[PATCH v1 1/3] usb: typec: ucsi: Limit read size on v1.2

[Abhishek Pandit-Subedi <abhishekpandit@google.com>]

From: Abhishek Pandit-Subedi <abhishekpandit@chromium.org>

Between UCSI 1.2 and UCSI 2.0, the size of the MESSAGE_IN region was
increased from 16 to 256. In order to avoid overflowing reads for older
systems, add a mechanism to use the read UCSI version to truncate read
sizes on UCSI v1.2.

Signed-off-by: Abhishek Pandit-Subedi <abhishekpandit@chromium.org>
---
Tested on 6.6 kernel. Dmesg output from this change:
[  105.058162] ucsi_um_test ucsi_um_test_device.0: Registered UCSI
interface with version 3.0.0


 drivers/usb/typec/ucsi/ucsi.c | 26 ++++++++++++++++++++++++--
 drivers/usb/typec/ucsi/ucsi.h | 11 +++++++++++
 2 files changed, 35 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/typec/ucsi/ucsi.c b/drivers/usb/typec/ucsi/ucsi.c
index 5392ec698959..4edf785d203b 100644
--- a/drivers/usb/typec/ucsi/ucsi.c
+++ b/drivers/usb/typec/ucsi/ucsi.c
@@ -36,6 +36,19 @@
  */
 #define UCSI_SWAP_TIMEOUT_MS	5000
 
+static int ucsi_read_message_in(struct ucsi *ucsi, void *buf,
+					  size_t buf_size)
+{
+	/*
+	 * Below UCSI 2.0, MESSAGE_IN was limited to 16 bytes. Truncate the
+	 * reads here.
+	 */
+	if (ucsi->version <= UCSI_VERSION_1_2)
+		buf_size = min_t(size_t, 16, buf_size);
+
+	return ucsi->ops->read(ucsi, UCSI_MESSAGE_IN, buf, buf_size);
+}
+
 static int ucsi_acknowledge_command(struct ucsi *ucsi)
 {
 	u64 ctrl;
@@ -72,7 +85,7 @@ static int ucsi_read_error(struct ucsi *ucsi)
 	if (ret < 0)
 		return ret;
 
-	ret = ucsi->ops->read(ucsi, UCSI_MESSAGE_IN, &error, sizeof(error));
+	ret = ucsi_read_message_in(ucsi, &error, sizeof(error));
 	if (ret)
 		return ret;
 
@@ -170,7 +183,7 @@ int ucsi_send_command(struct ucsi *ucsi, u64 command,
 	length = ret;
 
 	if (data) {
-		ret = ucsi->ops->read(ucsi, UCSI_MESSAGE_IN, data, size);
+		ret = ucsi_read_message_in(ucsi, data, size);
 		if (ret)
 			goto out;
 	}
@@ -1556,6 +1569,15 @@ int ucsi_register(struct ucsi *ucsi)
 	if (!ucsi->version)
 		return -ENODEV;
 
+	/*
+	 * Version format is JJ.M.N (JJ = Major version, M = Minor version,
+	 * N = sub-minor version).
+	 */
+	dev_info(ucsi->dev, "Registered UCSI interface with version %x.%x.%x",
+		 UCSI_BCD_GET_MAJOR(ucsi->version),
+		 UCSI_BCD_GET_MINOR(ucsi->version),
+		 UCSI_BCD_GET_SUBMINOR(ucsi->version));
+
 	queue_delayed_work(system_long_wq, &ucsi->work, 0);
 
 	ucsi_debugfs_register(ucsi);
diff --git a/drivers/usb/typec/ucsi/ucsi.h b/drivers/usb/typec/ucsi/ucsi.h
index 6478016d5cb8..bec920fa6b8a 100644
--- a/drivers/usb/typec/ucsi/ucsi.h
+++ b/drivers/usb/typec/ucsi/ucsi.h
@@ -23,6 +23,17 @@ struct dentry;
 #define UCSI_CONTROL			8
 #define UCSI_MESSAGE_IN			16
 #define UCSI_MESSAGE_OUT		32
+#define UCSIv2_MESSAGE_OUT		272
+
+/* UCSI versions */
+#define UCSI_VERSION_1_2	0x0120
+#define UCSI_VERSION_2_0	0x0200
+#define UCSI_VERSION_2_1	0x0210
+#define UCSI_VERSION_3_0	0x0300
+
+#define UCSI_BCD_GET_MAJOR(_v_)		(((_v_) >> 8) & 0xFF)
+#define UCSI_BCD_GET_MINOR(_v_)		(((_v_) >> 4) & 0x0F)
+#define UCSI_BCD_GET_SUBMINOR(_v_)	((_v_) & 0x0F)
 
 /* Command Status and Connector Change Indication (CCI) bits */
 #define UCSI_CCI_CONNECTOR(_c_)		(((_c_) & GENMASK(7, 1)) >> 1)
-- 
2.43.0.429.g432eaa2c6b-goog