Re: [PATCH v3 5/5] platform/chrome: cros_kbd_led_backlight: support EC PWM backend

Matthias Kaehlcke
2022-05-19T22:40:31Z

On Mon, Mar 21, 2022 at 04:55:47PM +0800, Tzung-Bi Shih wrote:
> EC PWM backend uses EC_CMD_PWM_SET_KEYBOARD_BACKLIGHT and
> EC_CMD_PWM_GET_KEYBOARD_BACKLIGHT for setting and getting the brightness
> respectively.
>
> Signed-off-by: Tzung-Bi Shih <tzungbi@kernel.org>
> ---
> Changes from v2:
> - Turn CROS_KBD_LED_BACKLIGHT_EC_PWM to boolean.
> - Use #ifdef for boolean CROS_KBD_LED_BACKLIGHT_EC_PWM.
>
> Changes from v1:
> - Update email address accordingly.
>
> drivers/platform/chrome/Kconfig | 6 +
> .../platform/chrome/cros_kbd_led_backlight.c | 126 +++++++++++++++---
> 2 files changed, 117 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/platform/chrome/Kconfig b/drivers/platform/chrome/Kconfig
> index 3f74679a556c..e02789d7c0d4 100644
> --- a/drivers/platform/chrome/Kconfig
> +++ b/drivers/platform/chrome/Kconfig
> @@ -142,6 +142,12 @@ config CROS_KBD_LED_BACKLIGHT_ACPI
> help
> ChromeOS keyboard backlight ACPI backend.
>
> +config CROS_KBD_LED_BACKLIGHT_EC_PWM
> + bool "ChromeOS keyboard backlight EC PWM backend"
> + depends on CROS_EC && CROS_KBD_LED_BACKLIGHT
> + help
> + ChromeOS keyboard backlight EC PWM backend.
> +
> config CROS_EC_CHARDEV
> tristate "ChromeOS EC miscdevice"
> depends on MFD_CROS_EC_DEV
> diff --git a/drivers/platform/chrome/cros_kbd_led_backlight.c b/drivers/platform/chrome/cros_kbd_led_backlight.c
> index 5cbe27cb4610..8c35dd2fa607 100644
> --- a/drivers/platform/chrome/cros_kbd_led_backlight.c
> +++ b/drivers/platform/chrome/cros_kbd_led_backlight.c
> @@ -11,10 +11,17 @@
> #include <linux/leds.h>
> #include <linux/module.h>
> #include <linux/of.h>
> +#include <linux/platform_data/cros_ec_commands.h>
> +#include <linux/platform_data/cros_ec_proto.h>
> #include <linux/platform_device.h>
> #include <linux/property.h>
> #include <linux/slab.h>
>
> +struct keyboard_led_private {

Why 'private', isn't this more a 'cros_ec_kdb_bl' or similar?

> + struct led_classdev cdev;
> + struct cros_ec_device *ec;
> +};
> +
> /**
> * struct keyboard_led_drvdata - keyboard LED driver data.
> * @init: Init function.
> @@ -40,6 +47,8 @@ struct keyboard_led_drvdata {
> enum led_brightness max_brightness;
> };
>
> +#define KEYBOARD_BACKLIGHT_MAX 100
> +
> #ifdef CONFIG_CROS_KBD_LED_BACKLIGHT_ACPI
>
> /* Keyboard LED ACPI Device must be defined in firmware */
> @@ -47,8 +56,6 @@ struct keyboard_led_drvdata {
> #define ACPI_KEYBOARD_BACKLIGHT_READ ACPI_KEYBOARD_BACKLIGHT_DEVICE ".KBQC"
> #define ACPI_KEYBOARD_BACKLIGHT_WRITE ACPI_KEYBOARD_BACKLIGHT_DEVICE ".KBCM"
>
> -#define ACPI_KEYBOARD_BACKLIGHT_MAX 100
> -
> static void keyboard_led_set_brightness_acpi(struct led_classdev *cdev,
> enum led_brightness brightness)
> {
> @@ -107,7 +114,7 @@ static const struct keyboard_led_drvdata keyboard_led_drvdata_acpi = {
> .init = keyboard_led_init_acpi,
> .brightness_set = keyboard_led_set_brightness_acpi,
> .brightness_get = keyboard_led_get_brightness_acpi,
> - .max_brightness = ACPI_KEYBOARD_BACKLIGHT_MAX,
> + .max_brightness = KEYBOARD_BACKLIGHT_MAX,
> };
>
> #else /* CONFIG_CROS_KBD_LED_BACKLIGHT_ACPI */
> @@ -123,34 +130,122 @@ static const struct keyboard_led_drvdata keyboard_led_drvdata_acpi = {
>
> #endif /* CONFIG_CROS_KBD_LED_BACKLIGHT_ACPI */
>
> +#ifdef CONFIG_CROS_KBD_LED_BACKLIGHT_EC_PWM
> +
> +static int
> +keyboard_led_set_brightness_blocking_ec_pwm(struct led_classdev *cdev,
> + enum led_brightness brightness)

nit: since there is only a blocking version of .set_brightness you could omit
'blocking' in the function name.

> +{
> + struct {
> + struct cros_ec_command msg;
> + struct ec_params_pwm_set_keyboard_backlight params;
> + } __packed buf;
> + struct ec_params_pwm_set_keyboard_backlight *params = &buf.params;
> + struct cros_ec_command *msg = &buf.msg;
> + struct keyboard_led_private *private =
> + container_of(cdev, struct keyboard_led_private, cdev);
> +
> + memset(&buf, 0, sizeof(buf));
> +
> + msg->version = 0;

not strictly needed since you do the memset above, I guess it's
fine to keep the assignment if you want to be explicit about the
version.

> + msg->command = EC_CMD_PWM_SET_KEYBOARD_BACKLIGHT;
> + msg->insize = 0;
> + msg->outsize = sizeof(*params);
> +
> + params->percent = brightness;
> +
> + return cros_ec_cmd_xfer_status(private->ec, msg);
> +}
> +
> +static enum led_brightness
> +keyboard_led_get_brightness_ec_pwm(struct led_classdev *cdev)
> +{
> + struct {
> + struct cros_ec_command msg;
> + struct ec_response_pwm_get_keyboard_backlight resp;
> + } __packed buf;
> + struct ec_response_pwm_get_keyboard_backlight *resp = &buf.resp;
> + struct cros_ec_command *msg = &buf.msg;
> + struct keyboard_led_private *private =
> + container_of(cdev, struct keyboard_led_private, cdev);
> + int ret;
> +
> + memset(&buf, 0, sizeof(buf));
> +
> + msg->version = 0;
> + msg->command = EC_CMD_PWM_GET_KEYBOARD_BACKLIGHT;
> + msg->insize = sizeof(*resp);
> + msg->outsize = 0;
> +
> + ret = cros_ec_cmd_xfer_status(private->ec, msg);
> + if (ret < 0)
> + return ret;
> +
> + return resp->percent;
> +}
> +
> +static int keyboard_led_init_ec_pwm(struct platform_device *pdev)
> +{
> + struct keyboard_led_private *private = platform_get_drvdata(pdev);
> +
> + private->ec = dev_get_drvdata(pdev->dev.parent);
> + if (!private->ec) {
> + dev_err(&pdev->dev, "no parent EC device\n");
> + return -EINVAL;
> + }

The only thing this 'init' function does is assigning private->ec. Wouldn't
it be clearer to do this directly in probe() from where callback is called?
It could be with the condition that the device as a DT node.

Is it actually possible that the keyboard backlight device gets instantiated
if there is no EC parent?

> +
> + return 0;
> +}
> +
> +static const struct keyboard_led_drvdata keyboard_led_drvdata_ec_pwm = {
> + .init = keyboard_led_init_ec_pwm,
> + .brightness_set_blocking = keyboard_led_set_brightness_blocking_ec_pwm,
> + .brightness_get = keyboard_led_get_brightness_ec_pwm,
> + .max_brightness = KEYBOARD_BACKLIGHT_MAX,
> +};
> +
> +#else /* CONFIG_CROS_KBD_LED_BACKLIGHT_EC_PWM */
> +
> +static int keyboard_led_init_ec_pwm_null(struct platform_device *pdev)
> +{
> + return -EOPNOTSUPP;
> +}
> +
> +static const struct keyboard_led_drvdata keyboard_led_drvdata_ec_pwm = {
> + .init = keyboard_led_init_ec_pwm_null,

Is this really needed?

keyboard_led_probe() checks if .init is assigned before invoking the callback:

if (drvdata->init) {
error = drvdata->init(pdev);

The whole 'else' branch could be eliminated if .of_match_table of the driver
only is assigned when CONFIG_CROS_KBD_LED_BACKLIGHT_EC_PWM is set. IMO that
would preferable over creating 'stubs'.

> +};
> +
> +#endif /* CONFIG_CROS_KBD_LED_BACKLIGHT_EC_PWM */
> +
> static int keyboard_led_probe(struct platform_device *pdev)
> {
> - struct led_classdev *cdev;
> const struct keyboard_led_drvdata *drvdata;
> + struct keyboard_led_private *private;
> int error;
>
> drvdata = device_get_match_data(&pdev->dev);
> if (!drvdata)
> return -EINVAL;
>
> + private = devm_kzalloc(&pdev->dev, sizeof(*private), GFP_KERNEL);
> + if (!private)
> + return -ENOMEM;
> + platform_set_drvdata(pdev, private);
> +
> if (drvdata->init) {
> error = drvdata->init(pdev);
> if (error)
> return error;
> }
>
> - cdev = devm_kzalloc(&pdev->dev, sizeof(*cdev), GFP_KERNEL);
> - if (!cdev)
> - return -ENOMEM;
> -
> - cdev->name = "chromeos::kbd_backlight";
> - cdev->flags |= LED_CORE_SUSPENDRESUME;
> - cdev->max_brightness = drvdata->max_brightness;
> - cdev->brightness_set = drvdata->brightness_set;
> - cdev->brightness_set_blocking = drvdata->brightness_set_blocking;
> - cdev->brightness_get = drvdata->brightness_get;
> + private->cdev.name = "chromeos::kbd_backlight";
> + private->cdev.flags |= LED_CORE_SUSPENDRESUME;
> + private->cdev.max_brightness = drvdata->max_brightness;
> + private->cdev.brightness_set = drvdata->brightness_set;
> + private->cdev.brightness_set_blocking = drvdata->brightness_set_blocking;
> + private->cdev.brightness_get = drvdata->brightness_get;
>
> - error = devm_led_classdev_register(&pdev->dev, cdev);
> + error = devm_led_classdev_register(&pdev->dev, &private->cdev);
> if (error)
> return error;
>
> @@ -169,6 +264,7 @@ MODULE_DEVICE_TABLE(acpi, keyboard_led_acpi_match);
> static const struct of_device_id keyboard_led_of_match[] = {
> {
> .compatible = "google,cros-kbd-led-backlight",
> + .data = &keyboard_led_drvdata_ec_pwm,
> },
> {}
> };
> --
> 2.35.1.894.gb6a874cedc-goog
>