sound/usb/usx2y/usb_stream.c - kernel/msm-4.19 - Gitiles

 /*
  * Copyright (C) 2007, 2008 Karsten Wiese <fzu@wemgehoertderstaat.de>
  *
  * This program is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License as published by the
  * Free Software Foundation; either version 2 of the License, or (at your
  * option) any later version.
  *
  * This program is distributed in the hope that it will be useful, but
  * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
  * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  * for more details.
  *
  * You should have received a copy of the GNU General Public License
  * along with this program; if not, write to the Free Software Foundation,
  * Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  */

 #include <linux/usb.h>

 #include "usb_stream.h"


 /*                             setup                                  */

 static unsigned usb_stream_next_packet_size(struct usb_stream_kernel *sk)
 {
 	struct usb_stream *s = sk->s;
 	sk->out_phase_peeked = (sk->out_phase & 0xffff) + sk->freqn;
 	return (sk->out_phase_peeked >> 16) * s->cfg.frame_size;
 }

 static void playback_prep_freqn(struct usb_stream_kernel *sk, struct urb *urb)
 {
 	struct usb_stream *s = sk->s;
 	unsigned l = 0;
 	int pack;

 	urb->iso_frame_desc[0].offset = 0;
 	urb->iso_frame_desc[0].length =	usb_stream_next_packet_size(sk);
 	sk->out_phase = sk->out_phase_peeked;
 	urb->transfer_buffer_length = urb->iso_frame_desc[0].length;

 	for (pack = 1; pack < sk->n_o_ps; pack++) {
 		l = usb_stream_next_packet_size(sk);
 		if (s->idle_outsize + urb->transfer_buffer_length + l >
 		    s->period_size)
 			goto check;

 		sk->out_phase = sk->out_phase_peeked;
 		urb->iso_frame_desc[pack].offset = urb->transfer_buffer_length;
 		urb->iso_frame_desc[pack].length = l;
 		urb->transfer_buffer_length += l;
 	}
 	snd_printdd(KERN_DEBUG "%i\n", urb->transfer_buffer_length);

 check:
 	urb->number_of_packets = pack;
 	s->idle_outsize += urb->transfer_buffer_length - s->period_size;
 	snd_printdd(KERN_DEBUG "idle=%i ul=%i ps=%i\n", s->idle_outsize,
 		    urb->transfer_buffer_length, s->period_size);
 }

 static void init_pipe_urbs(struct usb_stream_kernel *sk, unsigned use_packsize,
 			   struct urb **urbs, char *transfer,
 			   struct usb_device *dev, int pipe)
 {
 	int u, p;
 	int maxpacket = use_packsize ?
 		use_packsize : usb_maxpacket(dev, pipe, usb_pipeout(pipe));
 	int transfer_length = maxpacket * sk->n_o_ps;

 	for (u = 0; u < USB_STREAM_NURBS;
 	     ++u, transfer += transfer_length) {
 		struct urb *urb = urbs[u];
 		struct usb_iso_packet_descriptor *desc;
 		urb->transfer_flags = URB_ISO_ASAP;
 		urb->transfer_buffer = transfer;
 		urb->dev = dev;
 		urb->pipe = pipe;
 		urb->number_of_packets = sk->n_o_ps;
 		urb->context = sk;
 		urb->interval = 1;
 		if (usb_pipeout(pipe))
 			continue;

 		urb->transfer_buffer_length = transfer_length;
 		desc = urb->iso_frame_desc;
 		desc->offset = 0;
 		desc->length = maxpacket;
 		for (p = 1; p < sk->n_o_ps; ++p) {
 			desc[p].offset = desc[p - 1].offset + maxpacket;
 			desc[p].length = maxpacket;
 		}
 	}
 }

 static void init_urbs(struct usb_stream_kernel *sk, unsigned use_packsize,
 		      struct usb_device *dev, int in_pipe, int out_pipe)
 {
 	struct usb_stream	*s = sk->s;
 	char			*indata = (char *)s + sizeof(*s) +
 					sizeof(struct usb_stream_packet) *
 					s->inpackets;
 	int			u;

 	for (u = 0; u < USB_STREAM_NURBS; ++u) {
 		sk->inurb[u] = usb_alloc_urb(sk->n_o_ps, GFP_KERNEL);
 		sk->outurb[u] = usb_alloc_urb(sk->n_o_ps, GFP_KERNEL);
 	}

 	init_pipe_urbs(sk, use_packsize, sk->inurb, indata, dev, in_pipe);
 	init_pipe_urbs(sk, use_packsize, sk->outurb, sk->write_page, dev,
 		       out_pipe);
 }


 /*
  * convert a sampling rate into our full speed format (fs/1000 in Q16.16)
  * this will overflow at approx 524 kHz
  */
 static inline unsigned get_usb_full_speed_rate(unsigned rate)
 {
 	return ((rate << 13) + 62) / 125;
 }

 /*
  * convert a sampling rate into USB high speed format (fs/8000 in Q16.16)
  * this will overflow at approx 4 MHz
  */
 static inline unsigned get_usb_high_speed_rate(unsigned rate)
 {
 	return ((rate << 10) + 62) / 125;
 }

 void usb_stream_free(struct usb_stream_kernel *sk)
 {
 	struct usb_stream *s;
 	unsigned u;

 	for (u = 0; u < USB_STREAM_NURBS; ++u) {
 		usb_free_urb(sk->inurb[u]);
 		sk->inurb[u] = NULL;
 		usb_free_urb(sk->outurb[u]);
 		sk->outurb[u] = NULL;
 	}

 	s = sk->s;
 	if (!s)
 		return;

 	free_pages((unsigned long)sk->write_page, get_order(s->write_size));
 	sk->write_page = NULL;
 	free_pages((unsigned long)s, get_order(s->read_size));
 	sk->s = NULL;
 }

 struct usb_stream *usb_stream_new(struct usb_stream_kernel *sk,
 				  struct usb_device *dev,
 				  unsigned in_endpoint, unsigned out_endpoint,
 				  unsigned sample_rate, unsigned use_packsize,
 				  unsigned period_frames, unsigned frame_size)
 {
 	int packets, max_packsize;
 	int in_pipe, out_pipe;
 	int read_size = sizeof(struct usb_stream);
 	int write_size;
 	int usb_frames = dev->speed == USB_SPEED_HIGH ? 8000 : 1000;
 	int pg;

 	in_pipe = usb_rcvisocpipe(dev, in_endpoint);
 	out_pipe = usb_sndisocpipe(dev, out_endpoint);

 	max_packsize = use_packsize ?
 		use_packsize : usb_maxpacket(dev, in_pipe, 0);

 	/*
 		t_period = period_frames / sample_rate
 		iso_packs = t_period / t_iso_frame
 			= (period_frames / sample_rate) * (1 / t_iso_frame)
 	*/

 	packets = period_frames * usb_frames / sample_rate + 1;

 	if (dev->speed == USB_SPEED_HIGH)
 		packets = (packets + 7) & ~7;

 	read_size += packets * USB_STREAM_URBDEPTH *
 		(max_packsize + sizeof(struct usb_stream_packet));

 	max_packsize = usb_maxpacket(dev, out_pipe, 1);
 	write_size = max_packsize * packets * USB_STREAM_URBDEPTH;

 	if (read_size >= 256*PAGE_SIZE || write_size >= 256*PAGE_SIZE) {
 		snd_printk(KERN_WARNING "a size exceeds 128*PAGE_SIZE\n");
 		goto out;
 	}

 	pg = get_order(read_size);
 	sk->s = (void *) __get_free_pages(GFP_KERNEL|__GFP_COMP|__GFP_ZERO, pg);
 	if (!sk->s) {
 		snd_printk(KERN_WARNING "couldn't __get_free_pages()\n");
 		goto out;
 	}
 	sk->s->cfg.version = USB_STREAM_INTERFACE_VERSION;

 	sk->s->read_size = read_size;

 	sk->s->cfg.sample_rate = sample_rate;
 	sk->s->cfg.frame_size = frame_size;
 	sk->n_o_ps = packets;
 	sk->s->inpackets = packets * USB_STREAM_URBDEPTH;
 	sk->s->cfg.period_frames = period_frames;
 	sk->s->period_size = frame_size * period_frames;

 	sk->s->write_size = write_size;
 	pg = get_order(write_size);

 	sk->write_page =
 		(void *)__get_free_pages(GFP_KERNEL|__GFP_COMP|__GFP_ZERO, pg);
 	if (!sk->write_page) {
 		snd_printk(KERN_WARNING "couldn't __get_free_pages()\n");
 		usb_stream_free(sk);
 		return NULL;
 	}

 	/* calculate the frequency in 16.16 format */
 	if (dev->speed == USB_SPEED_FULL)
 		sk->freqn = get_usb_full_speed_rate(sample_rate);
 	else
 		sk->freqn = get_usb_high_speed_rate(sample_rate);

 	init_urbs(sk, use_packsize, dev, in_pipe, out_pipe);
 	sk->s->state = usb_stream_stopped;
 out:
 	return sk->s;
 }


 /*                             start                                  */

 static bool balance_check(struct usb_stream_kernel *sk, struct urb *urb)
 {
 	bool r;
 	if (unlikely(urb->status)) {
 		if (urb->status != -ESHUTDOWN && urb->status != -ENOENT)
 			snd_printk(KERN_WARNING "status=%i\n", urb->status);
 		sk->iso_frame_balance = 0x7FFFFFFF;
 		return false;
 	}
 	r = sk->iso_frame_balance == 0;
 	if (!r)
 		sk->i_urb = urb;
 	return r;
 }

 static bool balance_playback(struct usb_stream_kernel *sk, struct urb *urb)
 {
 	sk->iso_frame_balance += urb->number_of_packets;
 	return balance_check(sk, urb);
 }

 static bool balance_capture(struct usb_stream_kernel *sk, struct urb *urb)
 {
 	sk->iso_frame_balance -= urb->number_of_packets;
 	return balance_check(sk, urb);
 }

 static void subs_set_complete(struct urb **urbs, void (*complete)(struct urb *))
 {
 	int u;

 	for (u = 0; u < USB_STREAM_NURBS; u++) {
 		struct urb *urb = urbs[u];
 		urb->complete = complete;
 	}
 }

 static int usb_stream_prepare_playback(struct usb_stream_kernel *sk,
 		struct urb *inurb)
 {
 	struct usb_stream *s = sk->s;
 	struct urb *io;
 	struct usb_iso_packet_descriptor *id, *od;
 	int p, l = 0;

 	io = sk->idle_outurb;
 	od = io->iso_frame_desc;
 	io->transfer_buffer_length = 0;

 	for (p = 0; s->sync_packet < 0; ++p, ++s->sync_packet) {
 		struct urb *ii = sk->completed_inurb;
 		id = ii->iso_frame_desc +
 			ii->number_of_packets + s->sync_packet;
 		l = id->actual_length;

 		od[p].length = l;
 		od[p].offset = io->transfer_buffer_length;
 		io->transfer_buffer_length += l;
 	}

 	for (;
 	     s->sync_packet < inurb->number_of_packets && p < sk->n_o_ps;
 	     ++p, ++s->sync_packet) {
 		l = inurb->iso_frame_desc[s->sync_packet].actual_length;

 		if (s->idle_outsize + io->transfer_buffer_length + l >
 		    s->period_size)
 			goto check_ok;

 		od[p].length = l;
 		od[p].offset = io->transfer_buffer_length;
 		io->transfer_buffer_length += l;
 	}

 check_ok:
 	s->sync_packet -= inurb->number_of_packets;
 	if (s->sync_packet < -2 || s->sync_packet > 0) {
 		snd_printk(KERN_WARNING "invalid sync_packet = %i;"
 			   " p=%i nop=%i %i %x %x %x > %x\n",
 			   s->sync_packet, p, inurb->number_of_packets,
 			   s->idle_outsize + io->transfer_buffer_length + l,
 			   s->idle_outsize, io->transfer_buffer_length,  l,
 			   s->period_size);
 		return -1;
 	}
 	if (io->transfer_buffer_length % s->cfg.frame_size) {
 		snd_printk(KERN_WARNING"invalid outsize = %i\n",
 			   io->transfer_buffer_length);
 		return -1;
 	}
 	s->idle_outsize += io->transfer_buffer_length - s->period_size;
 	io->number_of_packets = p;
 	if (s->idle_outsize > 0) {
 		snd_printk(KERN_WARNING "idle=%i\n", s->idle_outsize);
 		return -1;
 	}
 	return 0;
 }

 static void prepare_inurb(int number_of_packets, struct urb *iu)
 {
 	struct usb_iso_packet_descriptor *id;
 	int p;

 	iu->number_of_packets = number_of_packets;
 	id = iu->iso_frame_desc;
 	id->offset = 0;
 	for (p = 0; p < iu->number_of_packets - 1; ++p)
 		id[p + 1].offset = id[p].offset + id[p].length;

 	iu->transfer_buffer_length =
 		id[0].length * iu->number_of_packets;
 }

 static int submit_urbs(struct usb_stream_kernel *sk,
 		       struct urb *inurb, struct urb *outurb)
 {
 	int err;
 	prepare_inurb(sk->idle_outurb->number_of_packets, sk->idle_inurb);
 	err = usb_submit_urb(sk->idle_inurb, GFP_ATOMIC);
 	if (err < 0) {
 		snd_printk(KERN_ERR "%i\n", err);
 		return err;
 	}
 	sk->idle_inurb = sk->completed_inurb;
 	sk->completed_inurb = inurb;
 	err = usb_submit_urb(sk->idle_outurb, GFP_ATOMIC);
 	if (err < 0) {
 		snd_printk(KERN_ERR "%i\n", err);
 		return err;
 	}
 	sk->idle_outurb = sk->completed_outurb;
 	sk->completed_outurb = outurb;
 	return 0;
 }

 #ifdef DEBUG_LOOP_BACK
 /*
   This loop_back() shows how to read/write the period data.
  */
 static void loop_back(struct usb_stream *s)
 {
 	char *i, *o;
 	int il, ol, l, p;
 	struct urb *iu;
 	struct usb_iso_packet_descriptor *id;

 	o = s->playback1st_to;
 	ol = s->playback1st_size;
 	l = 0;

 	if (s->insplit_pack >= 0) {
 		iu = sk->idle_inurb;
 		id = iu->iso_frame_desc;
 		p = s->insplit_pack;
 	} else
 		goto second;
 loop:
 	for (; p < iu->number_of_packets && l < s->period_size; ++p) {
 		i = iu->transfer_buffer + id[p].offset;
 		il = id[p].actual_length;
 		if (l + il > s->period_size)
 			il = s->period_size - l;
 		if (il <= ol) {
 			memcpy(o, i, il);
 			o += il;
 			ol -= il;
 		} else {
 			memcpy(o, i, ol);
 			singen_6pack(o, ol);
 			o = s->playback_to;
 			memcpy(o, i + ol, il - ol);
 			o += il - ol;
 			ol = s->period_size - s->playback1st_size;
 		}
 		l += il;
 	}
 	if (iu == sk->completed_inurb) {
 		if (l != s->period_size)
 			printk(KERN_DEBUG"%s:%i %i\n", __func__, __LINE__,
 			       l/(int)s->cfg.frame_size);

 		return;
 	}
 second:
 	iu = sk->completed_inurb;
 	id = iu->iso_frame_desc;
 	p = 0;
 	goto loop;

 }
 #else
 static void loop_back(struct usb_stream *s)
 {
 }
 #endif

 static void stream_idle(struct usb_stream_kernel *sk,
 			struct urb *inurb, struct urb *outurb)
 {
 	struct usb_stream *s = sk->s;
 	int l, p;
 	int insize = s->idle_insize;
 	int urb_size = 0;

 	s->inpacket_split = s->next_inpacket_split;
 	s->inpacket_split_at = s->next_inpacket_split_at;
 	s->next_inpacket_split = -1;
 	s->next_inpacket_split_at = 0;

 	for (p = 0; p < inurb->number_of_packets; ++p) {
 		struct usb_iso_packet_descriptor *id = inurb->iso_frame_desc;
 		l = id[p].actual_length;
 		if (unlikely(l == 0 || id[p].status)) {
 			snd_printk(KERN_WARNING "underrun, status=%u\n",
 				   id[p].status);
 			goto err_out;
 		}
 		s->inpacket_head++;
 		s->inpacket_head %= s->inpackets;
 		if (s->inpacket_split == -1)
 			s->inpacket_split = s->inpacket_head;

 		s->inpacket[s->inpacket_head].offset =
 			id[p].offset + (inurb->transfer_buffer - (void *)s);
 		s->inpacket[s->inpacket_head].length = l;
 		if (insize + l > s->period_size &&
 		    s->next_inpacket_split == -1) {
 			s->next_inpacket_split = s->inpacket_head;
 			s->next_inpacket_split_at = s->period_size - insize;
 		}
 		insize += l;
 		urb_size += l;
 	}
 	s->idle_insize += urb_size - s->period_size;
 	if (s->idle_insize < 0) {
 		snd_printk(KERN_WARNING "%i\n",
 			   (s->idle_insize)/(int)s->cfg.frame_size);
 		goto err_out;
 	}
 	s->insize_done += urb_size;

 	l = s->idle_outsize;
 	s->outpacket[0].offset = (sk->idle_outurb->transfer_buffer -
 				  sk->write_page) - l;

 	if (usb_stream_prepare_playback(sk, inurb) < 0)
 		goto err_out;

 	s->outpacket[0].length = sk->idle_outurb->transfer_buffer_length + l;
 	s->outpacket[1].offset = sk->completed_outurb->transfer_buffer -
 		sk->write_page;

 	if (submit_urbs(sk, inurb, outurb) < 0)
 		goto err_out;

 	loop_back(s);
 	s->periods_done++;
 	wake_up_all(&sk->sleep);
 	return;
 err_out:
 	s->state = usb_stream_xrun;
 	wake_up_all(&sk->sleep);
 }

 static void i_capture_idle(struct urb *urb)
 {
 	struct usb_stream_kernel *sk = urb->context;
 	if (balance_capture(sk, urb))
 		stream_idle(sk, urb, sk->i_urb);
 }

 static void i_playback_idle(struct urb *urb)
 {
 	struct usb_stream_kernel *sk = urb->context;
 	if (balance_playback(sk, urb))
 		stream_idle(sk, sk->i_urb, urb);
 }

 static void stream_start(struct usb_stream_kernel *sk,
 			 struct urb *inurb, struct urb *outurb)
 {
 	struct usb_stream *s = sk->s;
 	if (s->state >= usb_stream_sync1) {
 		int l, p, max_diff, max_diff_0;
 		int urb_size = 0;
 		unsigned frames_per_packet, min_frames = 0;
 		frames_per_packet = (s->period_size - s->idle_insize);
 		frames_per_packet <<= 8;
 		frames_per_packet /=
 			s->cfg.frame_size * inurb->number_of_packets;
 		frames_per_packet++;

 		max_diff_0 = s->cfg.frame_size;
 		if (s->cfg.period_frames >= 256)
 			max_diff_0 <<= 1;
 		if (s->cfg.period_frames >= 1024)
 			max_diff_0 <<= 1;
 		max_diff = max_diff_0;
 		for (p = 0; p < inurb->number_of_packets; ++p) {
 			int diff;
 			l = inurb->iso_frame_desc[p].actual_length;
 			urb_size += l;

 			min_frames += frames_per_packet;
 			diff = urb_size -
 				(min_frames >> 8) * s->cfg.frame_size;
 			if (diff < max_diff) {
 				snd_printdd(KERN_DEBUG "%i %i %i %i\n",
 					    s->insize_done,
 					    urb_size / (int)s->cfg.frame_size,
 					    inurb->number_of_packets, diff);
 				max_diff = diff;
 			}
 		}
 		s->idle_insize -= max_diff - max_diff_0;
 		s->idle_insize += urb_size - s->period_size;
 		if (s->idle_insize < 0) {
 			snd_printk("%i %i %i\n",
 				   s->idle_insize, urb_size, s->period_size);
 			return;
 		} else if (s->idle_insize == 0) {
 			s->next_inpacket_split =
 				(s->inpacket_head + 1) % s->inpackets;
 			s->next_inpacket_split_at = 0;
 		} else {
 			unsigned split = s->inpacket_head;
 			l = s->idle_insize;
 			while (l > s->inpacket[split].length) {
 				l -= s->inpacket[split].length;
 				if (split == 0)
 					split = s->inpackets - 1;
 				else
 					split--;
 			}
 			s->next_inpacket_split = split;
 			s->next_inpacket_split_at =
 				s->inpacket[split].length - l;
 		}

 		s->insize_done += urb_size;

 		if (usb_stream_prepare_playback(sk, inurb) < 0)
 			return;

 	} else
 		playback_prep_freqn(sk, sk->idle_outurb);

 	if (submit_urbs(sk, inurb, outurb) < 0)
 		return;

 	if (s->state == usb_stream_sync1 && s->insize_done > 360000) {
 		/* just guesswork                            ^^^^^^ */
 		s->state = usb_stream_ready;
 		subs_set_complete(sk->inurb, i_capture_idle);
 		subs_set_complete(sk->outurb, i_playback_idle);
 	}
 }

 static void i_capture_start(struct urb *urb)
 {
 	struct usb_iso_packet_descriptor *id = urb->iso_frame_desc;
 	struct usb_stream_kernel *sk = urb->context;
 	struct usb_stream *s = sk->s;
 	int p;
 	int empty = 0;

 	if (urb->status) {
 		snd_printk(KERN_WARNING "status=%i\n", urb->status);
 		return;
 	}

 	for (p = 0; p < urb->number_of_packets; ++p) {
 		int l = id[p].actual_length;
 		if (l < s->cfg.frame_size) {
 			++empty;
 			if (s->state >= usb_stream_sync0) {
 				snd_printk(KERN_WARNING "%i\n", l);
 				return;
 			}
 		}
 		s->inpacket_head++;
 		s->inpacket_head %= s->inpackets;
 		s->inpacket[s->inpacket_head].offset =
 			id[p].offset + (urb->transfer_buffer - (void *)s);
 		s->inpacket[s->inpacket_head].length = l;
 	}
 #ifdef SHOW_EMPTY
 	if (empty) {
 		printk(KERN_DEBUG"%s:%i: %i", __func__, __LINE__,
 		       urb->iso_frame_desc[0].actual_length);
 		for (pack = 1; pack < urb->number_of_packets; ++pack) {
 			int l = urb->iso_frame_desc[pack].actual_length;
 			printk(" %i", l);
 		}
 		printk("\n");
 	}
 #endif
 	if (!empty && s->state < usb_stream_sync1)
 		++s->state;

 	if (balance_capture(sk, urb))
 		stream_start(sk, urb, sk->i_urb);
 }

 static void i_playback_start(struct urb *urb)
 {
 	struct usb_stream_kernel *sk = urb->context;
 	if (balance_playback(sk, urb))
 		stream_start(sk, sk->i_urb, urb);
 }

 int usb_stream_start(struct usb_stream_kernel *sk)
 {
 	struct usb_stream *s = sk->s;
 	int frame = 0, iters = 0;
 	int u, err;
 	int try = 0;

 	if (s->state != usb_stream_stopped)
 		return -EAGAIN;

 	subs_set_complete(sk->inurb, i_capture_start);
 	subs_set_complete(sk->outurb, i_playback_start);
 	memset(sk->write_page, 0, s->write_size);
 dotry:
 	s->insize_done = 0;
 	s->idle_insize = 0;
 	s->idle_outsize = 0;
 	s->sync_packet = -1;
 	s->inpacket_head = -1;
 	sk->iso_frame_balance = 0;
 	++try;
 	for (u = 0; u < 2; u++) {
 		struct urb *inurb = sk->inurb[u];
 		struct urb *outurb = sk->outurb[u];
 		playback_prep_freqn(sk, outurb);
 		inurb->number_of_packets = outurb->number_of_packets;
 		inurb->transfer_buffer_length =
 			inurb->number_of_packets *
 			inurb->iso_frame_desc[0].length;
 		preempt_disable();
 		if (u == 0) {
 			int now;
 			struct usb_device *dev = inurb->dev;
 			frame = usb_get_current_frame_number(dev);
 			do {
 				now = usb_get_current_frame_number(dev);
 				++iters;
 			} while (now > -1 && now == frame);
 		}
 		err = usb_submit_urb(inurb, GFP_ATOMIC);
 		if (err < 0) {
 			preempt_enable();
 			snd_printk(KERN_ERR"usb_submit_urb(sk->inurb[%i])"
 				   " returned %i\n", u, err);
 			return err;
 		}
 		err = usb_submit_urb(outurb, GFP_ATOMIC);
 		if (err < 0) {
 			preempt_enable();
 			snd_printk(KERN_ERR"usb_submit_urb(sk->outurb[%i])"
 				   " returned %i\n", u, err);
 			return err;
 		}
 		preempt_enable();
 		if (inurb->start_frame != outurb->start_frame) {
 			snd_printd(KERN_DEBUG
 				   "u[%i] start_frames differ in:%u out:%u\n",
 				   u, inurb->start_frame, outurb->start_frame);
 			goto check_retry;
 		}
 	}
 	snd_printdd(KERN_DEBUG "%i %i\n", frame, iters);
 	try = 0;
 check_retry:
 	if (try) {
 		usb_stream_stop(sk);
 		if (try < 5) {
 			msleep(1500);
 			snd_printd(KERN_DEBUG "goto dotry;\n");
 			goto dotry;
 		}
 		snd_printk(KERN_WARNING"couldn't start"
 			   " all urbs on the same start_frame.\n");
 		return -EFAULT;
 	}

 	sk->idle_inurb = sk->inurb[USB_STREAM_NURBS - 2];
 	sk->idle_outurb = sk->outurb[USB_STREAM_NURBS - 2];
 	sk->completed_inurb = sk->inurb[USB_STREAM_NURBS - 1];
 	sk->completed_outurb = sk->outurb[USB_STREAM_NURBS - 1];

 /* wait, check */
 	{
 		int wait_ms = 3000;
 		while (s->state != usb_stream_ready && wait_ms > 0) {
 			snd_printdd(KERN_DEBUG "%i\n", s->state);
 			msleep(200);
 			wait_ms -= 200;
 		}
 	}

 	return s->state == usb_stream_ready ? 0 : -EFAULT;
 }


 /*                             stop                                   */

 void usb_stream_stop(struct usb_stream_kernel *sk)
 {
 	int u;
 	if (!sk->s)
 		return;
 	for (u = 0; u < USB_STREAM_NURBS; ++u) {
 		usb_kill_urb(sk->inurb[u]);
 		usb_kill_urb(sk->outurb[u]);
 	}
 	sk->s->state = usb_stream_stopped;
 	msleep(400);
 }
	/*
	* Copyright (C) 2007, 2008 Karsten Wiese <fzu@wemgehoertderstaat.de>
	*
	* This program is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License as published by the
	* Free Software Foundation; either version 2 of the License, or (at your
	* option) any later version.
	*
	* This program is distributed in the hope that it will be useful, but
	* WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
	* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
	* for more details.
	*
	* You should have received a copy of the GNU General Public License
	* along with this program; if not, write to the Free Software Foundation,
	* Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
	*/

	#include <linux/usb.h>

	#include "usb_stream.h"


	/* setup */

	static unsigned usb_stream_next_packet_size(struct usb_stream_kernel *sk)
	{
	struct usb_stream *s = sk->s;
	sk->out_phase_peeked = (sk->out_phase & 0xffff) + sk->freqn;
	return (sk->out_phase_peeked >> 16) * s->cfg.frame_size;
	}

	static void playback_prep_freqn(struct usb_stream_kernel sk, struct urb urb)
	{
	struct usb_stream *s = sk->s;
	unsigned l = 0;
	int pack;

	urb->iso_frame_desc[0].offset = 0;
	urb->iso_frame_desc[0].length = usb_stream_next_packet_size(sk);
	sk->out_phase = sk->out_phase_peeked;
	urb->transfer_buffer_length = urb->iso_frame_desc[0].length;

	for (pack = 1; pack < sk->n_o_ps; pack++) {
	l = usb_stream_next_packet_size(sk);
	if (s->idle_outsize + urb->transfer_buffer_length + l >
	s->period_size)
	goto check;

	sk->out_phase = sk->out_phase_peeked;
	urb->iso_frame_desc[pack].offset = urb->transfer_buffer_length;
	urb->iso_frame_desc[pack].length = l;
	urb->transfer_buffer_length += l;
	}
	snd_printdd(KERN_DEBUG "%i\n", urb->transfer_buffer_length);

	check:
	urb->number_of_packets = pack;
	s->idle_outsize += urb->transfer_buffer_length - s->period_size;
	snd_printdd(KERN_DEBUG "idle=%i ul=%i ps=%i\n", s->idle_outsize,
	urb->transfer_buffer_length, s->period_size);
	}

	static void init_pipe_urbs(struct usb_stream_kernel *sk, unsigned use_packsize,
	struct urb *urbs, char transfer,
	struct usb_device *dev, int pipe)
	{
	int u, p;
	int maxpacket = use_packsize ?
	use_packsize : usb_maxpacket(dev, pipe, usb_pipeout(pipe));
	int transfer_length = maxpacket * sk->n_o_ps;

	for (u = 0; u < USB_STREAM_NURBS;
	++u, transfer += transfer_length) {
	struct urb *urb = urbs[u];
	struct usb_iso_packet_descriptor *desc;
	urb->transfer_flags = URB_ISO_ASAP;
	urb->transfer_buffer = transfer;
	urb->dev = dev;
	urb->pipe = pipe;
	urb->number_of_packets = sk->n_o_ps;
	urb->context = sk;
	urb->interval = 1;
	if (usb_pipeout(pipe))
	continue;

	urb->transfer_buffer_length = transfer_length;
	desc = urb->iso_frame_desc;
	desc->offset = 0;
	desc->length = maxpacket;
	for (p = 1; p < sk->n_o_ps; ++p) {
	desc[p].offset = desc[p - 1].offset + maxpacket;
	desc[p].length = maxpacket;
	}
	}
	}

	static void init_urbs(struct usb_stream_kernel *sk, unsigned use_packsize,
	struct usb_device *dev, int in_pipe, int out_pipe)
	{
	struct usb_stream *s = sk->s;
	char indata = (char )s + sizeof(*s) +
	sizeof(struct usb_stream_packet) *
	s->inpackets;
	int u;

	for (u = 0; u < USB_STREAM_NURBS; ++u) {
	sk->inurb[u] = usb_alloc_urb(sk->n_o_ps, GFP_KERNEL);
	sk->outurb[u] = usb_alloc_urb(sk->n_o_ps, GFP_KERNEL);
	}

	init_pipe_urbs(sk, use_packsize, sk->inurb, indata, dev, in_pipe);
	init_pipe_urbs(sk, use_packsize, sk->outurb, sk->write_page, dev,
	out_pipe);
	}


	/*
	* convert a sampling rate into our full speed format (fs/1000 in Q16.16)
	* this will overflow at approx 524 kHz
	*/
	static inline unsigned get_usb_full_speed_rate(unsigned rate)
	{
	return ((rate << 13) + 62) / 125;
	}

	/*
	* convert a sampling rate into USB high speed format (fs/8000 in Q16.16)
	* this will overflow at approx 4 MHz
	*/
	static inline unsigned get_usb_high_speed_rate(unsigned rate)
	{
	return ((rate << 10) + 62) / 125;
	}

	void usb_stream_free(struct usb_stream_kernel *sk)
	{
	struct usb_stream *s;
	unsigned u;

	for (u = 0; u < USB_STREAM_NURBS; ++u) {
	usb_free_urb(sk->inurb[u]);
	sk->inurb[u] = NULL;
	usb_free_urb(sk->outurb[u]);
	sk->outurb[u] = NULL;
	}

	s = sk->s;
	if (!s)
	return;

	free_pages((unsigned long)sk->write_page, get_order(s->write_size));
	sk->write_page = NULL;
	free_pages((unsigned long)s, get_order(s->read_size));
	sk->s = NULL;
	}

	struct usb_stream usb_stream_new(struct usb_stream_kernel sk,
	struct usb_device *dev,
	unsigned in_endpoint, unsigned out_endpoint,
	unsigned sample_rate, unsigned use_packsize,
	unsigned period_frames, unsigned frame_size)
	{
	int packets, max_packsize;
	int in_pipe, out_pipe;
	int read_size = sizeof(struct usb_stream);
	int write_size;
	int usb_frames = dev->speed == USB_SPEED_HIGH ? 8000 : 1000;
	int pg;

	in_pipe = usb_rcvisocpipe(dev, in_endpoint);
	out_pipe = usb_sndisocpipe(dev, out_endpoint);

	max_packsize = use_packsize ?
	use_packsize : usb_maxpacket(dev, in_pipe, 0);

	/*
	t_period = period_frames / sample_rate
	iso_packs = t_period / t_iso_frame
	= (period_frames / sample_rate) * (1 / t_iso_frame)
	*/

	packets = period_frames * usb_frames / sample_rate + 1;

	if (dev->speed == USB_SPEED_HIGH)
	packets = (packets + 7) & ~7;

	read_size += packets * USB_STREAM_URBDEPTH *
	(max_packsize + sizeof(struct usb_stream_packet));

	max_packsize = usb_maxpacket(dev, out_pipe, 1);
	write_size = max_packsize * packets * USB_STREAM_URBDEPTH;

	if (read_size >= 256PAGE_SIZE \|\| write_size >= 256PAGE_SIZE) {
	snd_printk(KERN_WARNING "a size exceeds 128*PAGE_SIZE\n");
	goto out;
	}

	pg = get_order(read_size);
	sk->s = (void *) __get_free_pages(GFP_KERNEL\|__GFP_COMP\|__GFP_ZERO, pg);
	if (!sk->s) {
	snd_printk(KERN_WARNING "couldn't __get_free_pages()\n");
	goto out;
	}
	sk->s->cfg.version = USB_STREAM_INTERFACE_VERSION;

	sk->s->read_size = read_size;

	sk->s->cfg.sample_rate = sample_rate;
	sk->s->cfg.frame_size = frame_size;
	sk->n_o_ps = packets;
	sk->s->inpackets = packets * USB_STREAM_URBDEPTH;
	sk->s->cfg.period_frames = period_frames;
	sk->s->period_size = frame_size * period_frames;

	sk->s->write_size = write_size;
	pg = get_order(write_size);

	sk->write_page =
	(void *)__get_free_pages(GFP_KERNEL\|__GFP_COMP\|__GFP_ZERO, pg);
	if (!sk->write_page) {
	snd_printk(KERN_WARNING "couldn't __get_free_pages()\n");
	usb_stream_free(sk);
	return NULL;
	}

	/* calculate the frequency in 16.16 format */
	if (dev->speed == USB_SPEED_FULL)
	sk->freqn = get_usb_full_speed_rate(sample_rate);
	else
	sk->freqn = get_usb_high_speed_rate(sample_rate);

	init_urbs(sk, use_packsize, dev, in_pipe, out_pipe);
	sk->s->state = usb_stream_stopped;
	out:
	return sk->s;
	}


	/* start */

	static bool balance_check(struct usb_stream_kernel sk, struct urb urb)
	{
	bool r;
	if (unlikely(urb->status)) {
	if (urb->status != -ESHUTDOWN && urb->status != -ENOENT)
	snd_printk(KERN_WARNING "status=%i\n", urb->status);
	sk->iso_frame_balance = 0x7FFFFFFF;
	return false;
	}
	r = sk->iso_frame_balance == 0;
	if (!r)
	sk->i_urb = urb;
	return r;
	}

	static bool balance_playback(struct usb_stream_kernel sk, struct urb urb)
	{
	sk->iso_frame_balance += urb->number_of_packets;
	return balance_check(sk, urb);
	}

	static bool balance_capture(struct usb_stream_kernel sk, struct urb urb)
	{
	sk->iso_frame_balance -= urb->number_of_packets;
	return balance_check(sk, urb);
	}

	static void subs_set_complete(struct urb *urbs, void (complete)(struct urb *))
	{
	int u;

	for (u = 0; u < USB_STREAM_NURBS; u++) {
	struct urb *urb = urbs[u];
	urb->complete = complete;
	}
	}

	static int usb_stream_prepare_playback(struct usb_stream_kernel *sk,
	struct urb *inurb)
	{
	struct usb_stream *s = sk->s;
	struct urb *io;
	struct usb_iso_packet_descriptor id, od;
	int p, l = 0;

	io = sk->idle_outurb;
	od = io->iso_frame_desc;
	io->transfer_buffer_length = 0;

	for (p = 0; s->sync_packet < 0; ++p, ++s->sync_packet) {
	struct urb *ii = sk->completed_inurb;
	id = ii->iso_frame_desc +
	ii->number_of_packets + s->sync_packet;
	l = id->actual_length;

	od[p].length = l;
	od[p].offset = io->transfer_buffer_length;
	io->transfer_buffer_length += l;
	}

	for (;
	s->sync_packet < inurb->number_of_packets && p < sk->n_o_ps;
	++p, ++s->sync_packet) {
	l = inurb->iso_frame_desc[s->sync_packet].actual_length;

	if (s->idle_outsize + io->transfer_buffer_length + l >
	s->period_size)
	goto check_ok;

	od[p].length = l;
	od[p].offset = io->transfer_buffer_length;
	io->transfer_buffer_length += l;
	}

	check_ok:
	s->sync_packet -= inurb->number_of_packets;
	if (s->sync_packet < -2 \|\| s->sync_packet > 0) {
	snd_printk(KERN_WARNING "invalid sync_packet = %i;"
	" p=%i nop=%i %i %x %x %x > %x\n",
	s->sync_packet, p, inurb->number_of_packets,
	s->idle_outsize + io->transfer_buffer_length + l,
	s->idle_outsize, io->transfer_buffer_length, l,
	s->period_size);
	return -1;
	}
	if (io->transfer_buffer_length % s->cfg.frame_size) {
	snd_printk(KERN_WARNING"invalid outsize = %i\n",
	io->transfer_buffer_length);
	return -1;
	}
	s->idle_outsize += io->transfer_buffer_length - s->period_size;
	io->number_of_packets = p;
	if (s->idle_outsize > 0) {
	snd_printk(KERN_WARNING "idle=%i\n", s->idle_outsize);
	return -1;
	}
	return 0;
	}

	static void prepare_inurb(int number_of_packets, struct urb *iu)
	{
	struct usb_iso_packet_descriptor *id;
	int p;

	iu->number_of_packets = number_of_packets;
	id = iu->iso_frame_desc;
	id->offset = 0;
	for (p = 0; p < iu->number_of_packets - 1; ++p)
	id[p + 1].offset = id[p].offset + id[p].length;

	iu->transfer_buffer_length =
	id[0].length * iu->number_of_packets;
	}

	static int submit_urbs(struct usb_stream_kernel *sk,
	struct urb inurb, struct urb outurb)
	{
	int err;
	prepare_inurb(sk->idle_outurb->number_of_packets, sk->idle_inurb);
	err = usb_submit_urb(sk->idle_inurb, GFP_ATOMIC);
	if (err < 0) {
	snd_printk(KERN_ERR "%i\n", err);
	return err;
	}
	sk->idle_inurb = sk->completed_inurb;
	sk->completed_inurb = inurb;
	err = usb_submit_urb(sk->idle_outurb, GFP_ATOMIC);
	if (err < 0) {
	snd_printk(KERN_ERR "%i\n", err);
	return err;
	}
	sk->idle_outurb = sk->completed_outurb;
	sk->completed_outurb = outurb;
	return 0;
	}

	#ifdef DEBUG_LOOP_BACK
	/*
	This loop_back() shows how to read/write the period data.
	*/
	static void loop_back(struct usb_stream *s)
	{
	char i, o;
	int il, ol, l, p;
	struct urb *iu;
	struct usb_iso_packet_descriptor *id;

	o = s->playback1st_to;
	ol = s->playback1st_size;
	l = 0;

	if (s->insplit_pack >= 0) {
	iu = sk->idle_inurb;
	id = iu->iso_frame_desc;
	p = s->insplit_pack;
	} else
	goto second;
	loop:
	for (; p < iu->number_of_packets && l < s->period_size; ++p) {
	i = iu->transfer_buffer + id[p].offset;
	il = id[p].actual_length;
	if (l + il > s->period_size)
	il = s->period_size - l;
	if (il <= ol) {
	memcpy(o, i, il);
	o += il;
	ol -= il;
	} else {
	memcpy(o, i, ol);
	singen_6pack(o, ol);
	o = s->playback_to;
	memcpy(o, i + ol, il - ol);
	o += il - ol;
	ol = s->period_size - s->playback1st_size;
	}
	l += il;
	}
	if (iu == sk->completed_inurb) {
	if (l != s->period_size)
	printk(KERN_DEBUG"%s:%i %i\n", __func__, __LINE__,
	l/(int)s->cfg.frame_size);

	return;
	}
	second:
	iu = sk->completed_inurb;
	id = iu->iso_frame_desc;
	p = 0;
	goto loop;

	}
	#else
	static void loop_back(struct usb_stream *s)
	{
	}
	#endif

	static void stream_idle(struct usb_stream_kernel *sk,
	struct urb inurb, struct urb outurb)
	{
	struct usb_stream *s = sk->s;
	int l, p;
	int insize = s->idle_insize;
	int urb_size = 0;

	s->inpacket_split = s->next_inpacket_split;
	s->inpacket_split_at = s->next_inpacket_split_at;
	s->next_inpacket_split = -1;
	s->next_inpacket_split_at = 0;

	for (p = 0; p < inurb->number_of_packets; ++p) {
	struct usb_iso_packet_descriptor *id = inurb->iso_frame_desc;
	l = id[p].actual_length;
	if (unlikely(l == 0 \|\| id[p].status)) {
	snd_printk(KERN_WARNING "underrun, status=%u\n",
	id[p].status);
	goto err_out;
	}
	s->inpacket_head++;
	s->inpacket_head %= s->inpackets;
	if (s->inpacket_split == -1)
	s->inpacket_split = s->inpacket_head;

	s->inpacket[s->inpacket_head].offset =
	id[p].offset + (inurb->transfer_buffer - (void *)s);
	s->inpacket[s->inpacket_head].length = l;
	if (insize + l > s->period_size &&
	s->next_inpacket_split == -1) {
	s->next_inpacket_split = s->inpacket_head;
	s->next_inpacket_split_at = s->period_size - insize;
	}
	insize += l;
	urb_size += l;
	}
	s->idle_insize += urb_size - s->period_size;
	if (s->idle_insize < 0) {
	snd_printk(KERN_WARNING "%i\n",
	(s->idle_insize)/(int)s->cfg.frame_size);
	goto err_out;
	}
	s->insize_done += urb_size;

	l = s->idle_outsize;
	s->outpacket[0].offset = (sk->idle_outurb->transfer_buffer -
	sk->write_page) - l;

	if (usb_stream_prepare_playback(sk, inurb) < 0)
	goto err_out;

	s->outpacket[0].length = sk->idle_outurb->transfer_buffer_length + l;
	s->outpacket[1].offset = sk->completed_outurb->transfer_buffer -
	sk->write_page;

	if (submit_urbs(sk, inurb, outurb) < 0)
	goto err_out;

	loop_back(s);
	s->periods_done++;
	wake_up_all(&sk->sleep);
	return;
	err_out:
	s->state = usb_stream_xrun;
	wake_up_all(&sk->sleep);
	}

	static void i_capture_idle(struct urb *urb)
	{
	struct usb_stream_kernel *sk = urb->context;
	if (balance_capture(sk, urb))
	stream_idle(sk, urb, sk->i_urb);
	}

	static void i_playback_idle(struct urb *urb)
	{
	struct usb_stream_kernel *sk = urb->context;
	if (balance_playback(sk, urb))
	stream_idle(sk, sk->i_urb, urb);
	}

	static void stream_start(struct usb_stream_kernel *sk,
	struct urb inurb, struct urb outurb)
	{
	struct usb_stream *s = sk->s;
	if (s->state >= usb_stream_sync1) {
	int l, p, max_diff, max_diff_0;
	int urb_size = 0;
	unsigned frames_per_packet, min_frames = 0;
	frames_per_packet = (s->period_size - s->idle_insize);
	frames_per_packet <<= 8;
	frames_per_packet /=
	s->cfg.frame_size * inurb->number_of_packets;
	frames_per_packet++;

	max_diff_0 = s->cfg.frame_size;
	if (s->cfg.period_frames >= 256)
	max_diff_0 <<= 1;
	if (s->cfg.period_frames >= 1024)
	max_diff_0 <<= 1;
	max_diff = max_diff_0;
	for (p = 0; p < inurb->number_of_packets; ++p) {
	int diff;
	l = inurb->iso_frame_desc[p].actual_length;
	urb_size += l;

	min_frames += frames_per_packet;
	diff = urb_size -
	(min_frames >> 8) * s->cfg.frame_size;
	if (diff < max_diff) {
	snd_printdd(KERN_DEBUG "%i %i %i %i\n",
	s->insize_done,
	urb_size / (int)s->cfg.frame_size,
	inurb->number_of_packets, diff);
	max_diff = diff;
	}
	}
	s->idle_insize -= max_diff - max_diff_0;
	s->idle_insize += urb_size - s->period_size;
	if (s->idle_insize < 0) {
	snd_printk("%i %i %i\n",
	s->idle_insize, urb_size, s->period_size);
	return;
	} else if (s->idle_insize == 0) {
	s->next_inpacket_split =
	(s->inpacket_head + 1) % s->inpackets;
	s->next_inpacket_split_at = 0;
	} else {
	unsigned split = s->inpacket_head;
	l = s->idle_insize;
	while (l > s->inpacket[split].length) {
	l -= s->inpacket[split].length;
	if (split == 0)
	split = s->inpackets - 1;
	else
	split--;
	}
	s->next_inpacket_split = split;
	s->next_inpacket_split_at =
	s->inpacket[split].length - l;
	}

	s->insize_done += urb_size;

	if (usb_stream_prepare_playback(sk, inurb) < 0)
	return;

	} else
	playback_prep_freqn(sk, sk->idle_outurb);

	if (submit_urbs(sk, inurb, outurb) < 0)
	return;

	if (s->state == usb_stream_sync1 && s->insize_done > 360000) {
	/* just guesswork ^^^^^^ */
	s->state = usb_stream_ready;
	subs_set_complete(sk->inurb, i_capture_idle);
	subs_set_complete(sk->outurb, i_playback_idle);
	}
	}

	static void i_capture_start(struct urb *urb)
	{
	struct usb_iso_packet_descriptor *id = urb->iso_frame_desc;
	struct usb_stream_kernel *sk = urb->context;
	struct usb_stream *s = sk->s;
	int p;
	int empty = 0;

	if (urb->status) {
	snd_printk(KERN_WARNING "status=%i\n", urb->status);
	return;
	}

	for (p = 0; p < urb->number_of_packets; ++p) {
	int l = id[p].actual_length;
	if (l < s->cfg.frame_size) {
	++empty;
	if (s->state >= usb_stream_sync0) {
	snd_printk(KERN_WARNING "%i\n", l);
	return;
	}
	}
	s->inpacket_head++;
	s->inpacket_head %= s->inpackets;
	s->inpacket[s->inpacket_head].offset =
	id[p].offset + (urb->transfer_buffer - (void *)s);
	s->inpacket[s->inpacket_head].length = l;
	}
	#ifdef SHOW_EMPTY
	if (empty) {
	printk(KERN_DEBUG"%s:%i: %i", __func__, __LINE__,
	urb->iso_frame_desc[0].actual_length);
	for (pack = 1; pack < urb->number_of_packets; ++pack) {
	int l = urb->iso_frame_desc[pack].actual_length;
	printk(" %i", l);
	}
	printk("\n");
	}
	#endif
	if (!empty && s->state < usb_stream_sync1)
	++s->state;

	if (balance_capture(sk, urb))
	stream_start(sk, urb, sk->i_urb);
	}

	static void i_playback_start(struct urb *urb)
	{
	struct usb_stream_kernel *sk = urb->context;
	if (balance_playback(sk, urb))
	stream_start(sk, sk->i_urb, urb);
	}

	int usb_stream_start(struct usb_stream_kernel *sk)
	{
	struct usb_stream *s = sk->s;
	int frame = 0, iters = 0;
	int u, err;
	int try = 0;

	if (s->state != usb_stream_stopped)
	return -EAGAIN;

	subs_set_complete(sk->inurb, i_capture_start);
	subs_set_complete(sk->outurb, i_playback_start);
	memset(sk->write_page, 0, s->write_size);
	dotry:
	s->insize_done = 0;
	s->idle_insize = 0;
	s->idle_outsize = 0;
	s->sync_packet = -1;
	s->inpacket_head = -1;
	sk->iso_frame_balance = 0;
	++try;
	for (u = 0; u < 2; u++) {
	struct urb *inurb = sk->inurb[u];
	struct urb *outurb = sk->outurb[u];
	playback_prep_freqn(sk, outurb);
	inurb->number_of_packets = outurb->number_of_packets;
	inurb->transfer_buffer_length =
	inurb->number_of_packets *
	inurb->iso_frame_desc[0].length;
	preempt_disable();
	if (u == 0) {
	int now;
	struct usb_device *dev = inurb->dev;
	frame = usb_get_current_frame_number(dev);
	do {
	now = usb_get_current_frame_number(dev);
	++iters;
	} while (now > -1 && now == frame);
	}
	err = usb_submit_urb(inurb, GFP_ATOMIC);
	if (err < 0) {
	preempt_enable();
	snd_printk(KERN_ERR"usb_submit_urb(sk->inurb[%i])"
	" returned %i\n", u, err);
	return err;
	}
	err = usb_submit_urb(outurb, GFP_ATOMIC);
	if (err < 0) {
	preempt_enable();
	snd_printk(KERN_ERR"usb_submit_urb(sk->outurb[%i])"
	" returned %i\n", u, err);
	return err;
	}
	preempt_enable();
	if (inurb->start_frame != outurb->start_frame) {
	snd_printd(KERN_DEBUG
	"u[%i] start_frames differ in:%u out:%u\n",
	u, inurb->start_frame, outurb->start_frame);
	goto check_retry;
	}
	}
	snd_printdd(KERN_DEBUG "%i %i\n", frame, iters);
	try = 0;
	check_retry:
	if (try) {
	usb_stream_stop(sk);
	if (try < 5) {
	msleep(1500);
	snd_printd(KERN_DEBUG "goto dotry;\n");
	goto dotry;
	}
	snd_printk(KERN_WARNING"couldn't start"
	" all urbs on the same start_frame.\n");
	return -EFAULT;
	}

	sk->idle_inurb = sk->inurb[USB_STREAM_NURBS - 2];
	sk->idle_outurb = sk->outurb[USB_STREAM_NURBS - 2];
	sk->completed_inurb = sk->inurb[USB_STREAM_NURBS - 1];
	sk->completed_outurb = sk->outurb[USB_STREAM_NURBS - 1];

	/* wait, check */
	{
	int wait_ms = 3000;
	while (s->state != usb_stream_ready && wait_ms > 0) {
	snd_printdd(KERN_DEBUG "%i\n", s->state);
	msleep(200);
	wait_ms -= 200;
	}
	}

	return s->state == usb_stream_ready ? 0 : -EFAULT;
	}


	/* stop */

	void usb_stream_stop(struct usb_stream_kernel *sk)
	{
	int u;
	if (!sk->s)
	return;
	for (u = 0; u < USB_STREAM_NURBS; ++u) {
	usb_kill_urb(sk->inurb[u]);
	usb_kill_urb(sk->outurb[u]);
	}
	sk->s->state = usb_stream_stopped;
	msleep(400);
	}