used and then
> > > broke things (because some drivers must not do the request_mem_region()
> > > for example).
> >
> > You have a link to such an accident?
>
> I got a hint in private here: https://lore.kernel.org/r/1555670144-24220-1-git-send-email-aisheng.dong@nxp.com
>
> devm_platform_ioremap_resource() is platform_get_resource() +
> devm_ioremap_resource() and here it was used to replace
> platform_get_resource() + devm_ioremap().
>
> IMHO the unlucky thing in this situation is that devm_ioremap_resource()
> and devm_ioremap() are different by more than just how they get the area
> to remap. (i.e. devm_ioremap_resource() also does
> devm_request_mem_region().)
>
> So the problem is not the added wrapper, but unclear semantics in the
> functions it uses. In my eyes devm_ioremap() and
> devm_platform_ioremap_resource() should better be named
> devm_request_ioremap() and devm_platform_request_ioremap_resource()
> respectively. Is it worth to rename these for clearity?

But devm_ioremap() doesn't request the region. Did you mean
devm_ioremap_resource() should become devm_request_ioremap_resource()?

Bartosz

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