linux-kernel - Re: [PATCH] usb: gadget: f_acm: don't disable disabled EP

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Message-ID: <20200530171552.GC16333@qmqm.qmqm.pl>
Date:   Sat, 30 May 2020 19:15:52 +0200
From:   Michał Mirosław <mirq-linux@...e.qmqm.pl>
To:     Peter Chen <peter.chen@....com>
Cc:     Felipe Balbi <balbi@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] usb: gadget: f_acm: don't disable disabled EP

On Sat, May 30, 2020 at 01:03:17AM +0000, Peter Chen wrote:
>  
> > > > @@ -425,9 +425,11 @@ static int acm_set_alt(struct usb_function *f, unsigned
> > intf, unsigned alt)
> > > >  	/* we know alt == 0, so this is an activation or a reset */
> > > >
> > > >  	if (intf == acm->ctrl_id) {
> > > > -		dev_vdbg(&cdev->gadget->dev,
> > > > -				"reset acm control interface %d\n", intf);
> > > > -		usb_ep_disable(acm->notify);
> > > > +		if (acm->notify->enabled) {
> > > > +			dev_vdbg(&cdev->gadget->dev,
> > > > +					"reset acm control interface %d\n", intf);
> > > > +			usb_ep_disable(acm->notify);
> > > > +		}
> > >
> > > But it does not fix any issues, the usb_ep_disable checks 'enabled' flag.
> > 
> > It generates spurious trace events if you enable them.
> You mean the trace events from core.c? If it is, we could try to improve it
> and indicate it is already enabled or disabled.

It is indicated in return code, but the problem is that this generates
noise and wastes debugging time. The problem I was seeing manifested
itself as disabling disabled EPs and desync of EP state between core
and UDC driver. The patch avoids the noise and makes the code obvious.
(This check was there at some point in time, BTW.)

Best Regards,
Michał Mirosław