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[2003:e4:1f20:1d00:f22f:74ff:fe1f:3a53]) by smtp.gmail.com with ESMTPSA id ez23-20020a1709070bd700b00780a26edfcesm2324189ejc.60.2022.09.28.05.55.51 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 28 Sep 2022 05:55:51 -0700 (PDT) Date: Wed, 28 Sep 2022 14:55:49 +0200 From: Thierry Reding To: Uwe =?utf-8?Q?Kleine-K=C3=B6nig?= Cc: linux-pwm@vger.kernel.org, kernel@pengutronix.de, Steven Rostedt , Ingo Molnar , Pavel Machek , Douglas Anderson , Andrzej Hajda , Neil Armstrong , Robert Foss , Laurent Pinchart , Jonas Karlman , Jernej Skrabec , Linus Walleij , Bartosz Golaszewski , linux-leds@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-gpio@vger.kernel.org Subject: Re: [PATCH 3/3] pwm: Handle .get_state() failures Message-ID: References: <20220916151506.298488-1-u.kleine-koenig@pengutronix.de> <20220916151506.298488-3-u.kleine-koenig@pengutronix.de> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="e50AYHBveDjKXIgT" Content-Disposition: inline In-Reply-To: <20220916151506.298488-3-u.kleine-koenig@pengutronix.de> User-Agent: Mutt/2.2.7 (2022-08-07) Precedence: bulk List-ID: X-Mailing-List: linux-gpio@vger.kernel.org --e50AYHBveDjKXIgT Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Fri, Sep 16, 2022 at 05:15:06PM +0200, Uwe Kleine-K=C3=B6nig wrote: > This suppresses diagnosis for PWM_DEBUG routines and makes sure that > pwm->state isn't modified in pwm_device_request() if .get_state() fails. >=20 > Signed-off-by: Uwe Kleine-K=C3=B6nig > --- > drivers/pwm/core.c | 12 +++++++++++- > 1 file changed, 11 insertions(+), 1 deletion(-) >=20 > diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c > index 381db04cfa00..421573590613 100644 > --- a/drivers/pwm/core.c > +++ b/drivers/pwm/core.c > @@ -108,9 +108,14 @@ static int pwm_device_request(struct pwm_device *pwm= , const char *label) > } > =20 > if (pwm->chip->ops->get_state) { > - err =3D pwm->chip->ops->get_state(pwm->chip, pwm, &pwm->state); > + struct pwm_state state; > + > + err =3D pwm->chip->ops->get_state(pwm->chip, pwm, &state); > trace_pwm_get(pwm, &pwm->state, err); > =20 > + if (!err) > + pwm->state =3D state; So basically this means that callers of pwm_get_state() will get the zeroed out pwm->state. This can cause issues with the likes of pwm_set_relative_duty_cycle() which many drivers would use. Do we perhaps want to set an internal error in this case so that it can be propagated to callers in pwm_get_state()? That would allow them to fall back to some default configuration rather than potentially breaking altogether. 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