[PATCH v4] light: tsl2591: simplify tsl2591_persist functions via lookup table

[matheus.feitosa em usp.br]

From: Matheus Silveira <matheus.feitosa em usp.br>

Replace switch statements with an indexed lookup table for
persist cycle conversions.

These functions have redundant switch-cases. This reduces
code duplication and makes future updates to
TSL2591_PRST_ALS_INT_CYCLE_* values easier to maintain by
keeping the mapping in one place.

Signed-off-by: Matheus Silveira <matheus.feitosa em usp.br>
Co-developed-by: Lucas Rabaquim <lucas.rabaquim em usp.br>
Signed-off-by: Lucas Rabaquim <lucas.rabaquim em usp.br>
---
Changes in V3:
 - Remove struct persist_entry and replace the struct
   list with an array of u8 values
 - Remove the loop from tsl2591_persist_cycle_to_lit()
   as suggested by Andy Shevchenko
 - Align tsl2591_persist_lit_to_cycle() with
   tsl2591_als_time_to_fval()
 - Keep the loop in tsl2591_persist_lit_to_cycle()
   as suggested during discussion by David Lechner

Changes in V4:
 - Fixed typo in Lucas's name
 - Changed lit_to_cycle into an in-loop declaration.
 - Changed loop initialization to start in 1 since
   0 is not used in the conversion table.
   as suggested by Marcelo Schmitt
---
 drivers/iio/light/tsl2591.c | 95 +++++++++++--------------------------
 1 file changed, 29 insertions(+), 66 deletions(-)

diff --git a/drivers/iio/light/tsl2591.c b/drivers/iio/light/tsl2591.c
index 08476f193a44..2b91ecb86ade 100644
--- a/drivers/iio/light/tsl2591.c
+++ b/drivers/iio/light/tsl2591.c
@@ -192,6 +192,24 @@ static const int tsl2591_calibscale_available[] = {
 	1, 25, 428, 9876,
 };
 
+static const u8 tsl2591_persist_table[] = {
+	[TSL2591_PRST_ALS_INT_CYCLE_ANY] = 1,
+	[TSL2591_PRST_ALS_INT_CYCLE_2]   = 2,
+	[TSL2591_PRST_ALS_INT_CYCLE_3]   = 3,
+	[TSL2591_PRST_ALS_INT_CYCLE_5]   = 5,
+	[TSL2591_PRST_ALS_INT_CYCLE_10]  = 10,
+	[TSL2591_PRST_ALS_INT_CYCLE_15]  = 15,
+	[TSL2591_PRST_ALS_INT_CYCLE_20]  = 20,
+	[TSL2591_PRST_ALS_INT_CYCLE_25]  = 25,
+	[TSL2591_PRST_ALS_INT_CYCLE_30]  = 30,
+	[TSL2591_PRST_ALS_INT_CYCLE_35]  = 35,
+	[TSL2591_PRST_ALS_INT_CYCLE_40]  = 40,
+	[TSL2591_PRST_ALS_INT_CYCLE_45]  = 45,
+	[TSL2591_PRST_ALS_INT_CYCLE_50]  = 50,
+	[TSL2591_PRST_ALS_INT_CYCLE_55]  = 55,
+	[TSL2591_PRST_ALS_INT_CYCLE_60]  = 60,
+};
+
 static int tsl2591_set_als_lower_threshold(struct tsl2591_chip *chip,
 					   u16 als_lower_threshold);
 static int tsl2591_set_als_upper_threshold(struct tsl2591_chip *chip,
@@ -231,78 +249,23 @@ static int tsl2591_multiplier_to_gain(const u32 multiplier)
 
 static int tsl2591_persist_cycle_to_lit(const u8 als_persist)
 {
-	switch (als_persist) {
-	case TSL2591_PRST_ALS_INT_CYCLE_ANY:
-		return 1;
-	case TSL2591_PRST_ALS_INT_CYCLE_2:
-		return 2;
-	case TSL2591_PRST_ALS_INT_CYCLE_3:
-		return 3;
-	case TSL2591_PRST_ALS_INT_CYCLE_5:
-		return 5;
-	case TSL2591_PRST_ALS_INT_CYCLE_10:
-		return 10;
-	case TSL2591_PRST_ALS_INT_CYCLE_15:
-		return 15;
-	case TSL2591_PRST_ALS_INT_CYCLE_20:
-		return 20;
-	case TSL2591_PRST_ALS_INT_CYCLE_25:
-		return 25;
-	case TSL2591_PRST_ALS_INT_CYCLE_30:
-		return 30;
-	case TSL2591_PRST_ALS_INT_CYCLE_35:
-		return 35;
-	case TSL2591_PRST_ALS_INT_CYCLE_40:
-		return 40;
-	case TSL2591_PRST_ALS_INT_CYCLE_45:
-		return 45;
-	case TSL2591_PRST_ALS_INT_CYCLE_50:
-		return 50;
-	case TSL2591_PRST_ALS_INT_CYCLE_55:
-		return 55;
-	case TSL2591_PRST_ALS_INT_CYCLE_60:
-		return 60;
-	default:
+	if (als_persist >= ARRAY_SIZE(tsl2591_persist_table) ||
+	    !tsl2591_persist_table[als_persist])
 		return -EINVAL;
-	}
+
+	return tsl2591_persist_table[als_persist];
 }
 
 static int tsl2591_persist_lit_to_cycle(const u8 als_persist)
 {
-	switch (als_persist) {
-	case 1:
-		return TSL2591_PRST_ALS_INT_CYCLE_ANY;
-	case 2:
-		return TSL2591_PRST_ALS_INT_CYCLE_2;
-	case 3:
-		return TSL2591_PRST_ALS_INT_CYCLE_3;
-	case 5:
-		return TSL2591_PRST_ALS_INT_CYCLE_5;
-	case 10:
-		return TSL2591_PRST_ALS_INT_CYCLE_10;
-	case 15:
-		return TSL2591_PRST_ALS_INT_CYCLE_15;
-	case 20:
-		return TSL2591_PRST_ALS_INT_CYCLE_20;
-	case 25:
-		return TSL2591_PRST_ALS_INT_CYCLE_25;
-	case 30:
-		return TSL2591_PRST_ALS_INT_CYCLE_30;
-	case 35:
-		return TSL2591_PRST_ALS_INT_CYCLE_35;
-	case 40:
-		return TSL2591_PRST_ALS_INT_CYCLE_40;
-	case 45:
-		return TSL2591_PRST_ALS_INT_CYCLE_45;
-	case 50:
-		return TSL2591_PRST_ALS_INT_CYCLE_50;
-	case 55:
-		return TSL2591_PRST_ALS_INT_CYCLE_55;
-	case 60:
-		return TSL2591_PRST_ALS_INT_CYCLE_60;
-	default:
-		return -EINVAL;
+	for (unsigned int i = TSL2591_PRST_ALS_INT_CYCLE_ANY;
+		i < ARRAY_SIZE(tsl2591_persist_table);
+		i++) {
+		if (als_persist == tsl2591_persist_table[i])
+			return i;
 	}
+
+	return -EINVAL;
 }
 
 static int tsl2591_compatible_int_time(struct tsl2591_chip *chip,
-- 
2.43.0