On Wed, Mar 9, 2016 at 11:39 AM, Felipe F. Tonello <e...@felipetonello.com>
wrote:
> 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.
>
> Signed-off-by: Felipe F. Tonello <e...@felipetonello.com>
> ---
> drivers/usb/gadget/function/f_midi.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/usb/gadget/function/f_midi.c
> b/drivers/usb/gadget/function/f_midi.c
> index 8475e3dc82d4..826ba641f29d 100644
> --- a/drivers/usb/gadget/function/f_midi.c
> +++ b/drivers/usb/gadget/function/f_midi.c
> @@ -366,7 +366,9 @@ 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;
>
Won't you get a buffer overrun if midi->buflen is less than wMaxPacketSize?
Regards, Steve
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