On Sun, 5 May 2024, Hans de Goede wrote:
> The Xiaomi [Mi]Pad 2 has 3 menu / home / back capacitive touch-buttons
> on its bottom bezel. These are backlit by LEDs attached to a TPS61158 LED
> controller which is controlled by the "pwm_soc_lpss_2" PWM output.
>
> Create a LED class device for this, using the new input-events trigger
> as default trigger so that the buttons automatically light up on any
> input activity.
>
> Note alternatively a "leds_pwm" platform device could be created together
> with the necessary fwnode_s_ and a fwnode link to the PWM controller.
> There are 2 downsides to this approach:
>
> 1. The code would still need to pwm_get() the PWM controller to get/attach
> a fwnode for the PWM controller fwnode link and setting up the necessary
> fwnodes is non trivial. So this would likely require more code then simply
non-trivial
> registering the LED class device directly.
>
> 2. Currently the leds_pwm driver and its devicetree bindings do not support
> limiting the maximum dutycycle to less then 100% which is required in this
> case (the leds_pwm driver can probably be extended to allow this).
Double space.
> Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx>
> ---
> .../platform/x86/x86-android-tablets/other.c | 44 +++++++++++++++++++
> 1 file changed, 44 insertions(+)
>
> diff --git a/drivers/platform/x86/x86-android-tablets/other.c b/drivers/platform/x86/x86-android-tablets/other.c
> index ff7b1d0abaa3..aa95645f3f24 100644
> --- a/drivers/platform/x86/x86-android-tablets/other.c
> +++ b/drivers/platform/x86/x86-android-tablets/other.c
> @@ -11,7 +11,9 @@
> #include <linux/acpi.h>
> #include <linux/gpio/machine.h>
> #include <linux/input.h>
> +#include <linux/leds.h>
> #include <linux/platform_device.h>
> +#include <linux/pwm.h>
>
> #include <dt-bindings/leds/common.h>
>
> @@ -662,8 +664,50 @@ static const struct software_node *ktd2026_node_group[] = {
> NULL
> };
>
> +/*
> + * For the LEDs which backlight the menu / home / back capacitive buttons on
> + * the bottom bezel. These are attached to a TPS61158 LED controller which
> + * is controlled by the "pwm_soc_lpss_2" PWM output.
> + */
> +#define XIAOMI_MIPAD2_LED_PERIOD_NS 19200
> +#define XIAOMI_MIPAD2_LED_MAX_DUTY 6000 /* From Android kernel */
> +
> +static struct pwm_device *xiaomi_mipad2_led_pwm;
> +
> +static int xiaomi_mipad2_brightness_set(struct led_classdev *led_cdev,
> + enum led_brightness val)
> +{
> + struct pwm_state state = {
> + .period = XIAOMI_MIPAD2_LED_PERIOD_NS,
> + .duty_cycle = val,
> + .enabled = !!val,
> + };
> +
> + return pwm_apply_might_sleep(xiaomi_mipad2_led_pwm, &state);
> +}
> +
> static int __init xiaomi_mipad2_init(struct device *dev)
> {
> + struct led_classdev *led_cdev;
> + int ret;
> +
> + xiaomi_mipad2_led_pwm = devm_pwm_get(dev, "pwm_soc_lpss_2");
> + if (IS_ERR(xiaomi_mipad2_led_pwm))
> + return dev_err_probe(dev, PTR_ERR(xiaomi_mipad2_led_pwm), "getting pwm\n");
> +
> + led_cdev = devm_kzalloc(dev, sizeof(*led_cdev), GFP_KERNEL);
> + if (!led_cdev)
> + return -ENOMEM;
> +
> + led_cdev->name = "mipad2:white:touch-buttons-backlight";
> + led_cdev->max_brightness = XIAOMI_MIPAD2_LED_MAX_DUTY;
> + led_cdev->brightness_set_blocking = xiaomi_mipad2_brightness_set;
> + led_cdev->default_trigger = "input-events";
> +
> + ret = devm_led_classdev_register(dev, led_cdev);
> + if (ret)
> + return dev_err_probe(dev, ret, "registering LED\n");
> +
> return software_node_register_node_group(ktd2026_node_group);
> }
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx>
--
i.
