linux-kernel - Re: [PATCH v3 1/4] usb: gadget: f_midi: free usb request when done

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Date:	Fri, 9 Oct 2015 15:55:51 -0500
From:	Felipe Balbi <balbi@...com>
To:	Clemens Ladisch <clemens@...isch.de>,
	Felipe Tonello <eu@...ipetonello.com>,
	USB list <linux-usb@...r.kernel.org>
CC:	Kernel development list <linux-kernel@...r.kernel.org>,
	Peter Chen <Peter.Chen@...escale.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Andrzej Pietrasiewicz <andrzej.p@...sung.com>
Subject: Re: [PATCH v3 1/4] usb: gadget: f_midi: free usb request when done


Hi,

Clemens Ladisch <clemens@...isch.de> writes:
> Felipe Tonello wrote:
>> req->actual == req->length means that there is no data left to enqueue,
>
> This condition is not checked in the patch.
>
>> so free the request.
>>
>> Signed-off-by: Felipe F. Tonello <eu@...ipetonello.com>
>> ---
>>  drivers/usb/gadget/function/f_midi.c | 5 ++---
>>  1 file changed, 2 insertions(+), 3 deletions(-)
>> diff --git a/drivers/usb/gadget/function/f_midi.c b/drivers/usb/gadget/function/f_midi.c
>> index edb84ca..93212ca 100644
>> --- a/drivers/usb/gadget/function/f_midi.c
>> +++ b/drivers/usb/gadget/function/f_midi.c
>> @@ -256,9 +256,8 @@ f_midi_complete(struct usb_ep *ep, struct usb_request *req)
>>  			/* We received stuff. req is queued again, below */
>>  			f_midi_handle_out_data(ep, req);
>>  		} else if (ep == midi->in_ep) {
>> -			/* Our transmit completed. See if there's more to go.
>> -			 * f_midi_transmit eats req, don't queue it again. */
>> -			f_midi_transmit(midi, req);
>> +			/* Our transmit completed. Don't queue it again. */
>> +			free_ep_req(ep, req);
>>  			return;
>>  		}
>>  		break;
>
> The ALSA framework will give you a notification _once_.  If the
> resulting data is larger than midi->buflen, then you have to continue
> sending packets.  This is exactly what the call to f_midi_transmit()
> does.
>
> (To decrease latency, it might be a good idea to queue multiple requests,
> but you wouldn't want to continue piling up requests if the host isn't
> listening.  sound/usb/midi.c just allocates a fixed number of requests,
> and always reuses them.)

so, should I drop this series from my TODO queue ?

-- 
balbi

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