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@jeremyfiggins.com 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@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(-)

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);