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

[Baolin Wang]

On 8 July 2016 at 21:27, Felipe Balbi <balbi@xxxxxxxxxx> wrote:
>
> Hi again,
>
> Felipe Balbi <balbi@xxxxxxxxxx> writes:
>> Michal Nazarewicz <mina86@xxxxxxxxxx> writes:
>>> On Fri, Jul 08 2016, Baolin Wang wrote:
>>>> On 7 July 2016 at 20:51, Michal Nazarewicz <mina86@xxxxxxxxxx> 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@xxxxxxxxxx>
>>>>>
>>>>> Acked-by: Michal Nazarewicz <mina86@xxxxxxxxxx>
>>>>>
>>>>>> ---
>>>>>>  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 donât know.  Thatâs not what the original code was doing.  The
>>> original code was using:
>>>
>>>     max_t(unsigned, midi->buflen, bulk_out_desc.wMaxPacketSize));
>>>
>>> for some reason.>
>>
>> My take on this is that it's calling max_t() to try and align to
>> wMaxPacketSize. We can see from original commit what was the intent:
>>
>> commit 03d27ade4941076b34c823d63d91dc895731a595
>> Author: Felipe F. Tonello <eu@xxxxxxxxxxxxxxxxx>
>> Date:   Wed Mar 9 19:39:30 2016 +0000
>>
>>     usb: gadget: f_midi: Fixed a bug when buflen was smaller than wMaxPacketSize
>>
>>     buflen by default (256) is smaller than wMaxPacketSize (512) in high-speed
>>     devices.
>>
>>     That caused the OUT endpoint to freeze if the host send any data packet of
>>     length greater than 256 bytes.
>>
>>     This is an example dump of what happended on that enpoint:
>>     HOST:   [DATA][Length=260][...]
>>     DEVICE: [NAK]
>>     HOST:   [PING]
>>     DEVICE: [NAK]
>>     HOST:   [PING]
>>     DEVICE: [NAK]
>>     ...
>>     HOST:   [PING]
>>     DEVICE: [NAK]
>>
>>     This patch fixes this problem by setting the minimum usb_request's buffer size
>>     for the OUT endpoint as its wMaxPacketSize.
>>
>>     Acked-by: Michal Nazarewicz <mina86@xxxxxxxxxx>
>>     Signed-off-by: Felipe F. Tonello <eu@xxxxxxxxxxxxxxxxx>
>>     Signed-off-by: Felipe Balbi <felipe.balbi@xxxxxxxxxxxxxxx>
>>
>> diff --git a/drivers/usb/gadget/function/f_midi.c b/drivers/usb/gadget/function/f_midi.c
>> index 56e2dde99b03..9ad51dcab982 100644
>> --- a/drivers/usb/gadget/function/f_midi.c
>> +++ b/drivers/usb/gadget/function/f_midi.c
>> @@ -360,7 +360,9 @@ 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, midi->buflen);
>> +                     midi_alloc_ep_req(midi->out_ep,
>> +                             max_t(unsigned, midi->buflen,
>> +                                     bulk_out_desc.wMaxPacketSize));
>>               if (req == NULL)
>>                       return -ENOMEM;
>>
>> Seems to me usb_ep_align_maybe() would cover this case just as well. But
>> then, Felipe's UDC driver seems to need quirk_ep_out_aligned_size. Felipe?
>
> another way to look at this is that buflen < wMaxPacketSize for bulk
> endpoints is kinda weird, so we might just go ahead and allocate buflen
> aligned to wMaxPacketSize for OUT eps.

OK. So I will accept Michal's suggestion as below:

 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);

-- 
Baolin.wang
Best Regards