linux-kernel - [PATCH v2] usb: gadget: uvc: add bInterval checking for HS mode

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Message-ID: <20210308125338.4824-1-pawell@gli-login.cadence.com>
Date:   Mon, 8 Mar 2021 13:53:38 +0100
From:   Pawel Laszczak <pawell@...ence.com>
To:     <balbi@...nel.org>
CC:     <laurent.pinchart@...asonboard.com>, <gregkh@...uxfoundation.org>,
        <linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <peter.chen@...nel.org>, <kurahul@...ence.com>,
        Pawel Laszczak <pawell@...ence.com>
Subject: [PATCH v2] usb: gadget: uvc: add bInterval checking for HS mode

From: Pawel Laszczak <pawell@...ence.com>

Patch adds extra checking for bInterval passed by configfs.
The 5.6.4 chapter of USB Specification (rev. 2.0) say:
"A high-bandwidth endpoint must specify a period of 1x125 µs
(i.e., a bInterval value of 1)."

The issue was observed during testing UVC class on CV.
I treat this change as improvement because we can control
bInterval by configfs.

Signed-off-by: Pawel Laszczak <pawell@...ence.com>

---
Changlog:
v2:
- removed duplicated assignment

 drivers/usb/gadget/function/f_uvc.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/gadget/function/f_uvc.c b/drivers/usb/gadget/function/f_uvc.c
index 44b4352a2676..ed77a126a74f 100644
--- a/drivers/usb/gadget/function/f_uvc.c
+++ b/drivers/usb/gadget/function/f_uvc.c
@@ -633,7 +633,12 @@ uvc_function_bind(struct usb_configuration *c, struct usb_function *f)
 
 	uvc_hs_streaming_ep.wMaxPacketSize =
 		cpu_to_le16(max_packet_size | ((max_packet_mult - 1) << 11));
-	uvc_hs_streaming_ep.bInterval = opts->streaming_interval;
+
+	/* A high-bandwidth endpoint must specify a bInterval value of 1 */
+	if (max_packet_mult > 1)
+		uvc_hs_streaming_ep.bInterval = 1;
+	else
+		uvc_hs_streaming_ep.bInterval = opts->streaming_interval;
 
 	uvc_ss_streaming_ep.wMaxPacketSize = cpu_to_le16(max_packet_size);
 	uvc_ss_streaming_ep.bInterval = opts->streaming_interval;
-- 
2.25.1