linux-kernel - Re: [PATCH] usb: gadget: f_midi: Add checking if it need align buffer's size to an ep's maxpacketsize

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Date:	Fri, 08 Jul 2016 15:04:55 +0200
From:	Michal Nazarewicz <mina86@...a86.com>
To:	Baolin Wang <baolin.wang@...aro.org>
Cc:	Felipe Balbi <balbi@...nel.org>,
	Greg KH <gregkh@...uxfoundation.org>, eu@...ipetonello.com,
	dan.carpenter@...cle.com, USB <linux-usb@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Mark Brown <broonie@...nel.org>
Subject: Re: [PATCH] usb: gadget: f_midi: Add checking if it need align buffer's size to an ep's maxpacketsize

On Fri, Jul 08 2016, Baolin Wang wrote:
> On 7 July 2016 at 20:51, Michal Nazarewicz <mina86@...a86.com> wrote:
>> On Thu, Jul 07 2016, Baolin Wang wrote:
>>> Some gadget device (such as dwc3 gadget) requires quirk_ep_out_aligned_size
>>> attribute, which means it need to align the request buffer's size to an ep's
>>> maxpacketsize.
>>>
>>> Thus we add usb_ep_align_maybe() function to check if it is need to align
>>> the request buffer's size to an ep's maxpacketsize.
>>>
>>> Signed-off-by: Baolin Wang <baolin.wang@...aro.org>
>>
>> Acked-by: Michal Nazarewicz <mina86@...a86.com>
>>
>>> ---
>>>  drivers/usb/gadget/function/f_midi.c |   18 +++++++++++-------
>>>  1 file changed, 11 insertions(+), 7 deletions(-)
>>>
>>> diff --git a/drivers/usb/gadget/function/f_midi.c b/drivers/usb/gadget/function/f_midi.c
>>> index 58fc199..2e3f11e 100644
>>> --- a/drivers/usb/gadget/function/f_midi.c
>>> +++ b/drivers/usb/gadget/function/f_midi.c
>>> @@ -328,7 +328,7 @@ static int f_midi_start_ep(struct f_midi *midi,
>>>  static int f_midi_set_alt(struct usb_function *f, unsigned intf, unsigned alt)
>>>  {
>>>       struct f_midi *midi = func_to_midi(f);
>>> -     unsigned i;
>>> +     unsigned i, length;
>>>       int err;
>>>
>>>       /* we only set alt for MIDIStreaming interface */
>>> @@ -345,9 +345,11 @@ static int f_midi_set_alt(struct usb_function *f, unsigned intf, unsigned alt)
>>>
>>>       /* pre-allocate write usb requests to use on f_midi_transmit. */
>>>       while (kfifo_avail(&midi->in_req_fifo)) {
>>> -             struct usb_request *req =
>>> -                     midi_alloc_ep_req(midi->in_ep, midi->buflen);
>>> +             struct usb_request *req;
>>>
>>> +             length = usb_ep_align_maybe(midi->gadget, midi->in_ep,
>>> +                                         midi->buflen);
>>> +             req = midi_alloc_ep_req(midi->in_ep, length);
>>>               if (req == NULL)
>>>                       return -ENOMEM;
>>>
>>> @@ -359,10 +361,12 @@ static int f_midi_set_alt(struct usb_function *f, unsigned intf, unsigned alt)
>>>
>>>       /* allocate a bunch of read buffers and queue them all at once. */
>>>       for (i = 0; i < midi->qlen && err == 0; i++) {
>>> -             struct usb_request *req =
>>> -                     midi_alloc_ep_req(midi->out_ep,
>>> -                             max_t(unsigned, midi->buflen,
>>> -                                     bulk_out_desc.wMaxPacketSize));
>>> +             struct usb_request *req;
>>> +
>>> +             length = usb_ep_align_maybe(midi->gadget, midi->out_ep,
>>> +                                         midi->buflen);
>>> +             req = midi_alloc_ep_req(midi->out_ep,
>>> +                     max_t(unsigned, length, bulk_out_desc.wMaxPacketSize));
>>
>> Perhaps:
>>
>> +               length = midi->buflen < bulk_out_desc.wMaxPacketSize
>> +                       ? bulk_out_desc.wMaxPacketSize
>> +                       : usb_ep_align_maybe(midi->gadget, midi->out_ep,
>> +                                            midi->buflen);
>> +               req = midi_alloc_ep_req(midi->out_ep, length);
>>
>> I find it somewhat cleaner.  Up to you.
>
> But if the gadget does not requires 'quirk_ep_out_aligned_size', then
> we also can keep midi->buflen length although midi->buflen <
> bulk_out_desc.wMaxPacketSize, right? Thanks for your comment.

I don’t know.  That’s not what the original code was doing.  The
original code was using:

    max_t(unsigned, midi->buflen, bulk_out_desc.wMaxPacketSize));

for some reason.>

>>>               if (req == NULL)
>>>                       return -ENOMEM;
>>>
>>
>> --
>> Best regards
>> ミハウ “𝓶𝓲𝓷𝓪86” ナザレヴイツ
>> «If at first you don’t succeed, give up skydiving»
>
>
>
> -- 
> Baolin.wang
> Best Regards

-- 
Best regards
ミハウ “𝓶𝓲𝓷𝓪86” ナザレヴイツ
«If at first you don’t succeed, give up skydiving»