Re: [PATCH] USB: usblp: add USBLP_QUIRK_NO_SET_INTF flag

[Pete Zaitcev <zaitcev@redhat.com>]

On Sun, 17 Jan 2021 15:36:39 -0600
Jeremy Figgins <kernel@jeremyfiggins.com> wrote:

> 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.
> +	{ 0x0416, 0x5011, USBLP_QUIRK_NO_SET_INTF }, /* Winbond Electronics Corp. Virtual Com Port */

Jeremy, thanks for the patch. It looks mostly fine code-wise (quirk is
out of numerical order), but I have a question: did you consider keying
off usblp->dev->quirks instead?

How about this:

diff --git a/drivers/usb/class/usblp.c b/drivers/usb/class/usblp.c
index 37062130a03c..0c4a98f00797 100644
--- a/drivers/usb/class/usblp.c
+++ b/drivers/usb/class/usblp.c
@@ -1315,7 +1315,11 @@ 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->dev->quirks & USB_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);
diff --git a/drivers/usb/core/quirks.c b/drivers/usb/core/quirks.c
index 1b4eb7046b07..632c60401d53 100644
--- a/drivers/usb/core/quirks.c
+++ b/drivers/usb/core/quirks.c
@@ -205,6 +205,9 @@ static const struct usb_device_id usb_quirk_list[] = {
 	/* HP v222w 16GB Mini USB Drive */
 	{ USB_DEVICE(0x03f0, 0x3f40), .driver_info = USB_QUIRK_DELAY_INIT },
 
+	/* Winbond Electronics Corp. Virtual Com Port */
+	{ USB_DEVICE(0x0416, 0x5011), .driver_info = USB_QUIRK_NO_SET_INTF },
+
 	/* Creative SB Audigy 2 NX */
 	{ USB_DEVICE(0x041e, 0x3020), .driver_info = USB_QUIRK_RESET_RESUME },
 

Please let me know if it works for you.

-- Pete