[PATCH 3/3] usb: dwc3: gadget: Simplify logic in dwc3_needs_extra_trb()

Johannes Schneider
2025-06-21T19:07:31Z

The existing logic in dwc3_needs_extra_trb() checks multiple conditions
in a compound expression to determine whether an extra TRB is needed,
either for a ZLP or to handle short OUT transfers.

This commit simplifies the logic without changing behavior:
- Returns false early for isochronous endpoints
- Separates the conditions for IN vs OUT transfers
- Makes intent and flow easier to read and reason about

No functional changes intended.

Signed-off-by: Johannes Schneider <johannes.schneider@leica-geosystems.com>
---
drivers/usb/dwc3/gadget.c | 11 ++++++-----
1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index a4a2bf273f943fa112f49979297023a732e0af2e..32d0fb090f4c2ffab61ae6eee29a02efd32ed032 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -1420,12 +1420,13 @@ static bool dwc3_needs_extra_trb(struct dwc3_ep *dep, struct dwc3_request *req)
unsigned int maxp = usb_endpoint_maxp(dep->endpoint.desc);
unsigned int rem = req->request.length % maxp;

- if ((req->request.length && req->request.zero && !rem &&
- !usb_endpoint_xfer_isoc(dep->endpoint.desc)) ||
- (!req->direction && rem))
- return true;
+ if (usb_endpoint_xfer_isoc(dep->endpoint.desc))
+ return false;
+
+ if (!req->direction) /* OUT transfers */
+ return rem != 0;

- return false;
+ return rem == 0;
}

/**

--
2.34.1