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

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

[Gwendal Grignou]

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.

Signed-off-by: Gwendal Grignou <gwendal@google.com>
---
 drivers/platform/chrome/cros_ec_lightbar.c    | 46 +++++++++++++++++++
 .../linux/platform_data/cros_ec_commands.h    | 11 +++++
 2 files changed, 57 insertions(+)

diff --git a/drivers/platform/chrome/cros_ec_lightbar.c b/drivers/platform/chrome/cros_ec_lightbar.c
index 87634f6921b7..85f30c8dfba3 100644
--- a/drivers/platform/chrome/cros_ec_lightbar.c
+++ b/drivers/platform/chrome/cros_ec_lightbar.c
@@ -173,6 +173,50 @@ static ssize_t version_show(struct device *dev,
 	return sysfs_emit(buf, "%d %d\n", version, flags);
 }
 
+static ssize_t num_segments_show(struct device *dev,
+				 struct device_attribute *attr, char *buf)
+{
+	uint32_t num = 0;
+	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;
+
+	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);
+	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);
+}
+
 static ssize_t brightness_store(struct device *dev,
 				struct device_attribute *attr,
 				const char *buf, size_t count)
@@ -505,6 +549,7 @@ static ssize_t userspace_control_store(struct device *dev,
 /* Module initialization */
 
 static DEVICE_ATTR_RW(interval_msec);
+static DEVICE_ATTR_RO(num_segments);
 static DEVICE_ATTR_RO(version);
 static DEVICE_ATTR_WO(brightness);
 static DEVICE_ATTR_WO(led_rgb);
@@ -514,6 +559,7 @@ static DEVICE_ATTR_RW(userspace_control);
 
 static struct attribute *__lb_cmds_attrs[] = {
 	&dev_attr_interval_msec.attr,
+	&dev_attr_num_segments.attr,
 	&dev_attr_version.attr,
 	&dev_attr_brightness.attr,
 	&dev_attr_led_rgb.attr,
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
 };
 
-- 
2.52.0.457.g6b5491de43-goog

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

[Tzung-Bi Shih]

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?

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

[Gwendal Grignou]

On Sun, Jan 25, 2026 at 11:13 PM Tzung-Bi Shih <tzungbi@kernel.org> wrote:
>
> 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.
Done (in v2).
>
> > +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'
I kept `uint...` to be consistent with the rest of the code.
>
> > +     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.
Done
>
> > +
> > +     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;
Done.
>
>
> > 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?
For reference, crrev.com/c/7515877. Will post v2 once the change lands.