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

[Sergei Shtylyov <sergei.shtylyov@gmail.com>]

On 18.01.2021 0:36, Jeremy Figgins wrote:

> Certain devices such as Winbond Virtual Com Port,
> which is used in some usb printers, will stop
> responding after the usb_control_msg_send()

    Hm, not usblp_set_protocol()?

> calls in usb_set_interface(). These devices work
> fine without having usb_set_interface() called, so
> this flag prevents that call.
> 
> 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.

    Perhaps the handling of that flag should just be extended to yuor case?

>  Signed-off-by: Jeremy Figgins <kernel@jeremyfiggins.com>
> ---
>   drivers/usb/class/usblp.c | 8 +++++++-
>   1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/class/usblp.c b/drivers/usb/class/usblp.c
> index 134dc2005ce9..6e2d58813d7d 100644
> --- a/drivers/usb/class/usblp.c
> +++ b/drivers/usb/class/usblp.c
[...]
> @@ -1332,7 +1334,11 @@ 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->quirks & USBLP_QUIRK_NO_SET_INTF) {
> +		r = 0;
> +	} else {
> +		r = usb_set_interface(usblp->dev, usblp->ifnum, alts);
> +	}

    The braces above not needed at all.

[...]

MBR, Sergei