[PATCH] platform/chrome: Re-introduce cros_ec_cmd_xfer and use it for ioctls

[Guenter Roeck]

Commit 413dda8f2c6f ("platform/chrome: cros_ec_chardev: Use
cros_ec_cmd_xfer_status helper") inadvertendly changed the userspace ABI.
Previously, cros_ec ioctls would only report errors if the EC communication
failed, and otherwise return success and the result of the EC
communication. An EC command execution failure was reported in the EC
response field. The above mentioned commit changed this behavior, and the
ioctl itself would fail. This breaks userspace commands trying to analyze
the EC command execution error since the actual EC command response is no
longer reported to userspace.

Fix the problem by re-introducing the cros_ec_cmd_xfer() helper, and use it
to handle ioctl messages.

Fixes: 413dda8f2c6f ("platform/chrome: cros_ec_chardev: Use cros_ec_cmd_xfer_status helper")
Cc: Daisuke Nojiri <dnojiri@xxxxxxxxxxxx>
Cc: Rob Barnes <robbarnes@xxxxxxxxxx>
Cc: Rajat Jain <rajatja@xxxxxxxxxx>
Cc: Brian Norris <briannorris@xxxxxxxxxxxx>
Signed-off-by: Guenter Roeck <linux@xxxxxxxxxxxx>
---
 drivers/platform/chrome/cros_ec_chardev.c   |  2 +-
 drivers/platform/chrome/cros_ec_proto.c     | 47 +++++++++++++++++----
 include/linux/platform_data/cros_ec_proto.h |  3 ++
 3 files changed, 42 insertions(+), 10 deletions(-)

diff --git a/drivers/platform/chrome/cros_ec_chardev.c b/drivers/platform/chrome/cros_ec_chardev.c
index e0bce869c49a..fd33de546aee 100644
--- a/drivers/platform/chrome/cros_ec_chardev.c
+++ b/drivers/platform/chrome/cros_ec_chardev.c
@@ -301,7 +301,7 @@ static long cros_ec_chardev_ioctl_xcmd(struct cros_ec_dev *ec, void __user *arg)
 	}
 
 	s_cmd->command += ec->cmd_offset;
-	ret = cros_ec_cmd_xfer_status(ec->ec_dev, s_cmd);
+	ret = cros_ec_cmd_xfer(ec->ec_dev, s_cmd);
 	/* Only copy data to userland if data was received. */
 	if (ret < 0)
 		goto exit;
diff --git a/drivers/platform/chrome/cros_ec_proto.c b/drivers/platform/chrome/cros_ec_proto.c
index c4caf2e2de82..adf57062991f 100644
--- a/drivers/platform/chrome/cros_ec_proto.c
+++ b/drivers/platform/chrome/cros_ec_proto.c
@@ -560,22 +560,25 @@ int cros_ec_query_all(struct cros_ec_device *ec_dev)
 EXPORT_SYMBOL(cros_ec_query_all);
 
 /**
- * cros_ec_cmd_xfer_status() - Send a command to the ChromeOS EC.
+ * cros_ec_cmd_xfer() - Send a command to the ChromeOS EC.
  * @ec_dev: EC device.
  * @msg: Message to write.
  *
- * Call this to send a command to the ChromeOS EC. This should be used instead of calling the EC's
- * cmd_xfer() callback directly. It returns success status only if both the command was transmitted
- * successfully and the EC replied with success status.
+ * Call this to send a command to the ChromeOS EC. This should be used instead
+ * of calling the EC's cmd_xfer() callback directly. This function does not
+ * convert EC error codes to Linux error codes. Most in-kernel users will want
+ * to use cros_ec_cmd_xfer_status() instead since that function implements
+ * the conversion.
  *
  * Return:
- * >=0 - The number of bytes transferred
- * <0 - Linux error code
+ * >0 - The number of bytes returned from EC (excluding the header).
+ * =0 - Successful communication but EC reported a command execution error.
+ *      The EC error code will be reported in msg->result.
+ * <0 - Linux error code (EC communication error).
  */
-int cros_ec_cmd_xfer_status(struct cros_ec_device *ec_dev,
-			    struct cros_ec_command *msg)
+int cros_ec_cmd_xfer(struct cros_ec_device *ec_dev, struct cros_ec_command *msg)
 {
-	int ret, mapped;
+	int ret;
 
 	mutex_lock(&ec_dev->lock);
 	if (ec_dev->proto_version == EC_PROTO_VERSION_UNKNOWN) {
@@ -616,6 +619,32 @@ int cros_ec_cmd_xfer_status(struct cros_ec_device *ec_dev,
 	ret = send_command(ec_dev, msg);
 	mutex_unlock(&ec_dev->lock);
 
+	return ret;
+}
+EXPORT_SYMBOL(cros_ec_cmd_xfer);
+
+/**
+ * cros_ec_cmd_xfer_status() - Send a command to the ChromeOS EC.
+ * @ec_dev: EC device.
+ * @msg: Message to write.
+ *
+ * Call this to send a command to the ChromeOS EC. This should be used instead of calling the EC's
+ * cmd_xfer() callback directly. It returns success status only if both the command was transmitted
+ * successfully and the EC replied with success status.
+ *
+ * Return:
+ * >=0 - The number of bytes transferred.
+ * <0 - Linux error code
+ */
+int cros_ec_cmd_xfer_status(struct cros_ec_device *ec_dev,
+			    struct cros_ec_command *msg)
+{
+	int ret, mapped;
+
+	ret = cros_ec_cmd_xfer(ec_dev, msg);
+	if (ret < 0)
+		return ret;
+
 	mapped = cros_ec_map_error(msg->result);
 	if (mapped) {
 		dev_dbg(ec_dev->dev, "Command result (err: %d [%d])\n",
diff --git a/include/linux/platform_data/cros_ec_proto.h b/include/linux/platform_data/cros_ec_proto.h
index df3c78c92ca2..16931569adce 100644
--- a/include/linux/platform_data/cros_ec_proto.h
+++ b/include/linux/platform_data/cros_ec_proto.h
@@ -216,6 +216,9 @@ int cros_ec_prepare_tx(struct cros_ec_device *ec_dev,
 int cros_ec_check_result(struct cros_ec_device *ec_dev,
 			 struct cros_ec_command *msg);
 
+int cros_ec_cmd_xfer(struct cros_ec_device *ec_dev,
+		     struct cros_ec_command *msg);
+
 int cros_ec_cmd_xfer_status(struct cros_ec_device *ec_dev,
 			    struct cros_ec_command *msg);
 
-- 
2.35.1