[PATCH] regmap: add WARN_ONCE when invalid mask is provided to regmap_field_init()

[Matt Ranostay]

In regmap_field_init() when a invalid mask is provided it still
initializes without any warnings of it being incorrect.

An example of this is when the LSB is greater than MSB a mask of zero
is produced.

WARN_ONCE() is not ideal for this but requires less changes to core regmap
code.

Based on: https://lore.kernel.org/all/20220708013125.313892-1-mranostay@ti.com/

Signed-off-by: Matt Ranostay <mranostay at ti.com>
---
 drivers/core/regmap.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/core/regmap.c b/drivers/core/regmap.c
index 5f98f85cfce..3100a58af2c 100644
--- a/drivers/core/regmap.c
+++ b/drivers/core/regmap.c
@@ -20,6 +20,7 @@
 #include <linux/compat.h>
 #include <linux/err.h>
 #include <linux/bitops.h>
+#include <linux/bug.h>
 
 /*
  * Internal representation of a regmap field. Instead of storing the MSB and
@@ -649,6 +650,8 @@ static void regmap_field_init(struct regmap_field *rm_field,
 	rm_field->reg = reg_field.reg;
 	rm_field->shift = reg_field.lsb;
 	rm_field->mask = GENMASK(reg_field.msb, reg_field.lsb);
+
+	WARN_ONCE(rm_field->mask == 0, "invalid empty mask defined\n");
 }
 
 struct regmap_field *devm_regmap_field_alloc(struct udevice *dev,
-- 
2.37.2