[PATCH v6 4/5] i3c: master: Validate GET CCC payload length and retry Direct GET once

[tze . yee . ng]

From: Adrian Ng Ho Yin <adrian.ho.yin.ng@xxxxxxxxxx>

Add retries to struct i3c_ccc_cmd. Validate GET payload length in
i3c_master_send_ccc_cmd_locked() after a successful transfer.

Retry failed Direct GET CCCs up to cmd->retries times when the driver
reports failure or an I3C error; validation failures are not retried.
SET CCCs are not retried by default.

Signed-off-by: Adrian Ng Ho Yin <adrian.ho.yin.ng@xxxxxxxxxx>
Signed-off-by: Tze Yee Ng <tze.yee.ng@xxxxxxxxxx>
---
Changes in v5:
- Split from v4 patch 3/3: retry and strict validation only; optional_bytes
  moved to patch 5/5.
- Validate GET payload length after a successful transfer.
- Retry failed Direct GET CCCs when the driver reports failure or an I3C
  error; validation failures are not retried.

Changes in v4:
- Add optional_bytes to struct i3c_ccc_cmd_payload and retries to
  struct i3c_ccc_cmd (default I3C_CCC_RETRIES for GET, 0 for SET).
- Replace CCC-ID-specific payload checks with generic validation using
  actual_len, len, and optional_bytes.
- GETMRL and GETMXDS set optional_bytes at the call site instead of
  hardcoding lengths in the core.
- Retry failed Direct GET CCCs on any error up to cmd->retries times,
  per I3C spec Direct GET single-retry model (§5.1.9.2.3); drop M0/M2-
  gated retry logic.
- Drop req_lens save/restore and the stack/kmalloc bookkeeping for
  payload.len.
- Update I3C master drivers (SVC, Cadence, ADI, Renesas, MIPI HCI) to
  populate actual_len on successful GET transfers.
- Use actual_len in getmrl_locked(), getmwl_locked(), getmxds_locked(),
  and gethdrcap_locked().
---
 drivers/i3c/master.c    | 59 ++++++++++++++++++++++++++++++++++++++---
 include/linux/i3c/ccc.h |  5 ++++
 2 files changed, 60 insertions(+), 4 deletions(-)

diff --git a/drivers/i3c/master.c b/drivers/i3c/master.c
index 037b3b980717..3b6d3ecd9d12 100644
--- a/drivers/i3c/master.c
+++ b/drivers/i3c/master.c
@@ -915,17 +915,46 @@ static void i3c_ccc_cmd_dest_cleanup(struct i3c_ccc_cmd_dest *dest)
 	kfree(dest->payload.data);
 }
 
-static void i3c_ccc_cmd_init(struct i3c_ccc_cmd *cmd, bool rnw, u8 id,
-			     struct i3c_ccc_cmd_dest *dests,
-			     unsigned int ndests)
+static void i3c_ccc_cmd_init_retries(struct i3c_ccc_cmd *cmd, bool rnw, u8 id,
+				     struct i3c_ccc_cmd_dest *dests,
+				     unsigned int ndests, unsigned int retries)
 {
 	cmd->rnw = rnw ? 1 : 0;
 	cmd->id = id;
 	cmd->dests = dests;
 	cmd->ndests = ndests;
+	cmd->retries = retries;
 	cmd->err = I3C_ERROR_UNKNOWN;
 }
 
+static void i3c_ccc_cmd_init(struct i3c_ccc_cmd *cmd, bool rnw, u8 id,
+			     struct i3c_ccc_cmd_dest *dests,
+			     unsigned int ndests)
+{
+	i3c_ccc_cmd_init_retries(cmd, rnw, id, dests, ndests,
+				 rnw ? I3C_CCC_RETRIES : 0);
+}
+
+static int i3c_ccc_validate_payload_len(struct i3c_ccc_cmd *cmd)
+{
+	unsigned int i;
+
+	if (!cmd->rnw)
+		return 0;
+
+	for (i = 0; i < cmd->ndests; i++) {
+		struct i3c_ccc_cmd_payload *p = &cmd->dests[i].payload;
+
+		if (p->actual_len > p->len)
+			return -EIO;
+
+		if (p->len && p->actual_len != p->len)
+			return -EIO;
+	}
+
+	return 0;
+}
+
 /**
  * i3c_master_send_ccc_cmd_locked() - send a CCC (Common Command Codes)
  * @master: master used to send frames on the bus
@@ -937,6 +966,9 @@ static void i3c_ccc_cmd_init(struct i3c_ccc_cmd *cmd, bool rnw, u8 id,
 static int i3c_master_send_ccc_cmd_locked(struct i3c_master_controller *master,
 					  struct i3c_ccc_cmd *cmd)
 {
+	unsigned int attempt, max_attempts;
+	int ret;
+
 	if (!cmd || !master)
 		return -EINVAL;
 
@@ -954,7 +986,25 @@ static int i3c_master_send_ccc_cmd_locked(struct i3c_master_controller *master,
 	    !master->ops->supports_ccc_cmd(master, cmd))
 		return -EOPNOTSUPP;
 
-	return master->ops->send_ccc_cmd(master, cmd);
+	max_attempts = cmd->retries + 1;
+	ret = -EIO;
+	for (attempt = 0; attempt < max_attempts; attempt++) {
+		unsigned int i;
+
+		if (cmd->rnw)
+			for (i = 0; i < cmd->ndests; i++)
+				cmd->dests[i].payload.actual_len = 0;
+
+		cmd->err = I3C_ERROR_UNKNOWN;
+		ret = master->ops->send_ccc_cmd(master, cmd);
+		if (!ret && cmd->err == I3C_ERROR_UNKNOWN)
+			break;
+	}
+
+	if (!ret)
+		ret = i3c_ccc_validate_payload_len(cmd);
+
+	return ret;
 }
 
 static struct i2c_dev_desc *
@@ -1372,6 +1422,7 @@ static int i3c_master_getmxds_locked(struct i3c_master_controller *master,
 		 * while expecting shorter length from this CCC command.
 		 */
 		dest.payload.len -= 3;
+		i3c_ccc_cmd_init(&cmd, true, I3C_CCC_GETMXDS, &dest, 1);
 		ret = i3c_master_send_ccc_cmd_locked(master, &cmd);
 		if (ret)
 			goto out;
diff --git a/include/linux/i3c/ccc.h b/include/linux/i3c/ccc.h
index d8052949e57e..2506d83b8255 100644
--- a/include/linux/i3c/ccc.h
+++ b/include/linux/i3c/ccc.h
@@ -12,6 +12,8 @@
 #include <linux/i3c/device.h>
 
 /* I3C CCC (Common Command Codes) related definitions */
+#define I3C_CCC_RETRIES	1
+
 #define I3C_CCC_DIRECT			BIT(7)
 
 #define I3C_CCC_ID(id, broadcast)	\
@@ -374,12 +376,15 @@ struct i3c_ccc_cmd_dest {
  * @ndests: number of destinations. Should always be one for broadcast commands
  * @dests: array of destinations and associated payload for this CCC. Most of
  *	   the time, only one destination is provided
+ * @retries: number of times to retry a failed Direct GET CCC (see
+ *	     &I3C_CCC_RETRIES)
  * @err: I3C error code
  */
 struct i3c_ccc_cmd {
 	u8 rnw;
 	u8 id;
 	unsigned int ndests;
+	unsigned int retries;
 	struct i3c_ccc_cmd_dest *dests;
 	enum i3c_error_code err;
 };
-- 
2.43.7