sound/usb/helper.c

   1 /*
   2  *   This program is free software; you can redistribute it and/or modify
   3  *   it under the terms of the GNU General Public License as published by
   4  *   the Free Software Foundation; either version 2 of the License, or
   5  *   (at your option) any later version.
   6  *
   7  *   This program is distributed in the hope that it will be useful,
   8  *   but WITHOUT ANY WARRANTY; without even the implied warranty of
   9  *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  10  *   GNU General Public License for more details.
  11  *
  12  *   You should have received a copy of the GNU General Public License
  13  *   along with this program; if not, write to the Free Software
  14  *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
  15  *
  16  */
  17
  18 #include <linux/init.h>
  19 #include <linux/slab.h>
  20 #include <linux/usb.h>
  21
  22 #include "usbaudio.h"
  23 #include "helper.h"
  24
  25 /*
  26  * combine bytes and get an integer value
  27  */
  28 unsigned int snd_usb_combine_bytes(unsigned char *bytes, int size)
  29 {
  30         switch (size) {
  31         case 1:  return *bytes;
  32         case 2:  return combine_word(bytes);
  33         case 3:  return combine_triple(bytes);
  34         case 4:  return combine_quad(bytes);
  35         default: return 0;
  36         }
  37 }
  38
  39 /*
  40  * parse descriptor buffer and return the pointer starting the given
  41  * descriptor type.
  42  */
  43 void *snd_usb_find_desc(void *descstart, int desclen, void *after, u8 dtype)
  44 {
  45         u8 *p, *end, *next;
  46
  47         p = descstart;
  48         end = p + desclen;
  49         for (; p < end;) {
  50                 if (p[0] < 2)
  51                         return NULL;
  52                 next = p + p[0];
  53                 if (next > end)
  54                         return NULL;
  55                 if (p[1] == dtype && (!after || (void *)p > after)) {
  56                         return p;
  57                 }
  58                 p = next;
  59         }
  60         return NULL;
  61 }
  62
  63 /*
  64  * find a class-specified interface descriptor with the given subtype.
  65  */
  66 void *snd_usb_find_csint_desc(void *buffer, int buflen, void *after, u8 dsubtype)
  67 {
  68         unsigned char *p = after;
  69
  70         while ((p = snd_usb_find_desc(buffer, buflen, p,
  71                                       USB_DT_CS_INTERFACE)) != NULL) {
  72                 if (p[0] >= 3 && p[2] == dsubtype)
  73                         return p;
  74         }
  75         return NULL;
  76 }
  77
  78 /*
  79  * Wrapper for usb_control_msg().
  80  * Allocates a temp buffer to prevent dmaing from/to the stack.
  81  */
  82 int snd_usb_ctl_msg(struct usb_device *dev, unsigned int pipe, __u8 request,
  83                     __u8 requesttype, __u16 value, __u16 index, void *data,
  84                     __u16 size, int timeout)
  85 {
  86         int err;
  87         void *buf = NULL;
  88
  89         if (size > 0) {
  90                 buf = kmemdup(data, size, GFP_KERNEL);
  91                 if (!buf)
  92                         return -ENOMEM;
  93         }
  94         err = usb_control_msg(dev, pipe, request, requesttype,
  95                               value, index, buf, size, timeout);
  96         if (size > 0) {
  97                 memcpy(data, buf, size);
  98                 kfree(buf);
  99         }
 100         return err;
 101 }
 102
 103 unsigned char snd_usb_parse_datainterval(struct snd_usb_audio *chip,
 104                                          struct usb_host_interface *alts)
 105 {
 106         switch (snd_usb_get_speed(chip->dev)) {
 107         case USB_SPEED_HIGH:
 108         case USB_SPEED_SUPER:
 109                 if (get_endpoint(alts, 0)->bInterval >= 1 &&
 110                     get_endpoint(alts, 0)->bInterval <= 4)
 111                         return get_endpoint(alts, 0)->bInterval - 1;
 112                 break;
 113         default:
 114                 break;
 115         }
 116         return 0;
 117 }
 118