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:	Mon, 11 Jul 2016 10:26:25 +0800
From:	Baolin Wang <baolin.wang@...aro.org>
To:	Michal Nazarewicz <mina86@...a86.com>
Cc:	Felipe Balbi <balbi@...nel.org>,
	Greg KH <gregkh@...uxfoundation.org>,
	Felipe Ferreri Tonello <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 8 July 2016 at 21:04, Michal Nazarewicz <mina86@...a86.com> wrote:
> 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));

OK.

>
> 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»



-- 
Baolin.wang
Best Regards