Re: [PATCH v2] hwmon (pmbus): cffps: Add led class device for power supply fault led

[Eddie James <eajames@linux.vnet.ibm.com>]

On 01/10/2018 12:16 PM, Guenter Roeck wrote:
> On Wed, Jan 10, 2018 at 11:29:43AM -0600, Eddie James wrote:
>> This power supply device doesn't correctly manage it's own fault led.
>> Add an led class device and register it so that userspace can manage
>> power supply fault led as necessary.
>>
>> Signed-off-by: Eddie James <eajames@linux.vnet.ibm.com>
>> ---
>>
>>   Changes since v1:
>>   - move led registration into a separate function.
>>   - improve comments.
>>
>>   drivers/hwmon/pmbus/ibm-cffps.c | 99 +++++++++++++++++++++++++++++++++++++----
>>   1 file changed, 91 insertions(+), 8 deletions(-)
>>
>> diff --git a/drivers/hwmon/pmbus/ibm-cffps.c b/drivers/hwmon/pmbus/ibm-cffps.c
>> index 2d6f4f4..cd9f685 100644
>> --- a/drivers/hwmon/pmbus/ibm-cffps.c
>> +++ b/drivers/hwmon/pmbus/ibm-cffps.c
>> @@ -13,6 +13,7 @@
>>   #include <linux/fs.h>
>>   #include <linux/i2c.h>
>>   #include <linux/jiffies.h>
>> +#include <linux/leds.h>
>>   #include <linux/module.h>
>>   #include <linux/mutex.h>
>>   #include <linux/pmbus.h>
>> @@ -25,6 +26,7 @@
>>   #define CFFPS_CCIN_CMD				0xBD
>>   #define CFFPS_FW_CMD_START			0xFA
>>   #define CFFPS_FW_NUM_BYTES			4
>> +#define CFFPS_SYS_CONFIG_CMD			0xDA
>>   
>>   #define CFFPS_INPUT_HISTORY_CMD			0xD6
>>   #define CFFPS_INPUT_HISTORY_SIZE		100
>> @@ -39,6 +41,11 @@
>>   #define CFFPS_MFR_VAUX_FAULT			BIT(6)
>>   #define CFFPS_MFR_CURRENT_SHARE_WARNING		BIT(7)
>>   
>> +#define CFFPS_LED_BLINK				BIT(0)
>> +#define CFFPS_LED_ON				BIT(1)
>> +#define CFFPS_LED_OFF				BIT(2)
>> +#define CFFPS_BLINK_RATE_MS			250
>> +
>>   enum {
>>   	CFFPS_DEBUGFS_INPUT_HISTORY = 0,
>>   	CFFPS_DEBUGFS_FRU,
>> @@ -63,6 +70,9 @@ struct ibm_cffps {
>>   	struct ibm_cffps_input_history input_history;
>>   
>>   	int debugfs_entries[CFFPS_DEBUGFS_NUM_ENTRIES];
>> +
>> +	u8 led_state;
>> +	struct led_classdev led;
>>   };
>>   
>>   #define to_psu(x, y) container_of((x), struct ibm_cffps, debugfs_entries[(y)])
>> @@ -258,6 +268,69 @@ static int ibm_cffps_read_word_data(struct i2c_client *client, int page,
>>   	return rc;
>>   }
>>   
>> +static void ibm_cffps_led_brightness_set(struct led_classdev *led_cdev,
>> +					 enum led_brightness brightness)
>> +{
>> +	int rc;
>> +	struct ibm_cffps *psu = container_of(led_cdev, struct ibm_cffps, led);
>> +
>> +	if (brightness == LED_OFF) {
>> +		psu->led_state = CFFPS_LED_OFF;
>> +	} else {
>> +		brightness = LED_FULL;
>> +		if (psu->led_state != CFFPS_LED_BLINK)
>> +			psu->led_state = CFFPS_LED_ON;
>> +	}
>> +
>> +	rc = i2c_smbus_write_byte_data(psu->client, CFFPS_SYS_CONFIG_CMD,
>> +				       psu->led_state);
>> +	if (rc < 0)
>> +		return;
>> +
>> +	led_cdev->brightness = brightness;
>> +}
>> +
>> +static int ibm_cffps_led_blink_set(struct led_classdev *led_cdev,
>> +				   unsigned long *delay_on,
>> +				   unsigned long *delay_off)
>> +{
>> +	int rc;
>> +	struct ibm_cffps *psu = container_of(led_cdev, struct ibm_cffps, led);
>> +
>> +	psu->led_state = CFFPS_LED_BLINK;
>> +
>> +	if (led_cdev->brightness == LED_OFF)
>> +		return 0;
>> +
>> +	rc = i2c_smbus_write_byte_data(psu->client, CFFPS_SYS_CONFIG_CMD,
>> +				       CFFPS_LED_BLINK);
>> +	if (rc < 0)
>> +		return rc;
>> +
>> +	*delay_on = CFFPS_BLINK_RATE_MS;
>> +	*delay_off = CFFPS_BLINK_RATE_MS;
>> +
>> +	return 0;
>> +}
>> +
>> +static void ibm_cffps_create_led_class(size_t name_size, struct ibm_cffps *psu)
>> +{
>> +	int rc;
>> +	struct i2c_client *client = psu->client;
>> +	struct device *dev = &client->dev;
>> +	char *led_name = (void *)(&psu[1]);
>> +
> I really dislike this hack. Why not allocate a sufficient
> fixed length, say, 32 bytes, and just use it ? If you want
> to be really wasteful, use 48 or 64 bytes; that is still better
> than this code.

That's fair, I found this trick in some sony hid driver, but fixed 
length is much cleaner.

>
>> +	snprintf(led_name, name_size, "%s-%x", client->name, client->addr);
> %02x, maybe ? Your call, though.
>
> Thanks,
> Guenter
>
>> +	psu->led.name = led_name;
>> +	psu->led.max_brightness = LED_FULL;
>> +	psu->led.brightness_set = ibm_cffps_led_brightness_set;
>> +	psu->led.blink_set = ibm_cffps_led_blink_set;
>> +
>> +	rc = devm_led_classdev_register(dev, &psu->led);
>> +	if (rc)
>> +		dev_warn(dev, "failed to register led class: %d\n", rc);
>> +}
>> +
>>   static struct pmbus_driver_info ibm_cffps_info = {
>>   	.pages = 1,
>>   	.func[0] = PMBUS_HAVE_VIN | PMBUS_HAVE_VOUT | PMBUS_HAVE_IOUT |
>> @@ -277,6 +350,7 @@ static int ibm_cffps_probe(struct i2c_client *client,
>>   			   const struct i2c_device_id *id)
>>   {
>>   	int i, rc;
>> +	size_t name_size;
>>   	struct dentry *debugfs;
>>   	struct dentry *ibm_cffps_dir;
>>   	struct ibm_cffps *psu;
>> @@ -286,6 +360,23 @@ static int ibm_cffps_probe(struct i2c_client *client,
>>   	if (rc)
>>   		return rc;
>>   
>> +	/* client name, '-', 8 chars for addr, and null terminator */
>> +	name_size = strlen(client->name) + 10;
>> +
>> +	/*
>> +	 * Don't fail the probe if there isn't enough memory for leds and
>> +	 * debugfs.
>> +	 */
>> +	psu = devm_kzalloc(&client->dev, sizeof(*psu) + name_size, GFP_KERNEL);
>> +	if (!psu)
>> +		return 0;
>> +
>> +	psu->client = client;
>> +	mutex_init(&psu->input_history.update_lock);
>> +	psu->input_history.last_update = jiffies - HZ;
>> +
>> +	ibm_cffps_create_led_class(name_size, psu);
>> +
>>   	/* Don't fail the probe if we can't create debugfs */
>>   	debugfs = pmbus_get_debugfs_dir(client);
>>   	if (!debugfs)
>> @@ -295,14 +386,6 @@ static int ibm_cffps_probe(struct i2c_client *client,
>>   	if (!ibm_cffps_dir)
>>   		return 0;
>>   
>> -	psu = devm_kzalloc(&client->dev, sizeof(*psu), GFP_KERNEL);
>> -	if (!psu)
>> -		return 0;
>> -
>> -	psu->client = client;
>> -	mutex_init(&psu->input_history.update_lock);
>> -	psu->input_history.last_update = jiffies - HZ;
>> -
>>   	for (i = 0; i < CFFPS_DEBUGFS_NUM_ENTRIES; ++i)
>>   		psu->debugfs_entries[i] = i;
>>   
>> -- 
>> 1.8.3.1
>>