[PATCH v2 08/33] HID: logitech-hidpp: do not retry timeouts and transport errors in hidpp_send_message_sync()

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

When a transport failure or timeout occurs, the synchronous send helper
clears the response buffer, setting its report ID to zero. Because the
retry loop only inspects valid HID++ short, long, and very long report
IDs to decide whether to return, a cleared buffer misses both checks and
falls through to the busy-retry path. Every transport error and timeout
is therefore misidentified as a busy error and retried three times while
holding the send mutex.

Return immediately when the low-level helper reports success or a
negative error code, and only retry when the device responds with an
explicit busy protocol error.

Fixes: aba7963544d4 ("HID: logitech-hidpp: Do not assume FAP in hidpp_send_message_sync()")
Cc: stable@vger.kernel.org
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
---
 drivers/hid/hid-logitech-hidpp.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/hid/hid-logitech-hidpp.c b/drivers/hid/hid-logitech-hidpp.c
index 0264e4541edf..c486488efe99 100644
--- a/drivers/hid/hid-logitech-hidpp.c
+++ b/drivers/hid/hid-logitech-hidpp.c
@@ -364,6 +364,9 @@ static int hidpp_send_message_sync(struct hidpp_device *hidpp,
 
 	do {
 		ret = __do_hidpp_send_message_sync(hidpp, message, response);
+		if (ret <= 0)
+			break;
+
 		if (response->report_id == REPORT_ID_HIDPP_SHORT &&
 		    ret != HIDPP_ERROR_BUSY)
 			break;

-- 
2.56.0.542.g3ef89b7020-goog