Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Mon, 3 Apr 2023 11:09:14 +0200
From:   Marek =?UTF-8?B?QmVow7pu?= <kabel@kernel.org>
To:     "H. Nikolaus Schaller" <hns@goldelico.com>
Cc:     Pavel Machek <pavel@ucw.cz>, Lee Jones <lee@kernel.org>,
        linux-leds@vger.kernel.org, linux-kernel@vger.kernel.org,
        letux-kernel@openphoenux.org, NeilBrown <neilb@suse.de>,
        Linus Walleij <linus.walleij@linaro.org>
Subject: Re: [PATCH] leds: tca6507: fix error handling of using
 fwnode_property_read_string
Message-ID: <20230403110914.6106602e@dellmb>
In-Reply-To: <cbae7617db83113de726fcc423a805ebaa1bfca6.1680433978.git.hns@goldelico.com>
References: <cbae7617db83113de726fcc423a805ebaa1bfca6.1680433978.git.hns@goldelico.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: quoted-printable
Precedence: bulk

On Sun,  2 Apr 2023 13:12:59 +0200
"H. Nikolaus Schaller" <hns@goldelico.com> wrote:

> Commit 96f524105b9c ("leds: tca6507: use fwnode API instead of OF")
>=20
> changed to fwnode API but did not take into account that a missing proper=
ty
> "linux,default-trigger" now seems to return an error and as a side effect
> sets value to -1. This seems to be different from of_get_property() which
> always returned NULL in any case of error.
>=20
> Neglecting this side-effect leads to
>=20
> [   11.201965] Unable to handle kernel paging request at virtual address =
ffffffff when read
>=20
> in the strcmp() of led_trigger_set_default() if there is no led-trigger
> defined in the DTS.
>=20
> I don't know if this was recently introduced somewhere in the fwnode lib
> or if the effect was missed in initial testing. Anyways it seems to be a
> bug to ignore the error return value of an optional value here in the
> driver.
>=20
> Fixes: 96f524105b9c ("leds: tca6507: use fwnode API instead of OF")
> Cc: Marek Beh=C3=BAn <kabel@kernel.org>
> Cc: NeilBrown <neilb@suse.de>
> Cc: Linus Walleij <linus.walleij@linaro.org>
> Signed-off-by: H. Nikolaus Schaller <hns@goldelico.com>
> ---
>  drivers/leds/leds-tca6507.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
>=20
> diff --git a/drivers/leds/leds-tca6507.c b/drivers/leds/leds-tca6507.c
> index 07dd12686a696..634cabd5bb796 100644
> --- a/drivers/leds/leds-tca6507.c
> +++ b/drivers/leds/leds-tca6507.c
> @@ -691,8 +691,9 @@ tca6507_led_dt_init(struct device *dev)
>  		if (fwnode_property_read_string(child, "label", &led.name))
>  			led.name =3D fwnode_get_name(child);
> =20
> -		fwnode_property_read_string(child, "linux,default-trigger",
> -					    &led.default_trigger);
> +		if (fwnode_property_read_string(child, "linux,default-trigger",
> +						&led.default_trigger))
> +			led.default_trigger =3D NULL;
> =20
>  		led.flags =3D 0;
>  		if (fwnode_device_is_compatible(child, "gpio"))

Reviewed-by: Marek Beh=C3=BAn <kabel@kernel.org>