[PATCH v5 3/5] i3c: use actual_len for read transfers

[Sam Agazaryan]

Currently only the amd and svc I3C controller drivers populate
i3c_xfer.actual_len on reads, while dw-i3c-master and mipi-i3c-hci
overwrite i3c_xfer.len with the received byte count and leave actual_len
as 0. Because of this inconsistency, mctp-i3c reads xfer.len instead of
xfer.actual_len, making it fail on controllers that do not mutate len.

Unify read length reporting across the subsystem:
- Clarify in <linux/i3c/device.h> that actual_len reflects the actual
  number of bytes transferred on reads.
- Update adi, cdns, dw, mipi-i3c-hci, and renesas controller drivers to
  populate actual_len on read transfers without mutating len.
- Update mctp-i3c to read xfer.actual_len instead of xfer.len.

Co-developed-by: Meagan Lloyd <meaganlloyd at linux.microsoft.com>
Signed-off-by: Meagan Lloyd <meaganlloyd at linux.microsoft.com>
Signed-off-by: Sam Agazaryan <samagazaryan at google.com>
---
 drivers/i3c/master/adi-i3c-master.c    |  5 ++++-
 drivers/i3c/master/dw-i3c-master.c     |  2 +-
 drivers/i3c/master/i3c-master-cdns.c   |  5 ++++-
 drivers/i3c/master/mipi-i3c-hci/core.c |  2 +-
 drivers/i3c/master/renesas-i3c.c       |  3 +++
 drivers/net/mctp/mctp-i3c.c            | 10 +++++-----
 include/linux/i3c/device.h             |  2 +-
 7 files changed, 19 insertions(+), 10 deletions(-)

diff --git a/drivers/i3c/master/adi-i3c-master.c b/drivers/i3c/master/adi-i3c-master.c
index b35386260350..d033bfd4ecc2 100644
--- a/drivers/i3c/master/adi-i3c-master.c
+++ b/drivers/i3c/master/adi-i3c-master.c
@@ -412,8 +412,11 @@ static int adi_i3c_master_i3c_xfers(struct i3c_dev_desc *dev,
 
 	ret = xfer->ret;
 
-	for (i = 0; i < nxfers; i++)
+	for (i = 0; i < nxfers; i++) {
 		xfers[i].err = adi_i3c_cmd_get_err(&xfer->cmds[i]);
+		if (xfers[i].rnw)
+			xfers[i].actual_len = xfer->cmds[i].rx_len;
+	}
 
 	return ret;
 }
diff --git a/drivers/i3c/master/dw-i3c-master.c b/drivers/i3c/master/dw-i3c-master.c
index 4563d8761ba0..28e8eb293747 100644
--- a/drivers/i3c/master/dw-i3c-master.c
+++ b/drivers/i3c/master/dw-i3c-master.c
@@ -1029,7 +1029,7 @@ static int dw_i3c_master_i3c_xfers(struct i3c_dev_desc *dev,
 		struct dw_i3c_cmd *cmd = &xfer->cmds[i];
 
 		if (i3c_xfers[i].rnw)
-			i3c_xfers[i].len = cmd->rx_len;
+			i3c_xfers[i].actual_len = cmd->rx_len;
 	}
 
 	ret = xfer->ret;
diff --git a/drivers/i3c/master/i3c-master-cdns.c b/drivers/i3c/master/i3c-master-cdns.c
index 2d98c1ce9b12..331062c10b31 100644
--- a/drivers/i3c/master/i3c-master-cdns.c
+++ b/drivers/i3c/master/i3c-master-cdns.c
@@ -795,8 +795,11 @@ static int cdns_i3c_master_i3c_xfers(struct i3c_dev_desc *dev,
 
 	ret = cdns_xfer->ret;
 
-	for (i = 0; i < nxfers; i++)
+	for (i = 0; i < nxfers; i++) {
 		xfers[i].err = cdns_i3c_cmd_get_err(&cdns_xfer->cmds[i]);
+		if (xfers[i].rnw)
+			xfers[i].actual_len = cdns_xfer->cmds[i].rx_len;
+	}
 
 	cdns_i3c_master_free_xfer(cdns_xfer);
 
diff --git a/drivers/i3c/master/mipi-i3c-hci/core.c b/drivers/i3c/master/mipi-i3c-hci/core.c
index dadf049bd4b5..f74c02fab9e3 100644
--- a/drivers/i3c/master/mipi-i3c-hci/core.c
+++ b/drivers/i3c/master/mipi-i3c-hci/core.c
@@ -509,7 +509,7 @@ static int i3c_hci_i3c_xfers(struct i3c_dev_desc *dev,
 		goto out;
 	for (i = 0; i < nxfers; i++) {
 		if (i3c_xfers[i].rnw)
-			i3c_xfers[i].len = RESP_DATA_LENGTH(xfer[i].response);
+			i3c_xfers[i].actual_len = RESP_DATA_LENGTH(xfer[i].response);
 		if (RESP_STATUS(xfer[i].response) != RESP_SUCCESS) {
 			ret = -EIO;
 			goto out;
diff --git a/drivers/i3c/master/renesas-i3c.c b/drivers/i3c/master/renesas-i3c.c
index 28c0927a0179..a3dcb4cd9b0e 100644
--- a/drivers/i3c/master/renesas-i3c.c
+++ b/drivers/i3c/master/renesas-i3c.c
@@ -918,6 +918,9 @@ static int renesas_i3c_i3c_xfers(struct i3c_dev_desc *dev, struct i3c_xfer *i3c_
 		time_left = renesas_i3c_wait_xfer(i3c, xfer);
 		if (!time_left)
 			xfer_failed = true;
+
+		if (i3c_xfers[i].rnw)
+			i3c_xfers[i].actual_len = cmd->rx_count;
 	}
 
 	if (xfer_failed)
diff --git a/drivers/net/mctp/mctp-i3c.c b/drivers/net/mctp/mctp-i3c.c
index 6d2bbae7477b..5f94c11a1712 100644
--- a/drivers/net/mctp/mctp-i3c.c
+++ b/drivers/net/mctp/mctp-i3c.c
@@ -131,12 +131,12 @@ static int mctp_i3c_read(struct mctp_i3c_device *mi)
 	if (rc < 0)
 		goto err;
 
-	if (WARN_ON_ONCE(xfer.len > mi->mrl)) {
+	if (WARN_ON_ONCE(xfer.actual_len > mi->mrl)) {
 		/* Bad i3c bus driver */
 		rc = -EIO;
 		goto err;
 	}
-	if (xfer.len < MCTP_I3C_MINLEN) {
+	if (xfer.actual_len < MCTP_I3C_MINLEN) {
 		stats->rx_length_errors++;
 		rc = -EIO;
 		goto err;
@@ -145,15 +145,15 @@ static int mctp_i3c_read(struct mctp_i3c_device *mi)
 	/* check PEC, including address byte */
 	addr = mi->addr << 1 | 1;
 	pec = i2c_smbus_pec(0, &addr, 1);
-	pec = i2c_smbus_pec(pec, xfer.data.in, xfer.len - 1);
-	if (pec != ((u8 *)xfer.data.in)[xfer.len - 1]) {
+	pec = i2c_smbus_pec(pec, xfer.data.in, xfer.actual_len - 1);
+	if (pec != ((u8 *)xfer.data.in)[xfer.actual_len - 1]) {
 		stats->rx_crc_errors++;
 		rc = -EINVAL;
 		goto err;
 	}
 
 	/* Remove PEC */
-	skb_trim(skb, xfer.len - 1);
+	skb_trim(skb, xfer.actual_len - 1);
 
 	cb = __mctp_cb(skb);
 	cb->halen = PID_SIZE;
diff --git a/include/linux/i3c/device.h b/include/linux/i3c/device.h
index 971d53349b6f..f868a7bf2bc9 100644
--- a/include/linux/i3c/device.h
+++ b/include/linux/i3c/device.h
@@ -59,7 +59,7 @@ enum i3c_xfer_mode {
  * @rnw: encodes the transfer direction. true for a read, false for a write
  * @cmd: Read/Write command in HDR mode, read: 0x80 - 0xff, write: 0x00 - 0x7f
  * @len: transfer length in bytes of the transfer
- * @actual_len: actual length in bytes are transferred by the controller
+ * @actual_len: actual length in bytes transferred by the controller on read
  * @data: input/output buffer
  * @data.in: input buffer. Must point to a DMA-able buffer
  * @data.out: output buffer. Must point to a DMA-able buffer
-- 
2.55.0.1082.g2b9226bbc0-goog