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 <[email protected]> > > 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 <[email protected]> > --- > 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 |
