[PATCH v4 05/11] firmware: samsung: acpm: Make acpm_ops const and access via pointer

[Tudor Ambarus]

Replace the embedded `struct acpm_ops` inside `struct acpm_handle` with
a pointer to a `const struct acpm_ops`.

Previously, the operations structure was embedded directly within the
handle and populated dynamically at runtime via `acpm_setup_ops()`.
This resulted in mutable function pointers and unnecessary per-instance
memory overhead.

By defining `exynos_acpm_driver_ops` statically as a `const` structure,
the function pointers are now safely housed in the read-only `.rodata`
section. This improves security by preventing function pointer
overwrites, saves memory, and slightly reduces initialization overhead
in `acpm_probe()`.

Consequently, update all consumer drivers (clk, mfd) to access the
operations via the new pointer indirection (`->ops->`). Finally, fix
the previously empty kernel-doc description for the ops member to
reflect its new pointer nature.

Signed-off-by: Tudor Ambarus <tudor.ambarus at linaro.org>
---
 drivers/clk/samsung/clk-acpm.c                     |  8 ++---
 drivers/firmware/samsung/exynos-acpm.c             | 36 ++++++++++------------
 drivers/mfd/sec-acpm.c                             |  6 ++--
 .../linux/firmware/samsung/exynos-acpm-protocol.h  |  4 +--
 4 files changed, 25 insertions(+), 29 deletions(-)

diff --git a/drivers/clk/samsung/clk-acpm.c b/drivers/clk/samsung/clk-acpm.c
index 93667777094c..953ca8d5720a 100644
--- a/drivers/clk/samsung/clk-acpm.c
+++ b/drivers/clk/samsung/clk-acpm.c
@@ -68,8 +68,8 @@ static unsigned long acpm_clk_recalc_rate(struct clk_hw *hw,
 {
 	struct acpm_clk *clk = to_acpm_clk(hw);
 
-	return clk->handle->ops.dvfs.get_rate(clk->handle, clk->mbox_chan_id,
-					      clk->id);
+	return clk->handle->ops->dvfs.get_rate(clk->handle, clk->mbox_chan_id,
+					       clk->id);
 }
 
 static int acpm_clk_determine_rate(struct clk_hw *hw,
@@ -89,8 +89,8 @@ static int acpm_clk_set_rate(struct clk_hw *hw, unsigned long rate,
 {
 	struct acpm_clk *clk = to_acpm_clk(hw);
 
-	return clk->handle->ops.dvfs.set_rate(clk->handle, clk->mbox_chan_id,
-					      clk->id, rate);
+	return clk->handle->ops->dvfs.set_rate(clk->handle, clk->mbox_chan_id,
+					       clk->id, rate);
 }
 
 static const struct clk_ops acpm_clk_ops = {
diff --git a/drivers/firmware/samsung/exynos-acpm.c b/drivers/firmware/samsung/exynos-acpm.c
index a2cd54ee4589..38f40fb67ea7 100644
--- a/drivers/firmware/samsung/exynos-acpm.c
+++ b/drivers/firmware/samsung/exynos-acpm.c
@@ -621,30 +621,26 @@ static int acpm_channels_init(struct acpm_info *acpm)
 	return 0;
 }
 
-/**
- * acpm_setup_ops() - setup the operations structures.
- * @acpm:	pointer to the driver data.
- */
-static void acpm_setup_ops(struct acpm_info *acpm)
-{
-	struct acpm_dvfs_ops *dvfs_ops = &acpm->handle.ops.dvfs;
-	struct acpm_pmic_ops *pmic_ops = &acpm->handle.ops.pmic;
-
-	dvfs_ops->set_rate = acpm_dvfs_set_rate;
-	dvfs_ops->get_rate = acpm_dvfs_get_rate;
-
-	pmic_ops->read_reg = acpm_pmic_read_reg;
-	pmic_ops->bulk_read = acpm_pmic_bulk_read;
-	pmic_ops->write_reg = acpm_pmic_write_reg;
-	pmic_ops->bulk_write = acpm_pmic_bulk_write;
-	pmic_ops->update_reg = acpm_pmic_update_reg;
-}
-
 static void acpm_clk_pdev_unregister(void *data)
 {
 	platform_device_unregister(data);
 }
 
+static const struct acpm_ops exynos_acpm_driver_ops = {
+	.dvfs = {
+		.set_rate = acpm_dvfs_set_rate,
+		.get_rate = acpm_dvfs_get_rate,
+	},
+
+	.pmic = {
+		.read_reg = acpm_pmic_read_reg,
+		.bulk_read = acpm_pmic_bulk_read,
+		.write_reg = acpm_pmic_write_reg,
+		.bulk_write = acpm_pmic_bulk_write,
+		.update_reg = acpm_pmic_update_reg,
+	},
+};
+
 static int acpm_probe(struct platform_device *pdev)
 {
 	const struct acpm_match_data *match_data;
@@ -689,7 +685,7 @@ static int acpm_probe(struct platform_device *pdev)
 	if (ret)
 		return dev_err_probe(dev, ret, "Failed to add mbox free action.\n");
 
-	acpm_setup_ops(acpm);
+	acpm->handle.ops = &exynos_acpm_driver_ops;
 
 	platform_set_drvdata(pdev, acpm);
 
diff --git a/drivers/mfd/sec-acpm.c b/drivers/mfd/sec-acpm.c
index 9e15b260b8df..3397d13d3b7f 100644
--- a/drivers/mfd/sec-acpm.c
+++ b/drivers/mfd/sec-acpm.c
@@ -391,7 +391,7 @@ static int sec_pmic_acpm_bus_write(void *context, const void *data,
 {
 	struct sec_pmic_acpm_bus_context *ctx = context;
 	struct acpm_handle *acpm = ctx->shared->acpm;
-	const struct acpm_pmic_ops *pmic_ops = &acpm->ops.pmic;
+	const struct acpm_pmic_ops *pmic_ops = &acpm->ops->pmic;
 	size_t val_count = count - BITS_TO_BYTES(ACPM_ADDR_BITS);
 	const u8 *d = data;
 	const u8 *vals = &d[BITS_TO_BYTES(ACPM_ADDR_BITS)];
@@ -411,7 +411,7 @@ static int sec_pmic_acpm_bus_read(void *context, const void *reg_buf, size_t reg
 {
 	struct sec_pmic_acpm_bus_context *ctx = context;
 	struct acpm_handle *acpm = ctx->shared->acpm;
-	const struct acpm_pmic_ops *pmic_ops = &acpm->ops.pmic;
+	const struct acpm_pmic_ops *pmic_ops = &acpm->ops->pmic;
 	const u8 *r = reg_buf;
 	u8 reg;
 
@@ -430,7 +430,7 @@ static int sec_pmic_acpm_bus_reg_update_bits(void *context, unsigned int reg, un
 {
 	struct sec_pmic_acpm_bus_context *ctx = context;
 	struct acpm_handle *acpm = ctx->shared->acpm;
-	const struct acpm_pmic_ops *pmic_ops = &acpm->ops.pmic;
+	const struct acpm_pmic_ops *pmic_ops = &acpm->ops->pmic;
 
 	return pmic_ops->update_reg(acpm, ctx->shared->acpm_chan_id, ctx->type, reg & 0xff,
 				    ctx->shared->speedy_channel, val, mask);
diff --git a/include/linux/firmware/samsung/exynos-acpm-protocol.h b/include/linux/firmware/samsung/exynos-acpm-protocol.h
index b206efa62be6..fbf1829b33db 100644
--- a/include/linux/firmware/samsung/exynos-acpm-protocol.h
+++ b/include/linux/firmware/samsung/exynos-acpm-protocol.h
@@ -42,10 +42,10 @@ struct acpm_ops {
 
 /**
  * struct acpm_handle - Reference to an initialized protocol instance
- * @ops:
+ * @ops:	pointer to the constant ACPM protocol operations.
  */
 struct acpm_handle {
-	struct acpm_ops ops;
+	const struct acpm_ops *ops;
 };
 
 struct device;

-- 
2.54.0.545.g6539524ca2-goog