linux-kernel - [PATCH 2/3] usb: raw-gadget: return USB_GADGET_DELAYED

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Date:   Mon, 28 Aug 2023 04:10:31 +0200
From:   andrey.konovalov@...ux.dev
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Alan Stern <stern@...land.harvard.edu>
Cc:     Andrey Konovalov <andreyknvl@...il.com>,
        Felipe Balbi <balbi@...nel.org>,
        Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
        Pawel Laszczak <pawell@...ence.com>,
        Chunfeng Yun <chunfeng.yun@...iatek.com>,
        Minas Harutyunyan <hminas@...opsys.com>,
        Justin Chen <justin.chen@...adcom.com>,
        Al Cooper <alcooperx@...il.com>,
        Herve Codina <herve.codina@...tlin.com>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 2/3] usb: raw-gadget: return USB_GADGET_DELAYED_STATUS from setup()

From: Andrey Konovalov <andreyknvl@...il.com>

Return USB_GADGET_DELAYED_STATUS from the setup() callback for 0-length
transfers as a workaround to stop some UDC drivers (e.g. dwc3) from
automatically proceeding with the status stage.

This workaround should be removed once all UDC drivers are fixed to
always delay the status stage until a response is queued to EP0.

Signed-off-by: Andrey Konovalov <andreyknvl@...il.com>
---
 drivers/usb/gadget/legacy/raw_gadget.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/drivers/usb/gadget/legacy/raw_gadget.c b/drivers/usb/gadget/legacy/raw_gadget.c
index e549022642e5..b9ecc55a2ce2 100644
--- a/drivers/usb/gadget/legacy/raw_gadget.c
+++ b/drivers/usb/gadget/legacy/raw_gadget.c
@@ -25,6 +25,7 @@
 #include <linux/usb/ch9.h>
 #include <linux/usb/ch11.h>
 #include <linux/usb/gadget.h>
+#include <linux/usb/composite.h>
 
 #include <uapi/linux/usb/raw_gadget.h>
 
@@ -363,6 +364,16 @@ static int gadget_setup(struct usb_gadget *gadget,
 out_unlock:
 	spin_unlock_irqrestore(&dev->lock, flags);
 out:
+	if (ret == 0 && ctrl->wLength == 0) {
+		/*
+		 * Return USB_GADGET_DELAYED_STATUS as a workaround to stop
+		 * some UDC drivers (e.g. dwc3) from automatically proceeding
+		 * with the status stage for 0-length transfers.
+		 * Should be removed once all UDC drivers are fixed to always
+		 * delay the status stage until a response is queued to EP0.
+		 */
+		return USB_GADGET_DELAYED_STATUS;
+	}
 	return ret;
 }
 
-- 
2.25.1