firmware: exynos-acpm: Drop fake 'const' on handle pointer

All the functions operating on the 'handle' pointer are claiming it is a
pointer to const thus they should not modify the handle.  In fact that's
a false statement, because first thing these functions do is drop the
cast to const with container_of:

  struct acpm_info *acpm = handle_to_acpm_info(handle);

And with such cast the handle is easily writable with simple:

  acpm->handle.ops.pmic_ops.read_reg = NULL;

The code is not correct logically, either, because functions like
acpm_get_by_node() and acpm_handle_put() are meant to modify the handle
reference counting, thus they must modify the handle.  Modification here
happens anyway, even if the reference counting is stored in the
container which the handle is part of.

The code does not have actual visible bug, but incorrect 'const'
annotations could lead to incorrect compiler decisions.

Fixes: a88927b534ba ("firmware: add Exynos ACPM protocol driver")
Cc: stable@vger.kernel.org
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>
Link: https://patch.msgid.link/20260224104203.42950-2-krzysztof.kozlowski@oss.qualcomm.com
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>

1 files changed, 17 insertions, 23 deletions

diff --git a/include/linux/firmware/samsung/exynos-acpm-protocol.h b/include/linux/firmware/samsung/exynos-acpm-protocol.h
index 2091da965a5a..13f17dc4443b 100644
--- a/include/linux/firmware/samsung/exynos-acpm-protocol.h
+++ b/include/linux/firmware/samsung/exynos-acpm-protocol.h
@@ -14,30 +14,24 @@ struct acpm_handle;
 struct device_node;
 
 struct acpm_dvfs_ops {
-	int (*set_rate)(const struct acpm_handle *handle,
-			unsigned int acpm_chan_id, unsigned int clk_id,
-			unsigned long rate);
-	unsigned long (*get_rate)(const struct acpm_handle *handle,
+	int (*set_rate)(struct acpm_handle *handle, unsigned int acpm_chan_id,
+			unsigned int clk_id, unsigned long rate);
+	unsigned long (*get_rate)(struct acpm_handle *handle,
 				  unsigned int acpm_chan_id,
 				  unsigned int clk_id);
 };
 
 struct acpm_pmic_ops {
-	int (*read_reg)(const struct acpm_handle *handle,
-			unsigned int acpm_chan_id, u8 type, u8 reg, u8 chan,
-			u8 *buf);
-	int (*bulk_read)(const struct acpm_handle *handle,
-			 unsigned int acpm_chan_id, u8 type, u8 reg, u8 chan,
-			 u8 count, u8 *buf);
-	int (*write_reg)(const struct acpm_handle *handle,
-			 unsigned int acpm_chan_id, u8 type, u8 reg, u8 chan,
-			 u8 value);
-	int (*bulk_write)(const struct acpm_handle *handle,
-			  unsigned int acpm_chan_id, u8 type, u8 reg, u8 chan,
-			  u8 count, const u8 *buf);
-	int (*update_reg)(const struct acpm_handle *handle,
-			  unsigned int acpm_chan_id, u8 type, u8 reg, u8 chan,
-			  u8 value, u8 mask);
+	int (*read_reg)(struct acpm_handle *handle, unsigned int acpm_chan_id,
+			u8 type, u8 reg, u8 chan, u8 *buf);
+	int (*bulk_read)(struct acpm_handle *handle, unsigned int acpm_chan_id,
+			 u8 type, u8 reg, u8 chan, u8 count, u8 *buf);
+	int (*write_reg)(struct acpm_handle *handle, unsigned int acpm_chan_id,
+			 u8 type, u8 reg, u8 chan, u8 value);
+	int (*bulk_write)(struct acpm_handle *handle, unsigned int acpm_chan_id,
+			  u8 type, u8 reg, u8 chan, u8 count, const u8 *buf);
+	int (*update_reg)(struct acpm_handle *handle, unsigned int acpm_chan_id,
+			  u8 type, u8 reg, u8 chan, u8 value, u8 mask);
 };
 
 struct acpm_ops {
@@ -56,12 +50,12 @@ struct acpm_handle {
 struct device;
 
 #if IS_ENABLED(CONFIG_EXYNOS_ACPM_PROTOCOL)
-const struct acpm_handle *devm_acpm_get_by_node(struct device *dev,
-						struct device_node *np);
+struct acpm_handle *devm_acpm_get_by_node(struct device *dev,
+					  struct device_node *np);
 #else
 
-static inline const struct acpm_handle *devm_acpm_get_by_node(struct device *dev,
-							      struct device_node *np)
+static inline struct acpm_handle *devm_acpm_get_by_node(struct device *dev,
+							struct device_node *np)
 {
 	return NULL;
 }