[PATCH v2 4/4] platform/chrome: cros_ec_proto: Convert EC error codes to Linux error codes

[Guenter Roeck <linux@roeck-us.net>]

The EC reports a variety of error codes. Most of those, with the exception
of EC_RES_INVALID_VERSION, are converted to -EPROTO. As result, the actual
error code gets lost. In cros_ec_cmd_xfer_status(), convert all EC errors
to Linux error codes to report a more meaningful error to the caller to aid
debugging.

Cc: Yu-Hsuan Hsu <yuhsuan@chromium.org>
Cc: Prashant Malani <pmalani@chromium.org>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
---
v2: No change

Notes:
    I would welcome feedback on the error code translations.
    Can we do better ?

    -ENOTSUPP is not a recommended error code, and checkpatch complains
    about it. It is used in existing code, so I did not change it, but it
    might be worthwhile exploring if we can find a better error code to
    report "version not supported". Possible candidates might be EPROTOTYPE,
    ENOPROTOOPT, EPROTONOSUPPORT, EPFNOSUPPORT, or EAFNOSUPPORT. I don't
    see a direct match, but NFS reports -EPROTONOSUPPORT for unsupported
    protocol versions.

 drivers/platform/chrome/cros_ec_proto.c | 37 +++++++++++++++++++------
 1 file changed, 29 insertions(+), 8 deletions(-)

diff --git a/drivers/platform/chrome/cros_ec_proto.c b/drivers/platform/chrome/cros_ec_proto.c
index 3e745e0fe092..10aa9e483d35 100644
--- a/drivers/platform/chrome/cros_ec_proto.c
+++ b/drivers/platform/chrome/cros_ec_proto.c
@@ -543,6 +543,29 @@ int cros_ec_cmd_xfer(struct cros_ec_device *ec_dev,
 }
 EXPORT_SYMBOL(cros_ec_cmd_xfer);
 
+static const int cros_ec_error_map[] = {
+	[EC_RES_INVALID_COMMAND] = -EOPNOTSUPP,
+	[EC_RES_ERROR] = -EIO,
+	[EC_RES_INVALID_PARAM] = -EINVAL,
+	[EC_RES_ACCESS_DENIED] = -EACCES,
+	[EC_RES_INVALID_RESPONSE] = -EPROTO,
+	[EC_RES_INVALID_VERSION] = -ENOTSUPP,
+	[EC_RES_INVALID_CHECKSUM] = -EBADMSG,
+	[EC_RES_IN_PROGRESS] = -EINPROGRESS,
+	[EC_RES_UNAVAILABLE] = -ENODATA,
+	[EC_RES_TIMEOUT] = -ETIMEDOUT,
+	[EC_RES_OVERFLOW] = -EOVERFLOW,
+	[EC_RES_INVALID_HEADER] = -EBADR,
+	[EC_RES_REQUEST_TRUNCATED] = -EBADR,
+	[EC_RES_RESPONSE_TOO_BIG] = -EFBIG,
+	[EC_RES_BUS_ERROR] = -EFAULT,
+	[EC_RES_BUSY] = -EBUSY,
+	[EC_RES_INVALID_HEADER_VERSION] = -EBADMSG,
+	[EC_RES_INVALID_HEADER_CRC] = -EBADMSG,
+	[EC_RES_INVALID_DATA_CRC] = -EBADMSG,
+	[EC_RES_DUP_UNAVAILABLE] = -ENODATA,
+};
+
 /**
  * cros_ec_cmd_xfer_status() - Send a command to the ChromeOS EC.
  * @ec_dev: EC device.
@@ -555,8 +578,7 @@ EXPORT_SYMBOL(cros_ec_cmd_xfer);
  *
  * Return:
  * >=0 - The number of bytes transferred
- * -ENOTSUPP - Operation not supported
- * -EPROTO - Protocol error
+ * <0 - Linux error code
  */
 int cros_ec_cmd_xfer_status(struct cros_ec_device *ec_dev,
 			    struct cros_ec_command *msg)
@@ -566,13 +588,12 @@ int cros_ec_cmd_xfer_status(struct cros_ec_device *ec_dev,
 	ret = cros_ec_cmd_xfer(ec_dev, msg);
 	if (ret < 0) {
 		dev_err(ec_dev->dev, "Command xfer error (err:%d)\n", ret);
-	} else if (msg->result == EC_RES_INVALID_VERSION) {
-		dev_dbg(ec_dev->dev, "Command invalid version (err:%d)\n",
-			msg->result);
-		return -ENOTSUPP;
 	} else if (msg->result != EC_RES_SUCCESS) {
-		dev_dbg(ec_dev->dev, "Command result (err: %d)\n", msg->result);
-		return -EPROTO;
+		if (msg->result < ARRAY_SIZE(cros_ec_error_map) && cros_ec_error_map[msg->result])
+			ret = cros_ec_error_map[msg->result];
+		else
+			ret = -EPROTO;
+		dev_dbg(ec_dev->dev, "Command result (err: %d [%d])\n", msg->result, ret);
 	}
 
 	return ret;
-- 
2.17.1