Re: [PATCH 1/2] chrome: lightbar: Report number of segments

[Tzung-Bi Shih <tzungbi@kernel.org>]

On Sat, Jan 24, 2026 at 12:58:55AM -0800, Gwendal Grignou wrote:
> Add attribue `num_segments` to return the number of exposed LED segments
> in the lightbar. It can be smaller than the number of physical leds in
> the lightbar.
> 
> Test: Check the attribute is present and returns a value when read.

Please use "platform/chrome" prefix for the commit title.

> +static ssize_t num_segments_show(struct device *dev,
> +				 struct device_attribute *attr, char *buf)
> +{
> +	uint32_t num = 0;

`./scripts/checkpatch.pl --strict`:
CHECK: Prefer kernel type 'u32' over 'uint32_t'

> +	struct cros_ec_dev *ec = to_cros_ec_dev(dev);
> +	int ret;
> +
> +	ret = lb_throttle();
> +	if (ret)
> +		return ret;
> +
> +	struct ec_params_lightbar *param;
> +	struct ec_response_lightbar *resp;
> +	struct cros_ec_command *msg;

For clarity, I prefer to move the 3 declarations before calling lb_throttle()
in the case.

> +
> +	msg = alloc_lightbar_cmd_msg(ec);
> +	if (!msg)
> +		return -ENOMEM;
> +
> +	param = (struct ec_params_lightbar *)msg->data;
> +	param->cmd = LIGHTBAR_CMD_GET_PARAMS_V3;
> +	msg->outsize = sizeof(param->cmd);
> +	msg->result = sizeof(resp->get_params_v3);
             ^^^^^^ insize

> +	ret = cros_ec_cmd_xfer_status(ec->ec_dev, msg);
> +	if (ret < 0 && ret != -EINVAL)
> +		goto exit;
> +
> +	if (msg->result == EC_RES_SUCCESS) {
> +		resp = (struct ec_response_lightbar *)msg->data;
> +		num = resp->get_params_v3.reported_led_num;
> +	}
> +
> +	/*
> +	 * Anything else (ie, EC_RES_INVALID_COMMAND) - no direct control over
> +	 * LEDs, return that no leds are supported.
> +	 */
> +	ret = 0;
> +exit:
> +	kfree(msg);
> +	if (ret)
> +		return ret;
> +	return sysfs_emit(buf, "%d\n", num);
                                 ^ `num` is an u32.
> +}

How about:

      ret = sysfs_emit(buf, "%u\n", num);
  exit:
      kfree(msg);
      return ret;


> diff --git a/include/linux/platform_data/cros_ec_commands.h b/include/linux/platform_data/cros_ec_commands.h
> index 69294f79cc88..9cbf024f56c3 100644
> --- a/include/linux/platform_data/cros_ec_commands.h
> +++ b/include/linux/platform_data/cros_ec_commands.h
> @@ -2005,6 +2005,14 @@ struct lightbar_params_v2_colors {
>  	struct rgb_s color[8];			/* 0-3 are Google colors */
>  } __ec_todo_packed;
>  
> +struct lightbar_params_v3 {
> +	/*
> +	 *  Number of LEDs reported by the EC.
> +	 *  May be less than the actual number of LEDs in the lightbar.
> +	 */
> +	uint8_t reported_led_num;
> +} __ec_todo_packed;
> +
>  /* Lightbar program. */
>  #define EC_LB_PROG_LEN 192
>  struct lightbar_program {
> @@ -2086,6 +2094,8 @@ struct ec_response_lightbar {
>  		struct lightbar_params_v2_thresholds get_params_v2_thlds;
>  		struct lightbar_params_v2_colors get_params_v2_colors;
>  
> +		struct lightbar_params_v3 get_params_v3;
> +
>  		struct __ec_todo_unpacked {
>  			uint32_t num;
>  			uint32_t flags;
> @@ -2143,6 +2153,7 @@ enum lightbar_command {
>  	LIGHTBAR_CMD_SET_PARAMS_V2_THRESHOLDS = 31,
>  	LIGHTBAR_CMD_GET_PARAMS_V2_COLORS = 32,
>  	LIGHTBAR_CMD_SET_PARAMS_V2_COLORS = 33,
> +	LIGHTBAR_CMD_GET_PARAMS_V3 = 34,
>  	LIGHTBAR_NUM_CMDS
>  };

Haven't seen the change in
https://chromium.googlesource.com/chromiumos/platform/ec/+/refs/heads/main/include/ec_commands.h,
do we need to wait until the change landed in EC firmware?