regmap: rework ->max_register handling

When regmap consists of single register, 'regmap' subsystem is unable to
understand whether ->max_register is set or not, because in both cases it
is equal to zero. It leads to that the logic based on value of
->max_register doesn't work. For example using of REGCACHE_FLAT fails.

This patch introduces an extra parameter to regmap config, indicating
that zero value in ->max_register is authentic.

Signed-off-by: Jan Dakinevich <jan.dakinevich@salutedevices.com>
Link: https://lore.kernel.org/r/20240126200836.1829995-1-jan.dakinevich@salutedevices.com
Signed-off-by: Mark Brown <broonie@kernel.org>

1 files changed, 5 insertions, 0 deletions

diff --git a/include/linux/regmap.h b/include/linux/regmap.h
index c9182a47736e..b743241cfb7c 100644
--- a/include/linux/regmap.h
+++ b/include/linux/regmap.h
@@ -332,6 +332,10 @@ typedef void (*regmap_unlock)(void *);
  * @io_port:	  Support IO port accessors. Makes sense only when MMIO vs. IO port
  *		  access can be distinguished.
  * @max_register: Optional, specifies the maximum valid register address.
+ * @max_register_is_0: Optional, specifies that zero value in @max_register
+ *                     should be taken into account. This is a workaround to
+ *                     apply handling of @max_register for regmap that contains
+ *                     only one register.
  * @wr_table:     Optional, points to a struct regmap_access_table specifying
  *                valid ranges for write access.
  * @rd_table:     As above, for read access.
@@ -422,6 +426,7 @@ struct regmap_config {
 	bool io_port;
 
 	unsigned int max_register;
+	bool max_register_is_0;
 	const struct regmap_access_table *wr_table;
 	const struct regmap_access_table *rd_table;
 	const struct regmap_access_table *volatile_table;