linux-kernel - Re: [PATCH v4 1/7] usb: gadget: f_midi: Transmit data only when IN ep is enabled

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Date:	Mon, 26 Oct 2015 23:13:04 +0100
From:	Robert Baldyga <r.baldyga@...kerion.com>
To:	"Felipe F. Tonello" <eu@...ipetonello.com>,
	linux-usb@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, Felipe Balbi <balbi@...com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Andrzej Pietrasiewicz <andrzej.p@...sung.com>,
	Clemens Ladisch <clemens@...isch.de>
Subject: Re: [PATCH v4 1/7] usb: gadget: f_midi: Transmit data only when IN ep
 is enabled

Hi Felipe,

On 10/26/2015 05:55 PM, Felipe F. Tonello wrote:
> This makes sure f_midi doesn't try to enqueue data when the IN endpoint is
> disabled, ie, USB cable is disconnected.
> 
> Signed-off-by: Felipe F. Tonello <eu@...ipetonello.com>
> ---
>  drivers/usb/gadget/function/f_midi.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/gadget/function/f_midi.c b/drivers/usb/gadget/function/f_midi.c
> index edb84ca..e08f365 100644
> --- a/drivers/usb/gadget/function/f_midi.c
> +++ b/drivers/usb/gadget/function/f_midi.c
> @@ -87,6 +87,7 @@ struct f_midi {
>  	int index;
>  	char *id;
>  	unsigned int buflen, qlen;
> +	bool in_ep_enabled;

It's not necessary, you can use ep->enabled flag instead.

>  };
>  
>  static inline struct f_midi *func_to_midi(struct usb_function *f)
> @@ -332,6 +333,7 @@ static int f_midi_set_alt(struct usb_function *f, unsigned intf, unsigned alt)
>  	err = f_midi_start_ep(midi, f, midi->in_ep);
>  	if (err)
>  		return err;
> +	midi->in_ep_enabled = true;
>  
>  	err = f_midi_start_ep(midi, f, midi->out_ep);
>  	if (err)
> @@ -387,6 +389,8 @@ static void f_midi_disable(struct usb_function *f)
>  	 */
>  	usb_ep_disable(midi->in_ep);
>  	usb_ep_disable(midi->out_ep);
> +
> +	midi->in_ep_enabled = false;
>  }
>  
>  static int f_midi_snd_free(struct snd_device *device)
> @@ -543,7 +547,7 @@ static void f_midi_transmit(struct f_midi *midi, struct usb_request *req)
>  		}
>  	}
>  
> -	if (req->length > 0) {
> +	if (req->length > 0 && midi->in_ep_enabled) {

You should rather test it at the beginning of this function. Or, even
better, when tasklet is scheduled, because tasklet is the only way this
function can be called when endpoints are disabled.

>  		int err;
>  
>  		err = usb_ep_queue(ep, req, GFP_ATOMIC);
> @@ -1158,6 +1162,7 @@ static struct usb_function *f_midi_alloc(struct usb_function_instance *fi)
>  	midi->index = opts->index;
>  	midi->buflen = opts->buflen;
>  	midi->qlen = opts->qlen;
> +	midi->in_ep_enabled = false;
>  	++opts->refcnt;
>  	mutex_unlock(&opts->lock);
>  
> 

Best regards,
Robert

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