hwmon: (pmbus/lm25066) Add regulator support

While these chips aren't strictly advertised as voltage regulators per
se, they (aside from the lm25056) support the PMBus OPERATION command
to enable and disable their outputs and have status bits for reporting
various warnings and faults, and can hence usefully support all the
pmbus_regulator_ops operations.
Signed-off-by: Zev Weiss <zev@bewilderbeest.net>
Link: https://lore.kernel.org/r/20220219000742.20126-1-zev@bewilderbeest.netSigned-off-by: Guenter Roeck <linux@roeck-us.net>

drivers/hwmon/pmbus/Kconfig

@@ -174,6 +174,13 @@ config SENSORS_LM25066
 	  This driver can also be built as a module. If so, the module will
 	  be called lm25066.
 
+config SENSORS_LM25066_REGULATOR
+	bool "Regulator support for LM25066 and compatibles"
+	depends on SENSORS_LM25066 && REGULATOR
+	help
+	  If you say yes here you get regulator support for National
+	  Semiconductor LM25066, LM5064, and LM5066.
+
 config SENSORS_LTC2978
 	tristate "Linear Technologies LTC2978 and compatibles"
 	help

drivers/hwmon/pmbus/lm25066.c

@@ -435,6 +435,12 @@ static int lm25066_write_word_data(struct i2c_client *client, int page, int reg,
 	return ret;
 }
 
+#if IS_ENABLED(CONFIG_SENSORS_LM25066_REGULATOR)
+static const struct regulator_desc lm25066_reg_desc[] = {
+	PMBUS_REGULATOR("vout", 0),
+};
+#endif
+
 static const struct i2c_device_id lm25066_id[] = {
 	{"lm25056", lm25056},
 	{"lm25066", lm25066},
@@ -545,6 +551,14 @@ static int lm25066_probe(struct i2c_client *client)
 	info->m[PSC_CURRENT_IN] = info->m[PSC_CURRENT_IN] * shunt / 1000;
 	info->m[PSC_POWER] = info->m[PSC_POWER] * shunt / 1000;
 
+#if IS_ENABLED(CONFIG_SENSORS_LM25066_REGULATOR)
+	/* LM25056 doesn't support OPERATION */
+	if (data->id != lm25056) {
+		info->num_regulators = ARRAY_SIZE(lm25066_reg_desc);
+		info->reg_desc = lm25066_reg_desc;
+	}
+#endif
+
 	return pmbus_do_probe(client, info);
 }