[PATCH v5 1/3] hwmon: (applesmc) Cache fan positions during register initialization

[Shih-Yuan Lee <fourdollars@debian.org>]

To support the read_string callback for fan labels in the modern HWMON
API, load and cache the fan position names in smcreg.fan_positions
during register initialization.

Pre-pad fallback labels with four spaces to match the "+ 4" pointer
arithmetic offset used by all fan labels in the read_string callback.

Signed-off-by: Shih-Yuan Lee <fourdollars@debian.org>
---
 drivers/hwmon/applesmc.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/drivers/hwmon/applesmc.c b/drivers/hwmon/applesmc.c
index 90a14a7f2c4c..9b2d9ecb20c0 100644
--- a/drivers/hwmon/applesmc.c
+++ b/drivers/hwmon/applesmc.c
@@ -133,6 +133,7 @@ static struct applesmc_registers {
 	bool init_complete;		/* true when fully initialized */
 	struct applesmc_entry *cache;	/* cached key entries */
 	const char **index;		/* temperature key index */
+	char fan_positions[10][17];	/* cached fan position labels */
 } smcreg = {
 	.mutex = __MUTEX_INITIALIZER(smcreg.mutex),
 };
@@ -566,7 +567,7 @@ static int applesmc_init_smcreg_try(void)
 {
 	struct applesmc_registers *s = &smcreg;
 	bool left_light_sensor = false, right_light_sensor = false;
-	unsigned int count;
+	unsigned int count, i;
 	u8 tmp[1];
 	int ret;
 
@@ -597,6 +598,16 @@ static int applesmc_init_smcreg_try(void)
 	if (s->fan_count > 10)
 		s->fan_count = 10;
 
+	for (i = 0; i < s->fan_count; i++) {
+		char newkey[5];
+
+		scnprintf(newkey, sizeof(newkey), FAN_ID_FMT, i);
+		ret = applesmc_read_key(newkey, s->fan_positions[i], 16);
+		s->fan_positions[i][16] = 0;
+		if (ret)
+			scnprintf(s->fan_positions[i], 17, "    Fan %d", i);
+	}
+
 	ret = applesmc_get_lower_bound(&s->temp_begin, "T");
 	if (ret)
 		return ret;
-- 
2.39.5