[PATCH 5.10 007/120] USB: usblp: dont call usb_set_interface if theres a single alt

Greg Kroah-Hartman
2021-02-08T16:57:57Z

From: Jeremy Figgins <kernel@jeremyfiggins.com>

commit d8c6edfa3f4ee0d45d7ce5ef18d1245b78774b9d upstream.

Some devices, such as the Winbond Electronics Corp. Virtual Com Port
(Vendor=0416, ProdId=5011), lockup when usb_set_interface() or
usb_clear_halt() are called. This device has only a single
altsetting, so it should not be necessary to call usb_set_interface().

Acked-by: Pete Zaitcev <zaitcev@redhat.com>
Signed-off-by: Jeremy Figgins <kernel@jeremyfiggins.com>
Link: https://lore.kernel.org/r/YAy9kJhM/rG8EQXC@watson
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/usb/class/usblp.c | 19 +++++++++++--------
1 file changed, 11 insertions(+), 8 deletions(-)

--- a/drivers/usb/class/usblp.c
+++ b/drivers/usb/class/usblp.c
@@ -1329,14 +1329,17 @@ static int usblp_set_protocol(struct usb
if (protocol < USBLP_FIRST_PROTOCOL || protocol > USBLP_LAST_PROTOCOL)
return -EINVAL;

- alts = usblp->protocol[protocol].alt_setting;
- if (alts < 0)
- return -EINVAL;
- 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);
- return r;
+ /* Don't unnecessarily set the interface if there's a single alt. */
+ if (usblp->intf->num_altsetting > 1) {
+ alts = usblp->protocol[protocol].alt_setting;
+ if (alts < 0)
+ return -EINVAL;
+ 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);
+ return r;
+ }
}

usblp->bidir = (usblp->protocol[protocol].epread != NULL);