Re: [PATCH RESEND] leds: lp5860: detect and report fault state

[Lee Jones <lee@kernel.org>]

On Thu, 05 Mar 2026, Steffen Trumtrar wrote:

> The lp5860 can detect shorts and open circuits. If an open (LOD) or
> short (LSD) is detected, the global bit in LP5860_FAULT_STATE is set.
> The channel that caused this can be read from the corresponding Dot_lsdX
> and Dot_lodX register and bit offset.
> 
> The global bits can be cleared by writing 0xf to the LOD/LSD_clear
> register.
> 
> Signed-off-by: Steffen Trumtrar <s.trumtrar@pengutronix.de>
> ---
>  Documentation/ABI/testing/sysfs-class-spi-lp5860 |  50 +++++++++
>  drivers/leds/rgb/leds-lp5860-core.c              | 135 +++++++++++++++++++++++
>  include/linux/platform_data/leds-lp5860.h        |  12 +-
>  3 files changed, 196 insertions(+), 1 deletion(-)

I don't have a general issue with this.

Couple of nits to fix.

Also give the LED community chance to take a better look.

> diff --git a/Documentation/ABI/testing/sysfs-class-spi-lp5860 b/Documentation/ABI/testing/sysfs-class-spi-lp5860
> index 80b22a9d66421..ded9eec855bd9 100644
> --- a/Documentation/ABI/testing/sysfs-class-spi-lp5860
> +++ b/Documentation/ABI/testing/sysfs-class-spi-lp5860
> @@ -21,3 +21,53 @@ Contact:        Steffen Trumtrar <kernel@pengutronix.de>
>  Description:
>  	Contains and sets the global brightness for the R color group.
>  	Can be adjusted in 128 steps from 0% to 100% of the maximum brightness.

What is this applied to?

> +
> +What:           /sys/class/spi_master/spi<bus>/spi<bus>.<dev>/fault_state
> +Date:           January 2026
> +KernelVersion:  6.19

Update.

> +Contact:        Steffen Trumtrar <kernel@pengutronix.de>
> +Description:
> +	Contains and sets the global fault state:
> +
> +	* 3: Open and short detected
> +	* 2: Open detected
> +	* 1: Short detected
> +
> +	Can be cleared by writing the corresponding value back to fault_state.
> +
> +	Example usage::
> +
> +		## Read
> +		# cat /sys/class/spi_master/spi<bus>/spi<bus>.<dev>/fault_state
> +		2
> +
> +		## Write
> +		# echo 2 > /sys/class/spi_master/spi<bus>/spi<bus>.<dev>/fault_state
> +
> +What:           /sys/class/spi_master/spi<bus>/spi<bus>.<dev>/fault_state_open
> +Date:           January 2026
> +KernelVersion:  6.19
> +Contact:        Steffen Trumtrar <kernel@pengutronix.de>
> +Description:
> +	Contains all LEDs and channels where an open condition was detected.
> +	The format is ledname:channel.
> +
> +	Example usage::
> +
> +		## Read
> +		# cat /sys/class/spi_master/spi<bus>/spi<bus>.<dev>/fault_state_open
> +		rgb1:0 rgb2:4
> +
> +What:           /sys/class/spi_master/spi<bus>/spi<bus>.<dev>/fault_state_short
> +Date:           May 2025
> +KernelVersion:  6.15
> +Contact:        Steffen Trumtrar <kernel@pengutronix.de>
> +Description:
> +	Contains all LEDs and channels where a short condition was detected.
> +	The format is ledname:channel.
> +
> +	Example usage::
> +
> +		## Read
> +		# cat /sys/class/spi_master/spi<bus>/spi<bus>.<dev>/fault_state_short
> +		rgb1:0 rgb2:4
> diff --git a/drivers/leds/rgb/leds-lp5860-core.c b/drivers/leds/rgb/leds-lp5860-core.c
> index 79a932edd1d24..ef00577a63a73 100644
> --- a/drivers/leds/rgb/leds-lp5860-core.c
> +++ b/drivers/leds/rgb/leds-lp5860-core.c
> @@ -19,6 +19,138 @@ static struct lp5860_led *mcled_cdev_to_led(struct led_classdev_mc *mc_cdev)
>  	return container_of(mc_cdev, struct lp5860_led, mc_cdev);
>  }
>  
> +static const char *lp5860_find_led(struct lp5860 *lp, unsigned int idx)

lp5860_led_name()

> +{
> +	struct mc_subled *mc_led_info;
> +	struct lp5860_led *led;

You could define these inside the scope.

> +	int i, j;
> +
> +	for (i = lp->leds_count - 1; i >= 0; i--) {

What's the reason for counting downwards?

> +		led = &lp->leds[i];
> +
> +		mc_led_info = led->mc_cdev.subled_info;
> +
> +		for (j = 0; j < led->mc_cdev.num_colors; j++) {

for (int j ... ?

> +			if (mc_led_info[j].channel == idx)

Is there no guarantee that j == channel?

Are there gaps?

> +				return led->mc_cdev.led_cdev.dev->kobj.name;
> +		}
> +	}
> +
> +	return 0;
> +}
> +
> +static ssize_t lp5860_fault_state_lod_lsd(struct lp5860 *led, char *buf,

What does that name even mean?

Can it be improved?

> +					  unsigned int reg, unsigned int length)
> +{
> +	unsigned int value = 0;
> +	unsigned int dot, bit;
> +	unsigned int max_bits;
> +	unsigned int offset = 0;
> +	int len = 0;
> +	bool match = false;

This doesn't need to be initialised.

> +	int ret;
> +
> +	for (dot = 0; dot < length; dot++) {
> +		match = false;

-ENOSQUISH - add a '\n'

> +		ret = regmap_read(led->regmap, reg + dot, &value)
> +		if (ret)
> +			return ret;
> +
> +		max_bits = BITS_PER_BYTE;
> +		/* every 3rd Dot_x register only has 2 bits */

Sentences start with an uppercase char.

> +		if (dot % 3 == 2)
> +			max_bits = 2;
> +
> +		for (bit = 0; bit < max_bits; bit++) {
> +			offset++;

-ENOSQUISH - add a '\n'

> +			if (value & BIT(bit)) {
> +				len += sprintf(buf + len, "%s:%d", lp5860_find_led(led, offset),
> +					       offset - 1);
> +				match = true;
> +				len += sprintf(buf + len, " ");
> +			}
> +		}
> +	}
> +
> +	buf[len++] = '\n';
> +
> +	return len;
> +}
> +
> +static ssize_t lp5860_fault_state_open_show(struct device *dev,
> +					    struct device_attribute *attr,
> +					    char *buf)
> +{
> +	struct lp5860 *led = dev_get_drvdata(dev);
> +	unsigned int value = 0;
> +	int ret;
> +
> +	ret = regmap_read(led->regmap, LP5860_REG_FAULT_STATE, &value);
> +	if (ret)
> +		return ret;
> +
> +	if (!(value & LP5860_FAULT_STATE_LOD))
> +		return 0;
> +
> +	return lp5860_fault_state_lod_lsd(led, buf, LP5860_REG_DOT_LOD_START,
> +					  LP5860_DOT_LOD_LENGTH);
> +}
> +static LP5860_DEV_ATTR_R(fault_state_open);
> +
> +static ssize_t lp5860_fault_state_short_show(struct device *dev,
> +					     struct device_attribute *attr, char *buf)
> +{
> +	struct lp5860 *led = dev_get_drvdata(dev);
> +	unsigned int value = 0;

Can regmap_read() succeed and not initialise value?

> +	int ret;
> +
> +	ret = regmap_read(led->regmap, LP5860_REG_FAULT_STATE, &value);
> +	if (ret)
> +		return ret;
> +
> +	if (!(value & LP5860_FAULT_STATE_LSD))
> +		return 0;
> +
> +	return lp5860_fault_state_lod_lsd(led, buf, LP5860_REG_DOT_LSD_START,
> +					  LP5860_DOT_LSD_LENGTH);
> +}
> +static LP5860_DEV_ATTR_R(fault_state_short);
> +
> +static ssize_t lp5860_fault_state_show(struct device *dev,
> +				  struct device_attribute *attr, char *buf)
> +{
> +	struct lp5860 *led = dev_get_drvdata(dev);
> +	unsigned int value = 0;
> +	int ret;
> +
> +	ret = regmap_read(led->regmap, LP5860_REG_FAULT_STATE, &value);
> +	if (ret)
> +		return ret;

-ENOSQUISH - add a '\n'

> +	return sysfs_emit(buf, "%d\n", (value & 0x3));
> +}
> +
> +static ssize_t lp5860_fault_state_store(struct device *dev,
> +					struct device_attribute *attr,
> +					const char *buf, size_t len)
> +{
> +	struct lp5860 *led = dev_get_drvdata(dev);
> +	unsigned int value = 0;
> +	int ret;
> +
> +	if (kstrtoint(buf, 0, &value))
> +		return -EINVAL;
> +
> +	if (value & LP5860_FAULT_STATE_LOD)
> +		ret = regmap_write(led->regmap, LP5860_REG_LOD_CLEAR, 0xf);
> +	if (value & LP5860_FAULT_STATE_LSD)
> +		ret = regmap_write(led->regmap, LP5860_REG_LSD_CLEAR, 0xf);
> +
> +	if (ret < 0)
> +		return ret;

-ENOSQUISH - add a '\n'

> +	return len;
> +}
> +static LP5860_DEV_ATTR_RW(fault_state);
> +
>  LP5860_SHOW_MODE(r_global_brightness_set, LP5860_REG_R_CURRENT_SET, LP5860_CC_GROUP_MASK, 0)
>  LP5860_STORE_MODE(r_global_brightness_set, LP5860_REG_R_CURRENT_SET, LP5860_CC_GROUP_MASK, 0)
>  DEVICE_ATTR_RW(r_global_brightness_set);
> @@ -35,6 +167,9 @@ static struct attribute *lp5860_led_attrs[] = {
>  	&dev_attr_r_global_brightness_set.attr,
>  	&dev_attr_g_global_brightness_set.attr,
>  	&dev_attr_b_global_brightness_set.attr,
> +	&dev_attr_fault_state_open.attr,
> +	&dev_attr_fault_state_short.attr,
> +	&dev_attr_fault_state.attr,
>  	NULL,
>  };
>  
> diff --git a/include/linux/platform_data/leds-lp5860.h b/include/linux/platform_data/leds-lp5860.h
> index 94d184702b11a..d032a0e6d2617 100644
> --- a/include/linux/platform_data/leds-lp5860.h
> +++ b/include/linux/platform_data/leds-lp5860.h
> @@ -189,6 +189,9 @@
>  #define LP5860_DOT_CS_OFF		0x00
>  
>  /* Dot lod value */
> +#define LP5860_FAULT_STATE_LOD		BIT(1)
> +#define LP5860_FAULT_STATE_LSD		BIT(0)

I don't see the point of defines if the nomenclature isn't self explanatory.

>  #define LP5860_DOT_LOD0_OFFSET		0
>  #define LP5860_DOT_LOD1_OFFSET		1
>  #define LP5860_DOT_LOD2_OFFSET		2
> @@ -201,7 +204,9 @@
>  #define LP5860_DOT_LOD_ON		0x01
>  #define LP5860_DOT_LOD_OFF		0x00
>  
> -/* dot lsd value */
> +/* Dot lsd value */
> +#define LP5860_DOT_LOD_LENGTH		0x20
> +
>  #define LP5860_DOT_LSD0_OFFSET		0
>  #define LP5860_DOT_LSD1_OFFSET		1
>  #define LP5860_DOT_LSD2_OFFSET		2
> @@ -215,6 +220,8 @@
>  #define LP5860_DOT_LSD_OFF		0x00
>  
>  /* Register lod state */
> +#define LP5860_DOT_LSD_LENGTH		0x20
> +
>  #define LP5860_GLOBAL_LOD_OFFSET	1
>  #define LP5860_GLOBAL_LOD_STATE		BIT(1)
>  #define LP5860_GLOBAL_LSD_OFFSET	0
> @@ -248,6 +255,9 @@
>   */
>  #define LP5860_MAX_LED_CHANNELS		4
>  
> +#define LP5860_DEV_ATTR_R(name)	\
> +	DEVICE_ATTR(name, 0444, lp5860_##name##_show, NULL)
> +
>  #define LP5860_DEV_ATTR_RW(name)	\
>  	DEVICE_ATTR(name, 0644, lp5860_##name##_show, lp5860_##name##_store)
>  
> 
> ---
> base-commit: d60f615f21e161506b3ac9bee8add471f0e27a8c
> change-id: 20260129-v6-19-topic-ti-lp5860-fault-c8bd1f59fc3f
> 
> Best regards,
> -- 
> Steffen Trumtrar <s.trumtrar@pengutronix.de>
> 
> 

-- 
Lee Jones [李琼斯]