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From:   Romain Izard <romain.izard.pro@gmail.com>
To:     Felipe Balbi <balbi@kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Andrzej Pietrasiewicz <andrzej.p@samsung.com>
Cc:     linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org,
        Romain Izard <romain.izard.pro@gmail.com>
Subject: [PATCH 1/2] usb: gadget: f_ncm: Fix NTP-32 support
Date:   Tue, 16 Apr 2019 16:07:31 +0200
Message-Id: <20190416140732.21941-1-romain.izard.pro@gmail.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

When connecting a CDC-NCM gadget to an host that uses the NTP-32 mode,
or that relies on the default CRC setting, the current implementation gets
confused, and does not expect the correct signature for its packets.

Fix this, by ensuring that the ndp_sign member in the f_ncm structure
always contain a valid value.

Signed-off-by: Romain Izard <romain.izard.pro@gmail.com>
---
 drivers/usb/gadget/function/f_ncm.c | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/drivers/usb/gadget/function/f_ncm.c b/drivers/usb/gadget/function/f_ncm.c
index 5780fba620ab..d5c47e7a7f61 100644
--- a/drivers/usb/gadget/function/f_ncm.c
+++ b/drivers/usb/gadget/function/f_ncm.c
@@ -35,9 +35,7 @@
 
 /* to trigger crc/non-crc ndp signature */
 
-#define NCM_NDP_HDR_CRC_MASK	0x01000000
 #define NCM_NDP_HDR_CRC		0x01000000
-#define NCM_NDP_HDR_NOCRC	0x00000000
 
 enum ncm_notify_state {
 	NCM_NOTIFY_NONE,		/* don't notify */
@@ -526,6 +524,7 @@ static inline void ncm_reset_values(struct f_ncm *ncm)
 {
 	ncm->parser_opts = &ndp16_opts;
 	ncm->is_crc = false;
+	ncm->ndp_sign = ncm->parser_opts->ndp_sign;
 	ncm->port.cdc_filter = DEFAULT_FILTER;
 
 	/* doesn't make sense for ncm, fixed size used */
@@ -805,25 +804,20 @@ static int ncm_setup(struct usb_function *f, const struct usb_ctrlrequest *ctrl)
 	case ((USB_DIR_OUT | USB_TYPE_CLASS | USB_RECIP_INTERFACE) << 8)
 		| USB_CDC_SET_CRC_MODE:
 	{
-		int ndp_hdr_crc = 0;
-
 		if (w_length != 0 || w_index != ncm->ctrl_id)
 			goto invalid;
 		switch (w_value) {
 		case 0x0000:
 			ncm->is_crc = false;
-			ndp_hdr_crc = NCM_NDP_HDR_NOCRC;
 			DBG(cdev, "non-CRC mode selected\n");
 			break;
 		case 0x0001:
 			ncm->is_crc = true;
-			ndp_hdr_crc = NCM_NDP_HDR_CRC;
 			DBG(cdev, "CRC mode selected\n");
 			break;
 		default:
 			goto invalid;
 		}
-		ncm->ndp_sign = ncm->parser_opts->ndp_sign | ndp_hdr_crc;
 		value = 0;
 		break;
 	}
@@ -840,6 +834,8 @@ static int ncm_setup(struct usb_function *f, const struct usb_ctrlrequest *ctrl)
 			ctrl->bRequestType, ctrl->bRequest,
 			w_value, w_index, w_length);
 	}
+	ncm->ndp_sign = ncm->parser_opts->ndp_sign |
+		(ncm->is_crc ? NCM_NDP_HDR_CRC : 0);
 
 	/* respond with data transfer or status phase? */
 	if (value >= 0) {
-- 
2.17.1