[PATCH v2 11/33] HID: logitech-hidpp: handle negative errors in hidpp20_get_adc_measurement_1f20()

[Dmitry Torokhov <dmitry.torokhov@gmail.com>]

When hidpp_send_fap_command_sync() fails with a negative transport or
timeout error (-ETIMEDOUT, -ENODEV, etc.),
hidpp20_get_adc_measurement_1f20() only checked if (ret > 0) for
protocol errors and fell through. It then parsed zeroed response
parameters (0 mV) and returned true, marking a disconnected or
unresponsive device online and triggering spurious "possibly using the
wrong voltage curve" warnings.

Return false whenever ret is non-zero, logging the debug message only
when ret is a positive protocol error.

Fixes: c361982a13c9 ("HID: logitech-hidpp: Add support for ADC measurement feature")
Cc: stable@vger.kernel.org
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
---
 drivers/hid/hid-logitech-hidpp.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/hid/hid-logitech-hidpp.c b/drivers/hid/hid-logitech-hidpp.c
index 0ec2f2fd6dec..28402baf04fb 100644
--- a/drivers/hid/hid-logitech-hidpp.c
+++ b/drivers/hid/hid-logitech-hidpp.c
@@ -1952,9 +1952,10 @@ static bool hidpp20_get_adc_measurement_1f20(struct hidpp_device *hidpp,
 					  CMD_ADC_MEASUREMENT_GET_ADC_MEASUREMENT,
 					  NULL, 0, &response);
 
-	if (ret > 0) {
-		hid_dbg(hidpp->hid_dev, "%s: received protocol error 0x%02x\n",
-			__func__, ret);
+	if (ret) {
+		if (ret > 0)
+			hid_dbg(hidpp->hid_dev, "%s: received protocol error 0x%02x\n",
+				__func__, ret);
 		return false;
 	}
 

-- 
2.56.0.542.g3ef89b7020-goog