[PATCH] USB: usblp: add USBLP_QUIRK_NO_SET_INTF flag

From: Jeremy Figgins <kernel@jeremyfiggins.com>
To: zaitcev@redhat.com, gregkh@linuxfoundation.org,
	linux-usb@vger.kernel.org
Subject: [PATCH] USB: usblp: add USBLP_QUIRK_NO_SET_INTF flag
Date: Sun, 17 Jan 2021 15:36:39 -0600	[thread overview]
Message-ID: <YASt5wgOCkXhH2Dv@watson> (raw)

Certain devices such as Winbond Virtual Com Port,
which is used in some usb printers, will stop
responding after the usb_control_msg_send()
calls in usb_set_interface(). These devices work
fine without having usb_set_interface() called, so
this flag prevents that call.

The naming is designed to mirror the existing
USB_QUIRK_NO_SET_INTF flag, but that flag is
not sufficient to make these devices work.

Signed-off-by: Jeremy Figgins <kernel@jeremyfiggins.com>
---
 drivers/usb/class/usblp.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/class/usblp.c b/drivers/usb/class/usblp.c
index 134dc2005ce9..6e2d58813d7d 100644
--- a/drivers/usb/class/usblp.c
+++ b/drivers/usb/class/usblp.c
@@ -209,6 +209,7 @@ struct quirk_printer_struct {
 #define USBLP_QUIRK_BIDIR	0x1	/* reports bidir but requires unidirectional mode (no INs/reads) */
 #define USBLP_QUIRK_USB_INIT	0x2	/* needs vendor USB init string */
 #define USBLP_QUIRK_BAD_CLASS	0x4	/* descriptor uses vendor-specific Class or SubClass */
+#define USBLP_QUIRK_NO_SET_INTF	0x8	/* device can't handle Set-Interface requests */
 
 static const struct quirk_printer_struct quirk_printers[] = {
 	{ 0x03f0, 0x0004, USBLP_QUIRK_BIDIR }, /* HP DeskJet 895C */
@@ -227,6 +228,7 @@ static const struct quirk_printer_struct quirk_printers[] = {
 	{ 0x0482, 0x0010, USBLP_QUIRK_BIDIR }, /* Kyocera Mita FS 820, by zut <kernel@zut.de> */
 	{ 0x04f9, 0x000d, USBLP_QUIRK_BIDIR }, /* Brother Industries, Ltd HL-1440 Laser Printer */
 	{ 0x04b8, 0x0202, USBLP_QUIRK_BAD_CLASS }, /* Seiko Epson Receipt Printer M129C */
+	{ 0x0416, 0x5011, USBLP_QUIRK_NO_SET_INTF }, /* Winbond Electronics Corp. Virtual Com Port */
 	{ 0, 0 }
 };
 
@@ -1332,7 +1334,11 @@ static int usblp_set_protocol(struct usblp *usblp, int protocol)
 	alts = usblp->protocol[protocol].alt_setting;
 	if (alts < 0)
 		return -EINVAL;
-	r = usb_set_interface(usblp->dev, usblp->ifnum, alts);
+	if (usblp->quirks & USBLP_QUIRK_NO_SET_INTF) {
+		r = 0;
+	} else {
+		r = usb_set_interface(usblp->dev, usblp->ifnum, alts);
+	}
 	if (r < 0) {
 		printk(KERN_ERR "usblp: can't set desired altsetting %d on interface %d\n",
 			alts, usblp->ifnum);
-- 
2.29.0

