[PATCH 1/4] mfd: cros_ec: Add cros_ec_cmd_xfer_status helper

[Brian Norris <briannorris@chromium.org>]

From: Tomeu Vizoso <tomeu.vizoso@collabora.com>

So that callers of cros_ec_cmd_xfer don't have to repeat boilerplate
code when checking for errors from the EC side.

Signed-off-by: Tomeu Vizoso <tomeu.vizoso@collabora.com>
Reviewed-by: Benson Leung <bleung@chromium.org>
Signed-off-by: Brian Norris <briannorris@chromium.org>
---
Stolen from:
  https://lkml.org/lkml/2016/4/12/342
  https://patchwork.kernel.org/patch/8810001/

 drivers/platform/chrome/cros_ec_proto.c | 15 +++++++++++++++
 include/linux/mfd/cros_ec.h             | 18 ++++++++++++++++++
 2 files changed, 33 insertions(+)

diff --git a/drivers/platform/chrome/cros_ec_proto.c b/drivers/platform/chrome/cros_ec_proto.c
index 990308ca384f..75eb90d2e4f9 100644
--- a/drivers/platform/chrome/cros_ec_proto.c
+++ b/drivers/platform/chrome/cros_ec_proto.c
@@ -380,3 +380,18 @@ int cros_ec_cmd_xfer(struct cros_ec_device *ec_dev,
 	return ret;
 }
 EXPORT_SYMBOL(cros_ec_cmd_xfer);
+
+int cros_ec_cmd_xfer_status(struct cros_ec_device *ec_dev,
+			    struct cros_ec_command *msg)
+{
+	int ret;
+
+	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_SUCCESS)
+		return -EECRESULT - msg->result;
+
+	return ret;
+}
+EXPORT_SYMBOL(cros_ec_cmd_xfer_status);
diff --git a/include/linux/mfd/cros_ec.h b/include/linux/mfd/cros_ec.h
index a677c2bd485c..b43153f1aca5 100644
--- a/include/linux/mfd/cros_ec.h
+++ b/include/linux/mfd/cros_ec.h
@@ -40,6 +40,9 @@
 #define EC_MAX_REQUEST_OVERHEAD		1
 #define EC_MAX_RESPONSE_OVERHEAD	2
 
+/* ec_command return value for non-success result from EC */
+#define EECRESULT 1000
+
 /*
  * Command interface between EC and AP, for LPC, I2C and SPI interfaces.
  */
@@ -224,6 +227,21 @@ int cros_ec_cmd_xfer(struct cros_ec_device *ec_dev,
 		     struct cros_ec_command *msg);
 
 /**
+ * cros_ec_cmd_xfer_status - Send a command to the ChromeOS EC
+ *
+ * This function is identical to cros_ec_cmd_xfer, except it returns succes
+ * status only if both the command was transmitted successfully and the EC
+ * replied with success status. It's not necessary to check msg->result when
+ * using this function.
+ *
+ * @ec_dev: EC device
+ * @msg: Message to write
+ * @return: Num. of bytes transferred on success, <0 on failure
+ */
+int cros_ec_cmd_xfer_status(struct cros_ec_device *ec_dev,
+			    struct cros_ec_command *msg);
+
+/**
  * cros_ec_remove - Remove a ChromeOS EC
  *
  * Call this to deregister a ChromeOS EC, then clean up any private data.
-- 
2.8.0.rc3.226.g39d4020