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helper.c

/*
 *   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., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
 *
 */

#include <linux/init.h>
#include <linux/slab.h>
#include <linux/usb.h>

#include "usbaudio.h"
#include "helper.h"

/*
 * combine bytes and get an integer value
 */
unsigned int snd_usb_combine_bytes(unsigned char *bytes, int size)
{
      switch (size) {
      case 1:  return *bytes;
      case 2:  return combine_word(bytes);
      case 3:  return combine_triple(bytes);
      case 4:  return combine_quad(bytes);
      default: return 0;
      }
}

/*
 * parse descriptor buffer and return the pointer starting the given
 * descriptor type.
 */
void *snd_usb_find_desc(void *descstart, int desclen, void *after, u8 dtype)
{
      u8 *p, *end, *next;

      p = descstart;
      end = p + desclen;
      for (; p < end;) {
            if (p[0] < 2)
                  return NULL;
            next = p + p[0];
            if (next > end)
                  return NULL;
            if (p[1] == dtype && (!after || (void *)p > after)) {
                  return p;
            }
            p = next;
      }
      return NULL;
}

/*
 * find a class-specified interface descriptor with the given subtype.
 */
void *snd_usb_find_csint_desc(void *buffer, int buflen, void *after, u8 dsubtype)
{
      unsigned char *p = after;

      while ((p = snd_usb_find_desc(buffer, buflen, p,
                              USB_DT_CS_INTERFACE)) != NULL) {
            if (p[0] >= 3 && p[2] == dsubtype)
                  return p;
      }
      return NULL;
}

/*
 * Wrapper for usb_control_msg().
 * Allocates a temp buffer to prevent dmaing from/to the stack.
 */
int snd_usb_ctl_msg(struct usb_device *dev, unsigned int pipe, __u8 request,
                __u8 requesttype, __u16 value, __u16 index, void *data,
                __u16 size, int timeout)
{
      int err;
      void *buf = NULL;

      if (size > 0) {
            buf = kmemdup(data, size, GFP_KERNEL);
            if (!buf)
                  return -ENOMEM;
      }
      err = usb_control_msg(dev, pipe, request, requesttype,
                        value, index, buf, size, timeout);
      if (size > 0) {
            memcpy(data, buf, size);
            kfree(buf);
      }
      return err;
}

unsigned char snd_usb_parse_datainterval(struct snd_usb_audio *chip,
                               struct usb_host_interface *alts)
{
      switch (snd_usb_get_speed(chip->dev)) {
      case USB_SPEED_HIGH:
      case USB_SPEED_SUPER:
            if (get_endpoint(alts, 0)->bInterval >= 1 &&
                get_endpoint(alts, 0)->bInterval <= 4)
                  return get_endpoint(alts, 0)->bInterval - 1;
            break;
      default:
            break;
      }
      return 0;
}


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