cros_ec_check_features() does not return an error if the underlying
EC_CMD_GET_FEATURES command fails. Consequently, when the Fingerprint
device fails to respond, the probe function ignores the failure and falls
back to installing it as 'cros_ec' device instead of 'cros_fp'.
This leads to a sysfs duplicate filename collision later when the real
'cros_ec' device attempts to register:

  cros-ec-spi spi5.0: EC failed to respond in time
  cros-ec-dev.19.auto: cannot get EC features: -110
  sysfs : cannot create duplicate filename '/class/chromeos/cros_ec'
        : sysfs_do_create_link_sd+0x94/0xdc
        : ec_device_probe+0x150/0x4f0

Fix this by extracting the feature reading logic into a new helper function
cros_ec_read_features() and calling it during ec_device_probe().
If the transfer fails, abort the broken device initialization.

Signed-off-by: Andrei Kuchynski <akuchynski@chromium.org>
---
 drivers/mfd/cros_ec_dev.c                   |  4 +++
 drivers/platform/chrome/cros_ec_proto.c     | 30 +++++++++++++++------
 include/linux/platform_data/cros_ec_proto.h |  2 ++
 3 files changed, 28 insertions(+), 8 deletions(-)

diff --git a/drivers/mfd/cros_ec_dev.c b/drivers/mfd/cros_ec_dev.c
index 39430dd44e30c..7810b1c871849 100644
--- a/drivers/mfd/cros_ec_dev.c
+++ b/drivers/mfd/cros_ec_dev.c
@@ -203,6 +203,10 @@ static int ec_device_probe(struct platform_device *pdev)
 	ec->features.flags[1] = -1U; /* Not cached yet */
 	device_initialize(&ec->class_dev);
 
+	retval = cros_ec_read_features(ec);
+	if (retval < 0)
+		return retval;
+
 	for (i = 0; i < ARRAY_SIZE(cros_mcu_devices); i++) {
 		/*
 		 * Check whether this is actually a dedicated MCU rather
diff --git a/drivers/platform/chrome/cros_ec_proto.c b/drivers/platform/chrome/cros_ec_proto.c
index 1d8d9168ec1aa..724d1313f6b21 100644
--- a/drivers/platform/chrome/cros_ec_proto.c
+++ b/drivers/platform/chrome/cros_ec_proto.c
@@ -946,6 +946,27 @@ u32 cros_ec_get_host_event(struct cros_ec_device *ec_dev)
 }
 EXPORT_SYMBOL(cros_ec_get_host_event);
 
+/**
+ * cros_ec_read_features() - Read EC features
+ *
+ * @ec: EC device.
+ *
+ * Return: >= 0 on success, negative error number on failure.
+ */
+int cros_ec_read_features(struct cros_ec_dev *ec)
+{
+	int ret = cros_ec_cmd(ec->ec_dev, 0, EC_CMD_GET_FEATURES + ec->cmd_offset,
+			      NULL, 0, &ec->features, sizeof(ec->features));
+
+	if (ret < 0) {
+		dev_warn(ec->dev, "cannot get EC features: %d\n", ret);
+		memset(&ec->features, 0, sizeof(ec->features));
+	}
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(cros_ec_read_features);
+
 /**
  * cros_ec_check_features() - Test for the presence of EC features
  *
@@ -960,17 +981,10 @@ EXPORT_SYMBOL(cros_ec_get_host_event);
 bool cros_ec_check_features(struct cros_ec_dev *ec, int feature)
 {
 	struct ec_response_get_features *features = &ec->features;
-	int ret;
 
 	if (features->flags[0] == -1U && features->flags[1] == -1U) {
 		/* features bitmap not read yet */
-		ret = cros_ec_cmd(ec->ec_dev, 0, EC_CMD_GET_FEATURES + ec->cmd_offset,
-				  NULL, 0, features, sizeof(*features));
-		if (ret < 0) {
-			dev_warn(ec->dev, "cannot get EC features: %d\n", ret);
-			memset(features, 0, sizeof(*features));
-		}
-
+		cros_ec_read_features(ec);
 		dev_dbg(ec->dev, "EC features %08x %08x\n",
 			features->flags[0], features->flags[1]);
 	}
diff --git a/include/linux/platform_data/cros_ec_proto.h b/include/linux/platform_data/cros_ec_proto.h
index 6ed1c4c5ce2ef..a1ccecf5e1f83 100644
--- a/include/linux/platform_data/cros_ec_proto.h
+++ b/include/linux/platform_data/cros_ec_proto.h
@@ -271,6 +271,8 @@ int cros_ec_get_next_event(struct cros_ec_device *ec_dev,
 
 u32 cros_ec_get_host_event(struct cros_ec_device *ec_dev);
 
+int cros_ec_read_features(struct cros_ec_dev *ec);
+
 bool cros_ec_check_features(struct cros_ec_dev *ec, int feature);
 
 int cros_ec_get_sensor_count(struct cros_ec_dev *ec);
-- 
2.54.0.746.g67dd491aae-goog