On Sun, Jan 17, 2021 at 11:44:16PM -0600, Pete Zaitcev wrote:
> On Sun, 17 Jan 2021 15:36:39 -0600
> Jeremy Figgins <kernel@xxxxxxxxxxxxxxxxx> 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);
Would it be practical simply to skip the usb_set_interface() call
whenever alts is 0? After all, devices use altsetting 0 by default; it
shouldn't be necessary to tell them to do so.
Alan Stern
