[PATCH v2 2/2] mfd: cros_ec: Read EC features during probe to catch transfer error

[Andrei Kuchynski]

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 explicitly calling the newly introduced cros_ec_read_features()
function. If the transfer fails, abort the broken device initialization.
Move the initialization of class_dev before this call to prevent a missing
release() callback warning on the error path.

Signed-off-by: Andrei Kuchynski <akuchynski@xxxxxxxxxxxx>
---
 drivers/mfd/cros_ec_dev.c | 18 +++++++++++-------
 1 file changed, 11 insertions(+), 7 deletions(-)

diff --git a/drivers/mfd/cros_ec_dev.c b/drivers/mfd/cros_ec_dev.c
index 39430dd44e30c..a8c6300248d59 100644
--- a/drivers/mfd/cros_ec_dev.c
+++ b/drivers/mfd/cros_ec_dev.c
@@ -203,6 +203,17 @@ static int ec_device_probe(struct platform_device *pdev)
 	ec->features.flags[1] = -1U; /* Not cached yet */
 	device_initialize(&ec->class_dev);
 
+	/*
+	 * Add the class device
+	 */
+	ec->class_dev.class = &cros_class;
+	ec->class_dev.parent = dev;
+	ec->class_dev.release = cros_ec_class_release;
+
+	retval = cros_ec_read_features(ec);
+	if (retval < 0)
+		goto failed;
+
 	for (i = 0; i < ARRAY_SIZE(cros_mcu_devices); i++) {
 		/*
 		 * Check whether this is actually a dedicated MCU rather
@@ -220,13 +231,6 @@ static int ec_device_probe(struct platform_device *pdev)
 		}
 	}
 
-	/*
-	 * Add the class device
-	 */
-	ec->class_dev.class = &cros_class;
-	ec->class_dev.parent = dev;
-	ec->class_dev.release = cros_ec_class_release;
-
 	retval = dev_set_name(&ec->class_dev, "%s", ec_platform->ec_name);
 	if (retval) {
 		dev_err(dev, "dev_set_name failed => %d\n", retval);
-- 
2.54.0.1032.g2f8565e1d1-goog