On Wed, 20 Jun 2018 11:38:27 +0200,
Sebastian Andrzej Siewior wrote:
>
> Using usb_fill_int_urb() helps to find code which initializes an
> URB. A grep for members of the struct (like ->complete) reveal lots
> of other things, too.
>
> data_ep_set_params() additionally sets urb->transfer_buffer_length which
> was not the case earlier.
> usb_fill_int_urb() ensures that syncinterval is within the allowed range
> on HS/SS. The interval value seems to come from
> snd_usb_parse_datainterval() which is bInterval - 1 and only in the rage
> 1 … 4. So in order to keep the magic working I pass datainterval + 1.
This needs more explanation. By this conversion, the interval
computation becomes really tricky.
There are two interval calculations. The first one is
fp->datainterval and it's from snd_usb_parse_datainterval() as you
mentioned. And a tricky part is that fp->datainterval is 0 on
FULL_SPEED. Casually, fp->datainterval+1 will be translated to the
correct value since (0 + 1) == (1 << 0).
OTOH, for the sync EP, it's taken from ep->syncinterval, which is set
in snd_usb_add_endpoint(). Luckily, again, ep->syncinterval + 1 works
for FULL_SPEED as well, as (1 + 1) == (1 << 1).
thanks,
Takashi
> Cc: Jaroslav Kysela <perex@xxxxxxxx>
> Cc: Takashi Iwai <tiwai@xxxxxxxx>
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
> ---
> v1…v2: description changes (spelling + usb_fill_int_urb() ensures
> "syncinterval" not data_ep_set_params())
>
> sound/usb/endpoint.c | 24 ++++++++++--------------
> 1 file changed, 10 insertions(+), 14 deletions(-)
>
> diff --git a/sound/usb/endpoint.c b/sound/usb/endpoint.c
> index c90607ebe155..bbc02db5b417 100644
> --- a/sound/usb/endpoint.c
> +++ b/sound/usb/endpoint.c
> @@ -772,6 +772,8 @@ static int data_ep_set_params(struct snd_usb_endpoint *ep,
> /* allocate and initialize data urbs */
> for (i = 0; i < ep->nurbs; i++) {
> struct snd_urb_ctx *u = &ep->urb[i];
> + void *buf;
> +
> u->index = i;
> u->ep = ep;
> u->packets = urb_packs;
> @@ -783,16 +785,13 @@ static int data_ep_set_params(struct snd_usb_endpoint *ep,
> if (!u->urb)
> goto out_of_memory;
>
> - u->urb->transfer_buffer =
> - usb_alloc_coherent(ep->chip->dev, u->buffer_size,
> - GFP_KERNEL, &u->urb->transfer_dma);
> - if (!u->urb->transfer_buffer)
> + buf = usb_alloc_coherent(ep->chip->dev, u->buffer_size,
> + GFP_KERNEL, &u->urb->transfer_dma);
> + if (!buf)
> goto out_of_memory;
> - u->urb->pipe = ep->pipe;
> + usb_fill_int_urb(u->urb, NULL, ep->pipe, buf, u->buffer_size,
> + snd_complete_urb, u, ep->datainterval + 1);
> u->urb->transfer_flags = URB_NO_TRANSFER_DMA_MAP;
> - u->urb->interval = 1 << ep->datainterval;
> - u->urb->context = u;
> - u->urb->complete = snd_complete_urb;
> INIT_LIST_HEAD(&u->ready_list);
> }
>
> @@ -823,15 +822,12 @@ static int sync_ep_set_params(struct snd_usb_endpoint *ep)
> u->urb = usb_alloc_urb(1, GFP_KERNEL);
> if (!u->urb)
> goto out_of_memory;
> - u->urb->transfer_buffer = ep->syncbuf + i * 4;
> + usb_fill_int_urb(u->urb, NULL, ep->pipe, ep->syncbuf + i * 4, 4,
> + snd_complete_urb, u, ep->syncinterval + 1);
> +
> u->urb->transfer_dma = ep->sync_dma + i * 4;
> - u->urb->transfer_buffer_length = 4;
> - u->urb->pipe = ep->pipe;
> u->urb->transfer_flags = URB_NO_TRANSFER_DMA_MAP;
> u->urb->number_of_packets = 1;
> - u->urb->interval = 1 << ep->syncinterval;
> - u->urb->context = u;
> - u->urb->complete = snd_complete_urb;
> }
>
> ep->nurbs = SYNC_URBS;
> --
> 2.17.1
>
>
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