This is a note to let you know that I've just added the patch titled
USB: usblp: don't call usb_set_interface if there's a single alt
to my usb git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git
in the usb-linus branch.
The patch will show up in the next release of the linux-next tree
(usually sometime within the next 24 hours during the week.)
The patch will hopefully also be merged in Linus's tree for the
next -rc kernel release.
If you have any questions about this process, please let me know.
>From d8c6edfa3f4ee0d45d7ce5ef18d1245b78774b9d Mon Sep 17 00:00:00 2001
From: Jeremy Figgins <kernel@xxxxxxxxxxxxxxxxx>
Date: Sat, 23 Jan 2021 18:21:36 -0600
Subject: USB: usblp: don't call usb_set_interface if there's a single alt
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@xxxxxxxxxx>
Signed-off-by: Jeremy Figgins <kernel@xxxxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/YAy9kJhM/rG8EQXC@watson
Cc: stable <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/usb/class/usblp.c | 19 +++++++++++--------
1 file changed, 11 insertions(+), 8 deletions(-)
diff --git a/drivers/usb/class/usblp.c b/drivers/usb/class/usblp.c
index 134dc2005ce9..c9f6e9758288 100644
--- a/drivers/usb/class/usblp.c
+++ b/drivers/usb/class/usblp.c
@@ -1329,14 +1329,17 @@ static int usblp_set_protocol(struct usblp *usblp, int protocol)
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);
--
2.30.0
