On Tue, Jan 20, 2026 at 10:22:02AM +0530, [email protected] wrote: > > > On 14-01-2026 21:33, Daniel Thompson wrote: > > On Tue, Jan 13, 2026 at 12:47:26PM +0530, [email protected] wrote: > >> > >> > >> On 05-01-2026 15:39, Daniel Thompson wrote: > >>> On Mon, Jan 05, 2026 at 02:21:20PM +0530, Sudarshan Shetty wrote: > >>>> Extend the gpio-backlight driver to handle multiple GPIOs instead of a > >>>> single one. This allows panels that require driving several enable pins > >>>> to be controlled by the backlight framework. > >>>> > >>>> Signed-off-by: Sudarshan Shetty <[email protected]> > >>>> --- > >>>> drivers/video/backlight/gpio_backlight.c | 61 +++++++++++++++++------- > >>>> 1 file changed, 45 insertions(+), 16 deletions(-) > >>>> > >>>> diff --git a/drivers/video/backlight/gpio_backlight.c > >>>> b/drivers/video/backlight/gpio_backlight.c > >>>> index 728a546904b0..037e1c111e48 100644 > >>>> --- a/drivers/video/backlight/gpio_backlight.c > >>>> +++ b/drivers/video/backlight/gpio_backlight.c > >>>> @@ -17,14 +17,18 @@ > >>>> > >>>> struct gpio_backlight { > >>>> struct device *dev; > >>>> - struct gpio_desc *gpiod; > >>>> + struct gpio_desc **gpiods; > >>>> + unsigned int num_gpios; > >>> > >>> Why not use struct gpio_descs for this? > >>> > >>> Once you do that, then most of the gbl->num_gpios loops can be replaced > >>> with > >>> calls to the array based accessors. > >>> > >> > >> Based on your feedback, I have updated the implementation to use > >> struct gpio_descs and array-based accessors, as recommended like > >> below: > >> > >> git diff drivers/video/backlight/gpio_backlight.c > >> diff --git a/drivers/video/backlight/gpio_backlight.c > >> b/drivers/video/backlight/gpio_backlight.c > >> index 037e1c111e48..e99d7a9dc670 100644 > >> --- a/drivers/video/backlight/gpio_backlight.c > >> +++ b/drivers/video/backlight/gpio_backlight.c > >> @@ -14,22 +14,37 @@ > >> #include <linux/platform_device.h> > >> #include <linux/property.h> > >> #include <linux/slab.h> > >> +#include <linux/bitmap.h> > >> > >> struct gpio_backlight { > >> struct device *dev; > >> - struct gpio_desc **gpiods; > >> + struct gpio_descs *gpiods; > >> unsigned int num_gpios; > >> }; > >> > >> static int gpio_backlight_update_status(struct backlight_device *bl) > >> { > >> struct gpio_backlight *gbl = bl_get_data(bl); > >> - unsigned int i; > >> + unsigned int n = gbl->num_gpios; > >> int br = backlight_get_brightness(bl); > >> + unsigned long *value_bitmap; > >> + int words = BITS_TO_LONGS(n); > >> + > >> + value_bitmap = kcalloc(words, sizeof(unsigned long), GFP_KERNEL); > > > > Not sure you need a kcalloc() here. If you want to support more than 32 > > GPIOs then you can pre-allocate space with a devm_kcalloc() in the probe > > method rather than reallocate every time it is used. > > > > To be honest I don't really mind putting a hard limit on the maximum > > gpl->num_gpios (so you can just use a local variable) and having no > > allocation at all. > > > > Thanks for the suggestion. I addressed the kcalloc() concern by > moving the bitmap allocation to probe using devm_kcalloc() as > below: > > diff --git a/drivers/video/backlight/gpio_backlight.c > b/drivers/video/backlight/gpio_backlight.c > index 0eb42d8bf1d9..7af5dc4f0315 100644 > --- a/drivers/video/backlight/gpio_backlight.c > +++ b/drivers/video/backlight/gpio_backlight.c > @@ -19,32 +19,25 @@ > struct gpio_backlight { > struct device *dev; > struct gpio_descs *gpiods; > - unsigned int num_gpios; > + unsigned long *bitmap; > }; > > static int gpio_backlight_update_status(struct backlight_device *bl) > { > struct gpio_backlight *gbl = bl_get_data(bl); > - unsigned int n = gbl->num_gpios; > + unsigned int n = gbl->gpiods->ndescs; > int br = backlight_get_brightness(bl); > - unsigned long *value_bitmap; > - int words = BITS_TO_LONGS(n); > - > - value_bitmap = kcalloc(words, sizeof(unsigned long), GFP_KERNEL); > - if (!value_bitmap) > - return -ENOMEM; > > if (br) > - bitmap_fill(value_bitmap, n); > + bitmap_fill(gbl->bitmap, n); > else > - bitmap_zero(value_bitmap, n); > + bitmap_zero(gbl->bitmap, n); > > - gpiod_set_array_value_cansleep(gbl->gpiods->ndescs, > + gpiod_set_array_value_cansleep(n, > gbl->gpiods->desc, > gbl->gpiods->info, > - value_bitmap); > + gbl->bitmap); > > - kfree(value_bitmap); > return 0; > } > > @@ -67,22 +60,25 @@ static int gpio_backlight_probe(struct platform_device > *pdev) > struct device *dev = &pdev->dev; > struct gpio_backlight_platform_data *pdata = dev_get_platdata(dev); > struct device_node *of_node = dev->of_node; > - struct backlight_properties props; > + struct backlight_properties props = { }; > struct backlight_device *bl; > struct gpio_backlight *gbl; > - int ret, init_brightness, def_value; > - unsigned int i; > + bool def_value; > + enum gpiod_flags flags; > + unsigned int n; > + int words; > > - gbl = devm_kzalloc(dev, sizeof(*gbl), GFP_KERNEL); > - if (gbl == NULL) > + gbl = devm_kcalloc(dev, 1, sizeof(*gbl), GFP_KERNEL); > + if (!gbl) > return -ENOMEM; > > if (pdata) > gbl->dev = pdata->dev; > > def_value = device_property_read_bool(dev, "default-on"); > - > - gbl->gpiods = devm_gpiod_get_array(dev, NULL, GPIOD_ASIS); > + flags = def_value ? GPIOD_OUT_HIGH : GPIOD_OUT_LOW; > + > + gbl->gpiods = devm_gpiod_get_array(dev, NULL, flags); > if (IS_ERR(gbl->gpiods)) { > if (PTR_ERR(gbl->gpiods) == -ENODEV) > return dev_err_probe(dev, -EINVAL, > @@ -90,12 +86,17 @@ static int gpio_backlight_probe(struct platform_device > *pdev) > return PTR_ERR(gbl->gpiods); > } > > - gbl->num_gpios = gbl->gpiods->ndescs; > - if (gbl->num_gpios == 0) > + n = gbl->gpiods->ndescs; > + if (!n) > return dev_err_probe(dev, -EINVAL, > - "The gpios parameter is missing or invalid\n"); > + "No GPIOs provided\n"); > + > + words = BITS_TO_LONGS(n); > + gbl->bitmap = devm_kcalloc(dev, words, sizeof(unsigned long), > + GFP_KERNEL); > + if (!gbl->bitmap) > + return -ENOMEM; > > - memset(&props, 0, sizeof(props)); > props.type = BACKLIGHT_RAW; > props.max_brightness = 1; > bl = devm_backlight_device_register(dev, dev_name(dev), dev, gbl, > @@ -106,50 +107,19 @@ static int gpio_backlight_probe(struct platform_device > *pdev) > } > > /* Set the initial power state */ > - if (!of_node || !of_node->phandle) { > + if (!of_node || !of_node->phandle) > /* Not booted with device tree or no phandle link to the node > */ > bl->props.power = def_value ? BACKLIGHT_POWER_ON > : BACKLIGHT_POWER_OFF; > - } else { > - bool all_high = true; > - unsigned long *value_bitmap; > - int words = BITS_TO_LONGS(gbl->num_gpios); > - > - value_bitmap = kcalloc(words, sizeof(unsigned long), > - GFP_KERNEL); > - if (!value_bitmap) > - return -ENOMEM; > - > - ret = gpiod_get_array_value_cansleep(gbl->gpiods->ndescs, > - gbl->gpiods->desc, > - gbl->gpiods->info, > - value_bitmap); > - if (ret) { > - kfree(value_bitmap); > - return dev_err_probe(dev, ret, > - "failed to read initial gpio values\n"); > - } > - > - all_high = bitmap_full(value_bitmap, gbl->num_gpios); > - > - kfree(value_bitmap); > - bl->props.power = > - all_high ? BACKLIGHT_POWER_ON : BACKLIGHT_POWER_OFF; > - } > - > - bl->props.brightness = 1; > - > - init_brightness = backlight_get_brightness(bl); > + else if (gpiod_get_value_cansleep(gbl->gpiods->desc[0]) == 0) > + bl->props.power = BACKLIGHT_POWER_OFF; > + else > + bl->props.power = BACKLIGHT_POWER_ON; > > - for (i = 0; i < gbl->num_gpios; i++) { > - ret = gpiod_direction_output(gbl->gpiods->desc[i], > - init_brightness); > - if (ret) > - return dev_err_probe(dev, ret, > - "failed to set gpio %u direction\n", > - i); > - } > + bl->props.brightness = def_value ? 1 : 0; > > + gpio_backlight_update_status(bl); > + > platform_set_drvdata(pdev, bl); > return 0; > } > > Kindly confirm whether this approach aligns with your > expectations.
As mentioned yesterday, I'd rather just review a v2 patch than this kind of meta-patch. Please send a v2 patch instead. Daniel.
