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

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Date:   Thu, 4 Mar 2021 11:45:15 +0100
From:   Pawel Laszczak <pawell@...ence.com>
To:     <balbi@...nel.org>, <gregkh@...uxfoundation.org>,
        <linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>
CC:     <laurent.pinchart@...asonboard.com>,
        Pawel Laszczak <pawell@...ence.com>
Subject: [PATCH] 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>
---
 drivers/usb/gadget/function/f_uvc.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/usb/gadget/function/f_uvc.c b/drivers/usb/gadget/function/f_uvc.c
index 44b4352a2676..5d62720bb9e1 100644
--- a/drivers/usb/gadget/function/f_uvc.c
+++ b/drivers/usb/gadget/function/f_uvc.c
@@ -631,6 +631,12 @@ uvc_function_bind(struct usb_configuration *c, struct usb_function *f)
 		cpu_to_le16(min(opts->streaming_maxpacket, 1023U));
 	uvc_fs_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_hs_streaming_ep.wMaxPacketSize =
 		cpu_to_le16(max_packet_size | ((max_packet_mult - 1) << 11));
 	uvc_hs_streaming_ep.bInterval = opts->streaming_interval;
-- 
2.25.1