From mboxrd@z Thu Jan 1 00:00:00 1970 Delivery-date: Tue, 02 Jun 2026 09:24:00 +0200 Received: from metis.whiteo.stw.pengutronix.de ([2a0a:edc0:2:b01:1d::104]) by lore.white.stw.pengutronix.de with esmtps (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.96) (envelope-from ) id 1wUJTk-001VSF-0Q for lore@lore.pengutronix.de; Tue, 02 Jun 2026 09:24:00 +0200 Received: from bombadil.infradead.org ([2607:7c80:54:3::133]) by metis.whiteo.stw.pengutronix.de with esmtp (Exim 4.92) (envelope-from ) id 1wUJTj-0001kj-9U for lore@pengutronix.de; Tue, 02 Jun 2026 09:24:00 +0200 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=QeCqEVL7AoLvF9GwN2oReiyQ530yjGsw+PNQ6GEnO6U=; b=R/gWA4pMTHmjDJyDXF3hxiCG0l ngyarfInaYhPwjsplcS5Sk+NeA1U564gflZiniGMZmXp0MWHC61P7JO2agxitdQfcxvhGBQFaKbdY 3DCWoDhGjQfA5tFjT7Y4Lhdh/zCixJhYTeZ3gzeb+xSr5ShGpjJ4B7MI6QSCeNr0Fvh9LPIa+YyGH rAf2fqCweuhheg+kCCW0aTl6azItGQfSSagMRDa9ugOG0fb6Y5twxfHyLaBN5ZmuR03KiFOcWNF2s w6WjT65RVwjYJKmptFIjTZj5kzrplsh9QVr/cHrjv+fybom0gGxuXcQXz/M2rLzJn4R4m3AsV1OkW qBqI7Krw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1wUJSg-0000000CTgB-1vZo; Tue, 02 Jun 2026 07:22:54 +0000 Received: from metis.whiteo.stw.pengutronix.de ([2a0a:edc0:2:b01:1d::104]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1wUJSd-0000000CTfa-3EgN for barebox@lists.infradead.org; Tue, 02 Jun 2026 07:22:53 +0000 Received: from ptz.office.stw.pengutronix.de ([2a0a:edc0:0:900:1d::77] helo=[127.0.0.1]) by metis.whiteo.stw.pengutronix.de with esmtp (Exim 4.92) (envelope-from ) id 1wUJSc-0001ZR-8L; Tue, 02 Jun 2026 09:22:50 +0200 Message-ID: Date: Tue, 2 Jun 2026 09:22:49 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird To: Johannes Schneider , barebox@lists.infradead.org Cc: thomas.haemmerle@leica-geosystems.com References: <20260602040953.1060278-1-johannes.schneider@leica-geosystems.com> <20260602040953.1060278-4-johannes.schneider@leica-geosystems.com> From: Ahmad Fatoum Content-Language: en-US, de-DE, de-BE In-Reply-To: <20260602040953.1060278-4-johannes.schneider@leica-geosystems.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260602_002251_837289_B7BA021D X-CRM114-Status: GOOD ( 23.09 ) X-BeenThere: barebox@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "barebox" X-SA-Exim-Connect-IP: 2607:7c80:54:3::133 X-SA-Exim-Mail-From: barebox-bounces+lore=pengutronix.de@lists.infradead.org X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on metis.whiteo.stw.pengutronix.de X-Spam-Level: X-Spam-Status: No, score=-5.2 required=4.0 tests=AWL,BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,RCVD_IN_DNSWL_MED,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.2 Subject: Re: [PATCH 3/6] video: backlight-pwm: make power-supply and enable-gpio optional X-SA-Exim-Version: 4.2.1 (built Wed, 08 May 2019 21:11:16 +0000) X-SA-Exim-Scanned: Yes (on metis.whiteo.stw.pengutronix.de) Hello, Thanks for your patch. It fixes a real bug, but I have some comments below. On 6/2/26 6:09 AM, Johannes Schneider wrote: > From: Thomas Haemmerle > > PWM backlight DT nodes for board displays often omit the power-supply regulator > (the rail is always-on) or use enable-gpios without a supply. The driver > previously treated both as mandatory and returned -ENODEV if either was absent, > blocking display initialisation on devices which use an always-on 3.3V supply > and no separate backlight enable regulator. > > Guard the regulator enable/disable calls with a NULL check, handle > -ENODEV from regulator_get() as "no supply present", and use GPIOD_ASIS > for enable GPIO so the initial pin state is not disturbed. > > Also improve the "Cannot find PWM device" error message to print the > actual error pointer so probe failures are diagnosable. > > Assisted-by: Claude:claude-sonnet-4-6 > Signed-of-by: Thomas Haemmerle > --- > drivers/video/backlight-pwm.c | 16 ++++++++++------ > drivers/video/backlight.c | 3 ++- > drivers/video/fsl-ldb.c | 2 +- > 3 files changed, 13 insertions(+), 8 deletions(-) > > diff --git a/drivers/video/backlight-pwm.c b/drivers/video/backlight-pwm.c > index d3c81114e0..9c8fcfbe93 100644 > --- a/drivers/video/backlight-pwm.c > +++ b/drivers/video/backlight-pwm.c > @@ -37,7 +37,8 @@ static int backlight_pwm_enable(struct pwm_backlight *pwm_backlight) > if (ret) > return ret; > > - regulator_enable(pwm_backlight->power); > + if (pwm_backlight->power) > + regulator_enable(pwm_backlight->power); Not needed, regulator_enable gracefully handles a NULL pointer. > > gpiod_direction_output(pwm_backlight->enable_gpio, true); > > @@ -55,7 +56,8 @@ static int backlight_pwm_disable(struct pwm_backlight *pwm_backlight) > > ret = gpiod_direction_output(pwm_backlight->enable_gpio, false); > if (!ret) { > - regulator_disable(pwm_backlight->power); > + if (pwm_backlight->power) > + regulator_disable(pwm_backlight->power); Likewise. > > /* > * Only disable PWM when an enable gpio is present. > @@ -148,7 +150,7 @@ static int pwm_backlight_parse_dt(struct device *dev, > pwm_backlight->backlight.brightness_max = pwm_backlight->scale; > } > > - pwm_backlight->enable_gpio = gpiod_get_optional(dev, "enable-gpios", 0); > + pwm_backlight->enable_gpio = gpiod_get_optional(dev, "enable", GPIOD_ASIS); While the commit message doesn't point it out, use of enable-gpios here is a bug. Fixes: 4c7238df6866 ("video: backlight-pwm: switch to gpiod functions") > > return 0; > } > @@ -161,7 +163,7 @@ static int backlight_pwm_of_probe(struct device *dev) > > pwm = of_pwm_request(dev->of_node, NULL); > if (IS_ERR(pwm)) { > - dev_err(dev, "Cannot find PWM device\n"); > + dev_err(dev, "Cannot find PWM device: %pe\n", pwm); > return PTR_ERR(pwm); return dev_errp_probe(dev, pwm, "Cannot find PWM device\n"); > } > > @@ -175,8 +177,10 @@ static int backlight_pwm_of_probe(struct device *dev) > > pwm_backlight->power = regulator_get(dev, "power"); regulator_get_optional() > if (IS_ERR(pwm_backlight->power)) { > - dev_err(dev, "Cannot find regulator\n"); > - return PTR_ERR(pwm_backlight->power); > + if (PTR_ERR(pwm_backlight->power) != -ENODEV) > + return dev_errp_probe(dev, pwm_backlight->power, > + "power supply\n"); > + pwm_backlight->power = NULL; > } > > pwm_backlight->backlight.slew_time_ms = 100; > diff --git a/drivers/video/backlight.c b/drivers/video/backlight.c > index 6d8146ee5a..bf7d40b59a 100644 > --- a/drivers/video/backlight.c > +++ b/drivers/video/backlight.c > @@ -94,8 +94,9 @@ int backlight_register(struct backlight_device *bl) > struct backlight_device *of_backlight_find(struct device_node *node) > { > struct backlight_device *bl; > + int ret; > > - of_device_ensure_probed(node); > + ret = of_device_ensure_probed(node); ret is never evaluated, so this change serves no purpose. It's also not needed, because the iteration below will either find a backlight or it won't find one. You can equally well just cast this to (void) here. > > class_for_each_container_of_device(&backlight_class, bl, dev) > if (bl->node == node) > diff --git a/drivers/video/fsl-ldb.c b/drivers/video/fsl-ldb.c > index 0ab720032c..09804ac329 100644 > --- a/drivers/video/fsl-ldb.c > +++ b/drivers/video/fsl-ldb.c > @@ -287,7 +287,7 @@ static int fsl_ldb_probe(struct device *dev) > > /* Only DRM_LVDS_DUAL_LINK_ODD_EVEN_PIXELS is supported */ > > - dev_info(dev, "LVDS channel pixel swap not supported.\n"); > + dev_dbg(dev, "LVDS channel pixel swap not supported.\n"); Cheers, Ahmad > > fsl_ldb->vpl.node = dev->of_node; > fsl_ldb->vpl.ioctl = &fsl_ldb_ioctl; -- Pengutronix e.K. | | Steuerwalder Str. 21 | http://www.pengutronix.de/ | 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |