leds: mlxreg: Add support for capability register

Add support for capability register in order to distinct between the
systems with minor LED configuration differences. It reduces the amount
of code describing systems' LED configuration.
For example one system can be equipped with six LED, while the other
with only four. Reading this information from the capability registers
allows to use the same LED structure for such systems and set the
relevant configuration dynamically based on capability register
content.
Signed-off-by: Vadim Pasternak <vadimp@mellanox.com>
Acked-by: Jacek Anaszewski <jacek.anaszewski@gmail.com>
Signed-off-by: Darren Hart (VMware) <dvhart@infradead.org>

drivers/leds/leds-mlxreg.c

@@ -22,6 +22,7 @@
 #define MLXREG_LED_AMBER_SOLID		0x09 /* Solid amber */
 #define MLXREG_LED_BLINK_3HZ		167 /* ~167 msec off/on - HW support */
 #define MLXREG_LED_BLINK_6HZ		83 /* ~83 msec off/on - HW support */
+#define MLXREG_LED_CAPABILITY_CLEAR	GENMASK(31, 8) /* Clear mask */
 
 /**
  * struct mlxreg_led_data - led control data:
@@ -187,6 +188,7 @@ static int mlxreg_led_config(struct mlxreg_led_priv_data *priv)
 	struct mlxreg_led_data *led_data;
 	struct led_classdev *led_cdev;
 	enum led_brightness brightness;
+	u32 regval;
 	int i;
 	int err;
 
@@ -196,6 +198,23 @@ static int mlxreg_led_config(struct mlxreg_led_priv_data *priv)
 		if (!led_data)
 			return -ENOMEM;
 
+		if (data->capability) {
+			err = regmap_read(led_pdata->regmap, data->capability,
+					  &regval);
+			if (err) {
+				dev_err(&priv->pdev->dev, "Failed to query capability register\n");
+				return err;
+			}
+			if (!(regval & data->bit))
+				continue;
+			/*
+			 * Field "bit" can contain one capability bit in 0 byte
+			 * and offset bit in 1-3 bytes. Clear capability bit and
+			 * keep only offset bit.
+			 */
+			data->bit &= MLXREG_LED_CAPABILITY_CLEAR;
+		}
+
 		led_cdev = &led_data->led_cdev;
 		led_data->data_parent = priv;
 		if (strstr(data->label, "red") ||