linux-kernel - Re: [PATCH v2] usb: gadget: f_midi: Add checking if it need align buffer's size to an ep's maxpacketsize

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Message-ID: <CAMz4kuK5vdZj-W+EMZCORJ1tccA9OBzmty+T81KmGA4vnW6hrg@mail.gmail.com>
Date:	Tue, 12 Jul 2016 13:14:09 +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>,
	r.baldyga@...sung.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 v2] usb: gadget: f_midi: Add checking if it need align
 buffer's size to an ep's maxpacketsize

On 11 July 2016 at 19:38, Michal Nazarewicz <mina86@...a86.com> wrote:
> On Mon, Jul 11 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>
>> ---
>> Changelog since v1:
>>  - Remove the in_ep modification.
>>  - Remove max_t() function.
>>
>>  drivers/usb/gadget/function/f_midi.c |   12 ++++++++----
>>  1 file changed, 8 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/usb/gadget/function/f_midi.c b/drivers/usb/gadget/function/f_midi.c
>> index 58fc199..59f6278 100644
>> --- a/drivers/usb/gadget/function/f_midi.c
>> +++ b/drivers/usb/gadget/function/f_midi.c
>> @@ -359,10 +359,14 @@ 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;
>> +             unsigned length;
>> +
>> +             length = midi->buflen < bulk_out_desc.wMaxPacketSize
>> +                     ? bulk_out_desc.wMaxPacketSize
>> +                     : usb_ep_align_maybe(midi->gadget, midi->out_ep,
>> +                                          midi->buflen);
>
> As pointed out by Felipe, the packet does not need to be wMaxPacketSize
> so this can simply be:

OK. Thanks.

>
>> +             length = usb_ep_align_maybe(midi->gadget, midi->out_ep,
>> +                                         midi->buflen);
>
>> +             req = midi_alloc_ep_req(midi->out_ep, length);
>>               if (req == NULL)
>>                       return -ENOMEM;
>>
>> --
>> 1.7.9.5
>>
>
> --
> 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