[PATCH] usb: misc: cypress_cy7c63: check control transfer status

[Keshav Verma <iganschel@gmail.com>]

read_port() currently ignores errors from vendor_command() and always
returns the cached port value. This can report stale data when the USB
control transfer fails or returns a short response.

Return the underlying error for failed transfers and report -EIO if the
device returns fewer bytes than required.

Fixes: 9189bfc2df0f ("[PATCH] USB: rename Cypress CY7C63xxx driver to proper name and fix up some tiny things")
Signed-off-by: Keshav Verma <iganschel@gmail.com>
---
 drivers/usb/misc/cypress_cy7c63.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/usb/misc/cypress_cy7c63.c b/drivers/usb/misc/cypress_cy7c63.c
index 4a7f955ba85b..8601ee0a1ea3 100644
--- a/drivers/usb/misc/cypress_cy7c63.c
+++ b/drivers/usb/misc/cypress_cy7c63.c
@@ -177,6 +177,10 @@ static ssize_t read_port(struct device *dev, struct device_attribute *attr,
 	result = vendor_command(cyp, CYPRESS_READ_PORT, read_id, 0);
 
 	dev_dbg(&cyp->udev->dev, "Result of vendor_command: %d\n\n", result);
+	if (result < 0)
+		return result;
+	if (result < 2)
+		return -EIO;
 
 	return sprintf(buf, "%d", cyp->port[port_num]);
 }
-- 
2.39.5