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Thu, 19 Aug 2021 06:28:32 -0700 (PDT) Date: Thu, 19 Aug 2021 15:28:31 +0200 From: Thierry Reding To: Uwe =?utf-8?Q?Kleine-K=C3=B6nig?= Cc: Lee Jones , linux-pwm@vger.kernel.org, kernel@pengutronix.de, Geert Uytterhoeven Subject: Re: [PATCH 3/3] pwm: Restore initial state if a legacy callback fails Message-ID: References: <20210701072927.328254-1-u.kleine-koenig@pengutronix.de> <20210701072927.328254-4-u.kleine-koenig@pengutronix.de> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="NFDDAHIHqC+jbcN4" Content-Disposition: inline In-Reply-To: <20210701072927.328254-4-u.kleine-koenig@pengutronix.de> User-Agent: Mutt/2.1.1 (e2a89abc) (2021-07-12) Precedence: bulk List-ID: X-Mailing-List: linux-pwm@vger.kernel.org --NFDDAHIHqC+jbcN4 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Thu, Jul 01, 2021 at 09:29:27AM +0200, Uwe Kleine-K=C3=B6nig wrote: > It is not entirely accurate to go back to the initial state after e.g. > .enable() failed, as .config() still modified the hardware, but this same > inconsistency exists for drivers that implement .apply(). >=20 > Signed-off-by: Uwe Kleine-K=C3=B6nig > --- > drivers/pwm/core.c | 14 ++++++++------ > 1 file changed, 8 insertions(+), 6 deletions(-) >=20 > diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c > index 20afe6d0bc5e..6e30ef9b9b79 100644 > --- a/drivers/pwm/core.c > +++ b/drivers/pwm/core.c > @@ -539,10 +539,8 @@ static int pwm_apply_legacy(struct pwm_chip *chip, s= truct pwm_device *pwm, > const struct pwm_state *state) > { > int err; > + struct pwm_state initial_state =3D pwm->state; > =20 > - /* > - * FIXME: restore the initial state in case of error. > - */ > if (state->polarity !=3D pwm->state.polarity) { > if (!chip->ops->set_polarity) > return -EINVAL; > @@ -563,7 +561,7 @@ static int pwm_apply_legacy(struct pwm_chip *chip, st= ruct pwm_device *pwm, > =20 > err =3D chip->ops->set_polarity(chip, pwm, state->polarity); > if (err) > - return err; > + goto rollback; > =20 > pwm->state.polarity =3D state->polarity; > } > @@ -586,7 +584,7 @@ static int pwm_apply_legacy(struct pwm_chip *chip, st= ruct pwm_device *pwm, > state->duty_cycle, > state->period); > if (err) > - return err; > + goto rollback; > =20 > pwm->state.period =3D state->period; > pwm->state.duty_cycle =3D state->duty_cycle; > @@ -594,10 +592,14 @@ static int pwm_apply_legacy(struct pwm_chip *chip, = struct pwm_device *pwm, > if (!pwm->state.enabled) { > err =3D chip->ops->enable(chip, pwm); > if (err) > - return err; > + goto rollback; > } > =20 > return 0; > + > +rollback: > + pwm->state =3D initial_state; > + return err; > } Can't we achieve the same thing by just removing all the updates to pwm->state in pwm_apply_legacy()? Patch 1 in the series now does pwm->state =3D *state for both the atomic and the legacy cases, so if we don't update pwm->state explicitly in pwm_apply_legacy(), then there should be no need to rollback, right? What we currently do is a bit redundant anyway. pwm->state =3D *state should be a no-op after pwm_apply_legacy(). 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