[PATCH v3 0/5] ASoC / rpmsg / remoteproc / soc: qcom: Constify buffer passed to send functions

[PATCH v3 0/5] ASoC / rpmsg / remoteproc / soc: qcom: Constify buffer passed to send functions

[Krzysztof Kozlowski]

This got acks from Mathieu (remoteproc) and Mark (audio), so can we
funnel everything via Qualcomm remoteproc tree?

Dependencies / merging
======================
Entire patchset is one logical chain, all further patches depend on
previous ones, thus everything should be taken via same tree or shared
between trees with tags.  Probably everything should go via ASoC with
necessary acks.

Changes in v3:
- Subject fixes (Angelo)
- Tags
- Link to v2: https://patch.msgid.link/20260310-rpmsg-send-const-v2-0-0e94c5db9bf4@oss.qualcomm.com

Changes in v2:
- New patch #5: media: platform: mtk-mdp3: Constify buffer passed to mdp_vpu_sendmsg()
- Rebase, add acks.
- Link to v1: https://patch.msgid.link/20251130-rpmsg-send-const-v1-0-cb11c7e0a024@oss.qualcomm.com

Description
===========
The remoteproc and rpmsg send-like functions should not modify data
being sent, so buffer should be marked as pointer to const.  This is not
only self-documenting code but actually increases the actual safety and
clearly documents who is the owner of passed buffer.

Best regards,
Krzysztof

---
Krzysztof Kozlowski (5):
      remoteproc: mtk_scp_ipi: Constify buffer passed to scp_ipi_send()
      remoteproc: mtk_scp: Constify buffer passed to scp_send_ipi()
      rpmsg: Constify buffer passed to send API
      ASoC: qcom:: Constify GPR packet being send over GPR interface
      media: platform: mtk-mdp3: Constify buffer passed to mdp_vpu_sendmsg()

 .../media/platform/mediatek/mdp3/mtk-mdp3-vpu.c    |  2 +-
 drivers/remoteproc/mtk_scp.c                       |  2 +-
 drivers/remoteproc/mtk_scp_ipi.c                   |  2 +-
 drivers/rpmsg/mtk_rpmsg.c                          |  4 ++--
 drivers/rpmsg/qcom_glink_native.c                  | 13 +++++++-----
 drivers/rpmsg/qcom_smd.c                           | 10 +++++----
 drivers/rpmsg/rpmsg_core.c                         |  8 ++++----
 drivers/rpmsg/rpmsg_internal.h                     |  8 ++++----
 drivers/rpmsg/virtio_rpmsg_bus.c                   | 24 ++++++++++++----------
 drivers/soc/qcom/apr.c                             |  8 ++++----
 include/linux/remoteproc/mtk_scp.h                 |  2 +-
 include/linux/rpmsg.h                              | 17 +++++++--------
 include/linux/rpmsg/mtk_rpmsg.h                    |  2 +-
 include/linux/soc/qcom/apr.h                       |  4 ++--
 sound/soc/qcom/qdsp6/audioreach.c                  |  6 +++---
 sound/soc/qcom/qdsp6/audioreach.h                  |  4 ++--
 sound/soc/qcom/qdsp6/q6apm.c                       |  3 ++-
 sound/soc/qcom/qdsp6/q6apm.h                       |  2 +-
 18 files changed, 65 insertions(+), 56 deletions(-)
---
base-commit: 2360a9a195d2eae6f7d0cac2cbe920ae8a06c54f
change-id: 20251130-rpmsg-send-const-ae216a1fbd8f

Best regards,
-- 
Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>

[PATCH v3 1/5] remoteproc: mtk_scp_ipi: Constify buffer passed to scp_ipi_send()

[Krzysztof Kozlowski]

scp_ipi_send() should only send the passed buffer, without modifying its
contents, so mark pointer 'buf' as pointer to const.

Acked-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>
---

Patch necessary for the further patches, please keep with the rest.
---
 drivers/remoteproc/mtk_scp_ipi.c   | 2 +-
 include/linux/remoteproc/mtk_scp.h | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/remoteproc/mtk_scp_ipi.c b/drivers/remoteproc/mtk_scp_ipi.c
index 7a37e273b3af..ee2f1121411f 100644
--- a/drivers/remoteproc/mtk_scp_ipi.c
+++ b/drivers/remoteproc/mtk_scp_ipi.c
@@ -156,7 +156,7 @@ EXPORT_SYMBOL_GPL(scp_ipi_unlock);
  *
  * Return: 0 if sending data successfully, -error on error.
  **/
-int scp_ipi_send(struct mtk_scp *scp, u32 id, void *buf, unsigned int len,
+int scp_ipi_send(struct mtk_scp *scp, u32 id, const void *buf, unsigned int len,
 		 unsigned int wait)
 {
 	struct mtk_share_obj __iomem *send_obj = scp->send_buf;
diff --git a/include/linux/remoteproc/mtk_scp.h b/include/linux/remoteproc/mtk_scp.h
index 344ff41c22c7..4070537d6542 100644
--- a/include/linux/remoteproc/mtk_scp.h
+++ b/include/linux/remoteproc/mtk_scp.h
@@ -58,7 +58,7 @@ int scp_ipi_register(struct mtk_scp *scp, u32 id, scp_ipi_handler_t handler,
 		     void *priv);
 void scp_ipi_unregister(struct mtk_scp *scp, u32 id);
 
-int scp_ipi_send(struct mtk_scp *scp, u32 id, void *buf, unsigned int len,
+int scp_ipi_send(struct mtk_scp *scp, u32 id, const void *buf, unsigned int len,
 		 unsigned int wait);
 
 unsigned int scp_get_vdec_hw_capa(struct mtk_scp *scp);

-- 
2.51.0

[PATCH v3 2/5] remoteproc: mtk_scp: Constify buffer passed to scp_send_ipi()

[Krzysztof Kozlowski]

scp_send_ipi() should only send the passed buffer, without modifying its
contents, so mark pointer 'buf' as pointer to const.

Acked-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>
---

Patch necessary for the further patches, please keep with the rest.
---
 drivers/remoteproc/mtk_scp.c    | 2 +-
 include/linux/rpmsg/mtk_rpmsg.h | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/remoteproc/mtk_scp.c b/drivers/remoteproc/mtk_scp.c
index bb6f6a16d895..85a74c9ec521 100644
--- a/drivers/remoteproc/mtk_scp.c
+++ b/drivers/remoteproc/mtk_scp.c
@@ -1078,7 +1078,7 @@ static void scp_unregister_ipi(struct platform_device *pdev, u32 id)
 	scp_ipi_unregister(scp, id);
 }
 
-static int scp_send_ipi(struct platform_device *pdev, u32 id, void *buf,
+static int scp_send_ipi(struct platform_device *pdev, u32 id, const void *buf,
 			unsigned int len, unsigned int wait)
 {
 	struct mtk_scp *scp = platform_get_drvdata(pdev);
diff --git a/include/linux/rpmsg/mtk_rpmsg.h b/include/linux/rpmsg/mtk_rpmsg.h
index 363b60178040..badcbc89917f 100644
--- a/include/linux/rpmsg/mtk_rpmsg.h
+++ b/include/linux/rpmsg/mtk_rpmsg.h
@@ -25,7 +25,7 @@ struct mtk_rpmsg_info {
 			    ipi_handler_t handler, void *priv);
 	void (*unregister_ipi)(struct platform_device *pdev, u32 id);
 	int (*send_ipi)(struct platform_device *pdev, u32 id,
-			void *buf, unsigned int len, unsigned int wait);
+			const void *buf, unsigned int len, unsigned int wait);
 	int ns_ipi_id;
 };
 

-- 
2.51.0

[PATCH v3 3/5] rpmsg: Constify buffer passed to send API

[Krzysztof Kozlowski]

The rpmsg_send(), rpmsg_sendto() and other variants of sending
interfaces should only send the passed data, without modifying its
contents, so mark pointer 'data' as pointer to const.  All users of this
interface already follow this approach, so only the function
declarations have to be updated.

Acked-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>
---

Patch necessary for the further patches, please keep with the rest.
---
 drivers/rpmsg/mtk_rpmsg.c         |  4 ++--
 drivers/rpmsg/qcom_glink_native.c | 13 ++++++++-----
 drivers/rpmsg/qcom_smd.c          | 10 ++++++----
 drivers/rpmsg/rpmsg_core.c        |  8 ++++----
 drivers/rpmsg/rpmsg_internal.h    |  8 ++++----
 drivers/rpmsg/virtio_rpmsg_bus.c  | 24 +++++++++++++-----------
 include/linux/rpmsg.h             | 17 +++++++++--------
 7 files changed, 46 insertions(+), 38 deletions(-)

diff --git a/drivers/rpmsg/mtk_rpmsg.c b/drivers/rpmsg/mtk_rpmsg.c
index 0e03c5336609..1b670ed54cfa 100644
--- a/drivers/rpmsg/mtk_rpmsg.c
+++ b/drivers/rpmsg/mtk_rpmsg.c
@@ -135,7 +135,7 @@ static void mtk_rpmsg_destroy_ept(struct rpmsg_endpoint *ept)
 	kref_put(&ept->refcount, __mtk_ept_release);
 }
 
-static int mtk_rpmsg_send(struct rpmsg_endpoint *ept, void *data, int len)
+static int mtk_rpmsg_send(struct rpmsg_endpoint *ept, const void *data, int len)
 {
 	struct mtk_rpmsg_rproc_subdev *mtk_subdev =
 		to_mtk_rpmsg_endpoint(ept)->mtk_subdev;
@@ -144,7 +144,7 @@ static int mtk_rpmsg_send(struct rpmsg_endpoint *ept, void *data, int len)
 					  len, 0);
 }
 
-static int mtk_rpmsg_trysend(struct rpmsg_endpoint *ept, void *data, int len)
+static int mtk_rpmsg_trysend(struct rpmsg_endpoint *ept, const void *data, int len)
 {
 	struct mtk_rpmsg_rproc_subdev *mtk_subdev =
 		to_mtk_rpmsg_endpoint(ept)->mtk_subdev;
diff --git a/drivers/rpmsg/qcom_glink_native.c b/drivers/rpmsg/qcom_glink_native.c
index 9ef17c2e45b0..401a4ece0c97 100644
--- a/drivers/rpmsg/qcom_glink_native.c
+++ b/drivers/rpmsg/qcom_glink_native.c
@@ -1474,7 +1474,7 @@ static int qcom_glink_request_intent(struct qcom_glink *glink,
 }
 
 static int __qcom_glink_send(struct glink_channel *channel,
-			     void *data, int len, bool wait)
+			     const void *data, int len, bool wait)
 {
 	struct qcom_glink *glink = channel->glink;
 	struct glink_core_rx_intent *intent = NULL;
@@ -1553,28 +1553,31 @@ static int __qcom_glink_send(struct glink_channel *channel,
 	return 0;
 }
 
-static int qcom_glink_send(struct rpmsg_endpoint *ept, void *data, int len)
+static int qcom_glink_send(struct rpmsg_endpoint *ept, const void *data, int len)
 {
 	struct glink_channel *channel = to_glink_channel(ept);
 
 	return __qcom_glink_send(channel, data, len, true);
 }
 
-static int qcom_glink_trysend(struct rpmsg_endpoint *ept, void *data, int len)
+static int qcom_glink_trysend(struct rpmsg_endpoint *ept, const void *data,
+			      int len)
 {
 	struct glink_channel *channel = to_glink_channel(ept);
 
 	return __qcom_glink_send(channel, data, len, false);
 }
 
-static int qcom_glink_sendto(struct rpmsg_endpoint *ept, void *data, int len, u32 dst)
+static int qcom_glink_sendto(struct rpmsg_endpoint *ept, const void *data,
+			     int len, u32 dst)
 {
 	struct glink_channel *channel = to_glink_channel(ept);
 
 	return __qcom_glink_send(channel, data, len, true);
 }
 
-static int qcom_glink_trysendto(struct rpmsg_endpoint *ept, void *data, int len, u32 dst)
+static int qcom_glink_trysendto(struct rpmsg_endpoint *ept, const void *data,
+				int len, u32 dst)
 {
 	struct glink_channel *channel = to_glink_channel(ept);
 
diff --git a/drivers/rpmsg/qcom_smd.c b/drivers/rpmsg/qcom_smd.c
index e1eb450f4fea..3ac863f400ec 100644
--- a/drivers/rpmsg/qcom_smd.c
+++ b/drivers/rpmsg/qcom_smd.c
@@ -960,28 +960,30 @@ static void qcom_smd_destroy_ept(struct rpmsg_endpoint *ept)
 	kref_put(&ept->refcount, __ept_release);
 }
 
-static int qcom_smd_send(struct rpmsg_endpoint *ept, void *data, int len)
+static int qcom_smd_send(struct rpmsg_endpoint *ept, const void *data, int len)
 {
 	struct qcom_smd_endpoint *qsept = to_smd_endpoint(ept);
 
 	return __qcom_smd_send(qsept->qsch, data, len, true);
 }
 
-static int qcom_smd_trysend(struct rpmsg_endpoint *ept, void *data, int len)
+static int qcom_smd_trysend(struct rpmsg_endpoint *ept, const void *data, int len)
 {
 	struct qcom_smd_endpoint *qsept = to_smd_endpoint(ept);
 
 	return __qcom_smd_send(qsept->qsch, data, len, false);
 }
 
-static int qcom_smd_sendto(struct rpmsg_endpoint *ept, void *data, int len, u32 dst)
+static int qcom_smd_sendto(struct rpmsg_endpoint *ept, const void *data, int len,
+			   u32 dst)
 {
 	struct qcom_smd_endpoint *qsept = to_smd_endpoint(ept);
 
 	return __qcom_smd_send(qsept->qsch, data, len, true);
 }
 
-static int qcom_smd_trysendto(struct rpmsg_endpoint *ept, void *data, int len, u32 dst)
+static int qcom_smd_trysendto(struct rpmsg_endpoint *ept, const void *data,
+			      int len, u32 dst)
 {
 	struct qcom_smd_endpoint *qsept = to_smd_endpoint(ept);
 
diff --git a/drivers/rpmsg/rpmsg_core.c b/drivers/rpmsg/rpmsg_core.c
index 96964745065b..2f9444d1f194 100644
--- a/drivers/rpmsg/rpmsg_core.c
+++ b/drivers/rpmsg/rpmsg_core.c
@@ -153,7 +153,7 @@ EXPORT_SYMBOL(rpmsg_destroy_ept);
  *
  * Return: 0 on success and an appropriate error value on failure.
  */
-int rpmsg_send(struct rpmsg_endpoint *ept, void *data, int len)
+int rpmsg_send(struct rpmsg_endpoint *ept, const void *data, int len)
 {
 	if (WARN_ON(!ept))
 		return -EINVAL;
@@ -182,7 +182,7 @@ EXPORT_SYMBOL(rpmsg_send);
  *
  * Return: 0 on success and an appropriate error value on failure.
  */
-int rpmsg_sendto(struct rpmsg_endpoint *ept, void *data, int len, u32 dst)
+int rpmsg_sendto(struct rpmsg_endpoint *ept, const void *data, int len, u32 dst)
 {
 	if (WARN_ON(!ept))
 		return -EINVAL;
@@ -210,7 +210,7 @@ EXPORT_SYMBOL(rpmsg_sendto);
  *
  * Return: 0 on success and an appropriate error value on failure.
  */
-int rpmsg_trysend(struct rpmsg_endpoint *ept, void *data, int len)
+int rpmsg_trysend(struct rpmsg_endpoint *ept, const void *data, int len)
 {
 	if (WARN_ON(!ept))
 		return -EINVAL;
@@ -238,7 +238,7 @@ EXPORT_SYMBOL(rpmsg_trysend);
  *
  * Return: 0 on success and an appropriate error value on failure.
  */
-int rpmsg_trysendto(struct rpmsg_endpoint *ept, void *data, int len, u32 dst)
+int rpmsg_trysendto(struct rpmsg_endpoint *ept, const void *data, int len, u32 dst)
 {
 	if (WARN_ON(!ept))
 		return -EINVAL;
diff --git a/drivers/rpmsg/rpmsg_internal.h b/drivers/rpmsg/rpmsg_internal.h
index 397e4926bd02..a8b7065fd165 100644
--- a/drivers/rpmsg/rpmsg_internal.h
+++ b/drivers/rpmsg/rpmsg_internal.h
@@ -63,11 +63,11 @@ struct rpmsg_device_ops {
 struct rpmsg_endpoint_ops {
 	void (*destroy_ept)(struct rpmsg_endpoint *ept);
 
-	int (*send)(struct rpmsg_endpoint *ept, void *data, int len);
-	int (*sendto)(struct rpmsg_endpoint *ept, void *data, int len, u32 dst);
+	int (*send)(struct rpmsg_endpoint *ept, const void *data, int len);
+	int (*sendto)(struct rpmsg_endpoint *ept, const void *data, int len, u32 dst);
 
-	int (*trysend)(struct rpmsg_endpoint *ept, void *data, int len);
-	int (*trysendto)(struct rpmsg_endpoint *ept, void *data, int len, u32 dst);
+	int (*trysend)(struct rpmsg_endpoint *ept, const void *data, int len);
+	int (*trysendto)(struct rpmsg_endpoint *ept, const void *data, int len, u32 dst);
 	__poll_t (*poll)(struct rpmsg_endpoint *ept, struct file *filp,
 			     poll_table *wait);
 	int (*set_flow_control)(struct rpmsg_endpoint *ept, bool pause, u32 dst);
diff --git a/drivers/rpmsg/virtio_rpmsg_bus.c b/drivers/rpmsg/virtio_rpmsg_bus.c
index 8d9e2b4dc7c1..5ae15111fb4f 100644
--- a/drivers/rpmsg/virtio_rpmsg_bus.c
+++ b/drivers/rpmsg/virtio_rpmsg_bus.c
@@ -136,11 +136,12 @@ struct virtio_rpmsg_channel {
 #define RPMSG_RESERVED_ADDRESSES	(1024)
 
 static void virtio_rpmsg_destroy_ept(struct rpmsg_endpoint *ept);
-static int virtio_rpmsg_send(struct rpmsg_endpoint *ept, void *data, int len);
-static int virtio_rpmsg_sendto(struct rpmsg_endpoint *ept, void *data, int len,
-			       u32 dst);
-static int virtio_rpmsg_trysend(struct rpmsg_endpoint *ept, void *data, int len);
-static int virtio_rpmsg_trysendto(struct rpmsg_endpoint *ept, void *data,
+static int virtio_rpmsg_send(struct rpmsg_endpoint *ept, const void *data, int len);
+static int virtio_rpmsg_sendto(struct rpmsg_endpoint *ept, const void *data,
+			       int len, u32 dst);
+static int virtio_rpmsg_trysend(struct rpmsg_endpoint *ept, const void *data,
+				int len);
+static int virtio_rpmsg_trysendto(struct rpmsg_endpoint *ept, const void *data,
 				  int len, u32 dst);
 static __poll_t virtio_rpmsg_poll(struct rpmsg_endpoint *ept, struct file *filp,
 				  poll_table *wait);
@@ -490,7 +491,7 @@ static void *get_a_tx_buf(struct virtproc_info *vrp)
  */
 static int rpmsg_send_offchannel_raw(struct rpmsg_device *rpdev,
 				     u32 src, u32 dst,
-				     void *data, int len, bool wait)
+				     const void *data, int len, bool wait)
 {
 	struct virtio_rpmsg_channel *vch = to_virtio_rpmsg_channel(rpdev);
 	struct virtproc_info *vrp = vch->vrp;
@@ -580,7 +581,7 @@ static int rpmsg_send_offchannel_raw(struct rpmsg_device *rpdev,
 	return err;
 }
 
-static int virtio_rpmsg_send(struct rpmsg_endpoint *ept, void *data, int len)
+static int virtio_rpmsg_send(struct rpmsg_endpoint *ept, const void *data, int len)
 {
 	struct rpmsg_device *rpdev = ept->rpdev;
 	u32 src = ept->addr, dst = rpdev->dst;
@@ -588,8 +589,8 @@ static int virtio_rpmsg_send(struct rpmsg_endpoint *ept, void *data, int len)
 	return rpmsg_send_offchannel_raw(rpdev, src, dst, data, len, true);
 }
 
-static int virtio_rpmsg_sendto(struct rpmsg_endpoint *ept, void *data, int len,
-			       u32 dst)
+static int virtio_rpmsg_sendto(struct rpmsg_endpoint *ept, const void *data,
+			       int len, u32 dst)
 {
 	struct rpmsg_device *rpdev = ept->rpdev;
 	u32 src = ept->addr;
@@ -597,7 +598,8 @@ static int virtio_rpmsg_sendto(struct rpmsg_endpoint *ept, void *data, int len,
 	return rpmsg_send_offchannel_raw(rpdev, src, dst, data, len, true);
 }
 
-static int virtio_rpmsg_trysend(struct rpmsg_endpoint *ept, void *data, int len)
+static int virtio_rpmsg_trysend(struct rpmsg_endpoint *ept, const void *data,
+				int len)
 {
 	struct rpmsg_device *rpdev = ept->rpdev;
 	u32 src = ept->addr, dst = rpdev->dst;
@@ -605,7 +607,7 @@ static int virtio_rpmsg_trysend(struct rpmsg_endpoint *ept, void *data, int len)
 	return rpmsg_send_offchannel_raw(rpdev, src, dst, data, len, false);
 }
 
-static int virtio_rpmsg_trysendto(struct rpmsg_endpoint *ept, void *data,
+static int virtio_rpmsg_trysendto(struct rpmsg_endpoint *ept, const void *data,
 				  int len, u32 dst)
 {
 	struct rpmsg_device *rpdev = ept->rpdev;
diff --git a/include/linux/rpmsg.h b/include/linux/rpmsg.h
index fb7ab9165645..83266ce14642 100644
--- a/include/linux/rpmsg.h
+++ b/include/linux/rpmsg.h
@@ -182,11 +182,11 @@ struct rpmsg_endpoint *rpmsg_create_ept(struct rpmsg_device *,
 					rpmsg_rx_cb_t cb, void *priv,
 					struct rpmsg_channel_info chinfo);
 
-int rpmsg_send(struct rpmsg_endpoint *ept, void *data, int len);
-int rpmsg_sendto(struct rpmsg_endpoint *ept, void *data, int len, u32 dst);
+int rpmsg_send(struct rpmsg_endpoint *ept, const void *data, int len);
+int rpmsg_sendto(struct rpmsg_endpoint *ept, const void *data, int len, u32 dst);
 
-int rpmsg_trysend(struct rpmsg_endpoint *ept, void *data, int len);
-int rpmsg_trysendto(struct rpmsg_endpoint *ept, void *data, int len, u32 dst);
+int rpmsg_trysend(struct rpmsg_endpoint *ept, const void *data, int len);
+int rpmsg_trysendto(struct rpmsg_endpoint *ept, const void *data, int len, u32 dst);
 
 __poll_t rpmsg_poll(struct rpmsg_endpoint *ept, struct file *filp,
 			poll_table *wait);
@@ -249,7 +249,7 @@ static inline struct rpmsg_endpoint *rpmsg_create_ept(struct rpmsg_device *rpdev
 	return NULL;
 }
 
-static inline int rpmsg_send(struct rpmsg_endpoint *ept, void *data, int len)
+static inline int rpmsg_send(struct rpmsg_endpoint *ept, const void *data, int len)
 {
 	/* This shouldn't be possible */
 	WARN_ON(1);
@@ -257,7 +257,7 @@ static inline int rpmsg_send(struct rpmsg_endpoint *ept, void *data, int len)
 	return -ENXIO;
 }
 
-static inline int rpmsg_sendto(struct rpmsg_endpoint *ept, void *data, int len,
+static inline int rpmsg_sendto(struct rpmsg_endpoint *ept, const void *data, int len,
 			       u32 dst)
 {
 	/* This shouldn't be possible */
@@ -267,7 +267,8 @@ static inline int rpmsg_sendto(struct rpmsg_endpoint *ept, void *data, int len,
 
 }
 
-static inline int rpmsg_trysend(struct rpmsg_endpoint *ept, void *data, int len)
+static inline int rpmsg_trysend(struct rpmsg_endpoint *ept, const void *data,
+				int len)
 {
 	/* This shouldn't be possible */
 	WARN_ON(1);
@@ -275,7 +276,7 @@ static inline int rpmsg_trysend(struct rpmsg_endpoint *ept, void *data, int len)
 	return -ENXIO;
 }
 
-static inline int rpmsg_trysendto(struct rpmsg_endpoint *ept, void *data,
+static inline int rpmsg_trysendto(struct rpmsg_endpoint *ept, const void *data,
 				  int len, u32 dst)
 {
 	/* This shouldn't be possible */

-- 
2.51.0

[PATCH v3 4/5] ASoC: qcom:: Constify GPR packet being send over GPR interface

[Krzysztof Kozlowski]

gpr_send_pkt() and pkt_router_send_svc_pkt() only send the GPR packet
they receive, without any need to actually modify it, so mark the
pointer to GPR packet as pointer to const for code safety and code
self-documentation.  Several usersof this interface can follow up and
also operate on pointer to const.

Acked-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Acked-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>
---

Depends on previous patches.
---
 drivers/soc/qcom/apr.c            | 8 ++++----
 include/linux/soc/qcom/apr.h      | 4 ++--
 sound/soc/qcom/qdsp6/audioreach.c | 6 +++---
 sound/soc/qcom/qdsp6/audioreach.h | 4 ++--
 sound/soc/qcom/qdsp6/q6apm.c      | 3 ++-
 sound/soc/qcom/qdsp6/q6apm.h      | 2 +-
 6 files changed, 14 insertions(+), 13 deletions(-)

diff --git a/drivers/soc/qcom/apr.c b/drivers/soc/qcom/apr.c
index 78e72379a6e0..ea7f83916d8d 100644
--- a/drivers/soc/qcom/apr.c
+++ b/drivers/soc/qcom/apr.c
@@ -123,10 +123,10 @@ gpr_port_t *gpr_alloc_port(struct apr_device *gdev, struct device *dev,
 }
 EXPORT_SYMBOL_GPL(gpr_alloc_port);
 
-static int pkt_router_send_svc_pkt(struct pkt_router_svc *svc, struct gpr_pkt *pkt)
+static int pkt_router_send_svc_pkt(struct pkt_router_svc *svc, const struct gpr_pkt *pkt)
 {
 	struct packet_router *pr = svc->pr;
-	struct gpr_hdr *hdr;
+	const struct gpr_hdr *hdr;
 	unsigned long flags;
 	int ret;
 
@@ -139,13 +139,13 @@ static int pkt_router_send_svc_pkt(struct pkt_router_svc *svc, struct gpr_pkt *p
 	return ret ? ret : hdr->pkt_size;
 }
 
-int gpr_send_pkt(struct apr_device *gdev, struct gpr_pkt *pkt)
+int gpr_send_pkt(struct apr_device *gdev, const struct gpr_pkt *pkt)
 {
 	return pkt_router_send_svc_pkt(&gdev->svc, pkt);
 }
 EXPORT_SYMBOL_GPL(gpr_send_pkt);
 
-int gpr_send_port_pkt(gpr_port_t *port, struct gpr_pkt *pkt)
+int gpr_send_port_pkt(gpr_port_t *port, const struct gpr_pkt *pkt)
 {
 	return pkt_router_send_svc_pkt(port, pkt);
 }
diff --git a/include/linux/soc/qcom/apr.h b/include/linux/soc/qcom/apr.h
index 6e1b1202e818..58fa1df96347 100644
--- a/include/linux/soc/qcom/apr.h
+++ b/include/linux/soc/qcom/apr.h
@@ -191,7 +191,7 @@ int apr_send_pkt(struct apr_device *adev, struct apr_pkt *pkt);
 gpr_port_t *gpr_alloc_port(gpr_device_t *gdev, struct device *dev,
 				gpr_port_cb cb, void *priv);
 void gpr_free_port(gpr_port_t *port);
-int gpr_send_port_pkt(gpr_port_t *port, struct gpr_pkt *pkt);
-int gpr_send_pkt(gpr_device_t *gdev, struct gpr_pkt *pkt);
+int gpr_send_port_pkt(gpr_port_t *port, const struct gpr_pkt *pkt);
+int gpr_send_pkt(gpr_device_t *gdev, const struct gpr_pkt *pkt);
 
 #endif /* __QCOM_APR_H_ */
diff --git a/sound/soc/qcom/qdsp6/audioreach.c b/sound/soc/qcom/qdsp6/audioreach.c
index 241c3b4479c6..c84e098230c6 100644
--- a/sound/soc/qcom/qdsp6/audioreach.c
+++ b/sound/soc/qcom/qdsp6/audioreach.c
@@ -579,10 +579,10 @@ EXPORT_SYMBOL_GPL(audioreach_alloc_graph_pkt);
 int audioreach_send_cmd_sync(struct device *dev, gpr_device_t *gdev,
 			     struct gpr_ibasic_rsp_result_t *result, struct mutex *cmd_lock,
 			     gpr_port_t *port, wait_queue_head_t *cmd_wait,
-			     struct gpr_pkt *pkt, uint32_t rsp_opcode)
+			     const struct gpr_pkt *pkt, uint32_t rsp_opcode)
 {
 
-	struct gpr_hdr *hdr = &pkt->hdr;
+	const struct gpr_hdr *hdr = &pkt->hdr;
 	int rc;
 
 	mutex_lock(cmd_lock);
@@ -622,7 +622,7 @@ int audioreach_send_cmd_sync(struct device *dev, gpr_device_t *gdev,
 }
 EXPORT_SYMBOL_GPL(audioreach_send_cmd_sync);
 
-int audioreach_graph_send_cmd_sync(struct q6apm_graph *graph, struct gpr_pkt *pkt,
+int audioreach_graph_send_cmd_sync(struct q6apm_graph *graph, const struct gpr_pkt *pkt,
 				   uint32_t rsp_opcode)
 {
 
diff --git a/sound/soc/qcom/qdsp6/audioreach.h b/sound/soc/qcom/qdsp6/audioreach.h
index 89f172aab8c0..6262b9251440 100644
--- a/sound/soc/qcom/qdsp6/audioreach.h
+++ b/sound/soc/qcom/qdsp6/audioreach.h
@@ -844,8 +844,8 @@ int audioreach_map_memory_regions(struct q6apm_graph *graph,
 				  bool is_contiguous);
 int audioreach_send_cmd_sync(struct device *dev, gpr_device_t *gdev, struct gpr_ibasic_rsp_result_t *result,
 			     struct mutex *cmd_lock, gpr_port_t *port, wait_queue_head_t *cmd_wait,
-			     struct gpr_pkt *pkt, uint32_t rsp_opcode);
-int audioreach_graph_send_cmd_sync(struct q6apm_graph *graph, struct gpr_pkt *pkt,
+			     const struct gpr_pkt *pkt, uint32_t rsp_opcode);
+int audioreach_graph_send_cmd_sync(struct q6apm_graph *graph, const struct gpr_pkt *pkt,
 				   uint32_t rsp_opcode);
 int audioreach_set_media_format(struct q6apm_graph *graph,
 				const struct audioreach_module *module,
diff --git a/sound/soc/qcom/qdsp6/q6apm.c b/sound/soc/qcom/qdsp6/q6apm.c
index 44841fde3856..3527ad1acbca 100644
--- a/sound/soc/qcom/qdsp6/q6apm.c
+++ b/sound/soc/qcom/qdsp6/q6apm.c
@@ -29,7 +29,8 @@ struct apm_graph_mgmt_cmd {
 
 static struct q6apm *g_apm;
 
-int q6apm_send_cmd_sync(struct q6apm *apm, struct gpr_pkt *pkt, uint32_t rsp_opcode)
+int q6apm_send_cmd_sync(struct q6apm *apm, const struct gpr_pkt *pkt,
+			uint32_t rsp_opcode)
 {
 	gpr_device_t *gdev = apm->gdev;
 
diff --git a/sound/soc/qcom/qdsp6/q6apm.h b/sound/soc/qcom/qdsp6/q6apm.h
index 7ce08b401e31..a39f6046f886 100644
--- a/sound/soc/qcom/qdsp6/q6apm.h
+++ b/sound/soc/qcom/qdsp6/q6apm.h
@@ -138,7 +138,7 @@ int q6apm_map_memory_regions(struct q6apm_graph *graph,
 int q6apm_unmap_memory_regions(struct q6apm_graph *graph,
 			       unsigned int dir);
 /* Helpers */
-int q6apm_send_cmd_sync(struct q6apm *apm, struct gpr_pkt *pkt,
+int q6apm_send_cmd_sync(struct q6apm *apm, const struct gpr_pkt *pkt,
 			uint32_t rsp_opcode);
 
 /* Callback for graph specific */

-- 
2.51.0

[PATCH v3 5/5] media: platform: mtk-mdp3: Constify buffer passed to mdp_vpu_sendmsg()

[Krzysztof Kozlowski]

mdp_vpu_sendmsg() passes the buffer to scp_ipi_send(), which takes now
pointer to const, so adjust this interface as well for increased code
safety and code readability.

Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>
---

Depends on the first patch.
---
 drivers/media/platform/mediatek/mdp3/mtk-mdp3-vpu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/media/platform/mediatek/mdp3/mtk-mdp3-vpu.c b/drivers/media/platform/mediatek/mdp3/mtk-mdp3-vpu.c
index fae3e1ad2df7..67f3001153ae 100644
--- a/drivers/media/platform/mediatek/mdp3/mtk-mdp3-vpu.c
+++ b/drivers/media/platform/mediatek/mdp3/mtk-mdp3-vpu.c
@@ -163,7 +163,7 @@ void mdp_vpu_unregister(struct mdp_dev *mdp)
 }
 
 static int mdp_vpu_sendmsg(struct mdp_vpu_dev *vpu, enum scp_ipi_id id,
-			   void *buf, unsigned int len)
+			   const void *buf, unsigned int len)
 {
 	struct mdp_dev *mdp = vpu_to_mdp(vpu);
 	unsigned int t = MDP_VPU_MESSAGE_TIMEOUT;

-- 
2.51.0

Re: [PATCH v3 0/5] ASoC / rpmsg / remoteproc / soc: qcom: Constify buffer passed to send functions

[Mathieu Poirier]

On Tue, 17 Mar 2026 at 06:37, Krzysztof Kozlowski
<krzysztof.kozlowski@oss.qualcomm.com> wrote:
>
> This got acks from Mathieu (remoteproc) and Mark (audio), so can we
> funnel everything via Qualcomm remoteproc tree?
>

I'm good with that.

> Dependencies / merging
> ======================
> Entire patchset is one logical chain, all further patches depend on
> previous ones, thus everything should be taken via same tree or shared
> between trees with tags.  Probably everything should go via ASoC with
> necessary acks.
>
> Changes in v3:
> - Subject fixes (Angelo)
> - Tags
> - Link to v2: https://patch.msgid.link/20260310-rpmsg-send-const-v2-0-0e94c5db9bf4@oss.qualcomm.com
>
> Changes in v2:
> - New patch #5: media: platform: mtk-mdp3: Constify buffer passed to mdp_vpu_sendmsg()
> - Rebase, add acks.
> - Link to v1: https://patch.msgid.link/20251130-rpmsg-send-const-v1-0-cb11c7e0a024@oss.qualcomm.com
>
> Description
> ===========
> The remoteproc and rpmsg send-like functions should not modify data
> being sent, so buffer should be marked as pointer to const.  This is not
> only self-documenting code but actually increases the actual safety and
> clearly documents who is the owner of passed buffer.
>
> Best regards,
> Krzysztof
>
> ---
> Krzysztof Kozlowski (5):
>       remoteproc: mtk_scp_ipi: Constify buffer passed to scp_ipi_send()
>       remoteproc: mtk_scp: Constify buffer passed to scp_send_ipi()
>       rpmsg: Constify buffer passed to send API
>       ASoC: qcom:: Constify GPR packet being send over GPR interface
>       media: platform: mtk-mdp3: Constify buffer passed to mdp_vpu_sendmsg()
>
>  .../media/platform/mediatek/mdp3/mtk-mdp3-vpu.c    |  2 +-
>  drivers/remoteproc/mtk_scp.c                       |  2 +-
>  drivers/remoteproc/mtk_scp_ipi.c                   |  2 +-
>  drivers/rpmsg/mtk_rpmsg.c                          |  4 ++--
>  drivers/rpmsg/qcom_glink_native.c                  | 13 +++++++-----
>  drivers/rpmsg/qcom_smd.c                           | 10 +++++----
>  drivers/rpmsg/rpmsg_core.c                         |  8 ++++----
>  drivers/rpmsg/rpmsg_internal.h                     |  8 ++++----
>  drivers/rpmsg/virtio_rpmsg_bus.c                   | 24 ++++++++++++----------
>  drivers/soc/qcom/apr.c                             |  8 ++++----
>  include/linux/remoteproc/mtk_scp.h                 |  2 +-
>  include/linux/rpmsg.h                              | 17 +++++++--------
>  include/linux/rpmsg/mtk_rpmsg.h                    |  2 +-
>  include/linux/soc/qcom/apr.h                       |  4 ++--
>  sound/soc/qcom/qdsp6/audioreach.c                  |  6 +++---
>  sound/soc/qcom/qdsp6/audioreach.h                  |  4 ++--
>  sound/soc/qcom/qdsp6/q6apm.c                       |  3 ++-
>  sound/soc/qcom/qdsp6/q6apm.h                       |  2 +-
>  18 files changed, 65 insertions(+), 56 deletions(-)
> ---
> base-commit: 2360a9a195d2eae6f7d0cac2cbe920ae8a06c54f
> change-id: 20251130-rpmsg-send-const-ae216a1fbd8f
>
> Best regards,
> --
> Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>
>