Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Fri, 13 Nov 2020 08:03:43 +0100
From:   Uwe =?utf-8?Q?Kleine-K=C3=B6nig?= <u.kleine-koenig@pengutronix.de>
To:     Thierry Reding <thierry.reding@gmail.com>
Cc:     alexandre.belloni@bootlin.com, heiko@sntech.de,
        Yangtao Li <tiny.windzz@gmail.com>,
        nicolas.ferre@microchip.com, matthias.bgg@gmail.com,
        linux-riscv@lists.infradead.org, festevam@gmail.com,
        f.fainelli@gmail.com, shc_work@mail.ru, khilman@baylibre.com,
        ludovic.desroches@microchip.com, jonathanh@nvidia.com,
        linux-rockchip@lists.infradead.org, wens@csie.org,
        bcm-kernel-feedback-list@broadcom.com, linux-imx@nxp.com,
        slemieux.tyco@gmail.com, linux-pwm@vger.kernel.org,
        rjui@broadcom.com, s.hauer@pengutronix.de, mripard@kernel.org,
        vz@mleia.com, linux-mediatek@lists.infradead.org,
        linux-rpi-kernel@lists.infradead.org, paul.walmsley@sifive.com,
        linux-tegra@vger.kernel.org, linux-amlogic@lists.infradead.org,
        Lee Jones <lee.jones@linaro.org>,
        linux-arm-kernel@lists.infradead.org, sbranden@broadcom.com,
        linux-kernel@vger.kernel.org, palmer@dabbelt.com,
        kernel@pengutronix.de, shawnguo@kernel.org,
        claudiu.beznea@microchip.com, nsaenzjulienne@suse.de,
        Bartosz Golaszewski <bgolaszewski@baylibre.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        Linus Walleij <linus.walleij@linaro.org>
Subject: About devm_platform_ioremap_resource [Was: Re: [PATCH 01/32] pwm:
 sun4i: convert to devm_platform_ioremap_resource]
Message-ID: <20201113070343.lhcsbyvi5baxn3lq@pengutronix.de>
References: <20191229080610.7597-1-tiny.windzz@gmail.com>
 <20201112161346.gp5nenuagx5wmwl2@pengutronix.de>
 <20201112190649.GA908613@ulmo>
 <20201112211429.kfyqzkmmchjo6pll@pengutronix.de>
MIME-Version: 1.0
Content-Type: multipart/signed; micalg=pgp-sha512;
        protocol="application/pgp-signature"; boundary="bfm7upvbg2x7q3rm"
Content-Disposition: inline
In-Reply-To: <20201112211429.kfyqzkmmchjo6pll@pengutronix.de>
Precedence: bulk


--bfm7upvbg2x7q3rm
Content-Type: text/plain; charset=iso-8859-1
Content-Disposition: inline
Content-Transfer-Encoding: quoted-printable

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-K=F6nig 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).
>=20
> 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?

Best regards
Uwe

--=20
Pengutronix e.K.                           | Uwe Kleine-K=F6nig            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

--bfm7upvbg2x7q3rm
Content-Type: application/pgp-signature; name="signature.asc"

-----BEGIN PGP SIGNATURE-----

iQEzBAABCgAdFiEEfnIqFpAYrP8+dKQLwfwUeK3K7AkFAl+uL8wACgkQwfwUeK3K
7AmhFQf/UMY3Z/O4ajFXsCh5aeqAW1EKy0wv+YtVLmLASYlkvBQ5OpoaFH6U7oZY
a1BVjZ2I3q3pi1zMs+2dPAkylNi0VEIERvwncqHOfYN4FjdNsI85rKbxu4DNsWHJ
wlaQxLwmUmDXDESpJ4RN8JqF/V/nPZfj/4V52ANK31PZ+i4fYnIlW6TU0cJwoJ9s
aGSM2QwTb27uaRg5hqZqfOyIkt3wwkDJIF65H/vi64r0Gtm3c+0iKbEmlXr2XZCh
APhFgQQDGFOMXdSBZeFxTtuLCzuG/RA3Fxb+7okleZUL6GrSwq7xWHJGorO136kq
mo88jw2ceYf/qJA9E4atasOfbQUtlg==
=gJ1m
-----END PGP SIGNATURE-----

--bfm7upvbg2x7q3rm--