Linux Kernel  3.7.1
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helper.c
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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 #include "quirks.h"
25 
26 /*
27  * combine bytes and get an integer value
28  */
29 unsigned int snd_usb_combine_bytes(unsigned char *bytes, int size)
30 {
31  switch (size) {
32  case 1: return *bytes;
33  case 2: return combine_word(bytes);
34  case 3: return combine_triple(bytes);
35  case 4: return combine_quad(bytes);
36  default: return 0;
37  }
38 }
39 
40 /*
41  * parse descriptor buffer and return the pointer starting the given
42  * descriptor type.
43  */
44 void *snd_usb_find_desc(void *descstart, int desclen, void *after, u8 dtype)
45 {
46  u8 *p, *end, *next;
47 
48  p = descstart;
49  end = p + desclen;
50  for (; p < end;) {
51  if (p[0] < 2)
52  return NULL;
53  next = p + p[0];
54  if (next > end)
55  return NULL;
56  if (p[1] == dtype && (!after || (void *)p > after)) {
57  return p;
58  }
59  p = next;
60  }
61  return NULL;
62 }
63 
64 /*
65  * find a class-specified interface descriptor with the given subtype.
66  */
67 void *snd_usb_find_csint_desc(void *buffer, int buflen, void *after, u8 dsubtype)
68 {
69  unsigned char *p = after;
70 
71  while ((p = snd_usb_find_desc(buffer, buflen, p,
73  if (p[0] >= 3 && p[2] == dsubtype)
74  return p;
75  }
76  return NULL;
77 }
78 
79 /*
80  * Wrapper for usb_control_msg().
81  * Allocates a temp buffer to prevent dmaing from/to the stack.
82  */
83 int snd_usb_ctl_msg(struct usb_device *dev, unsigned int pipe, __u8 request,
84  __u8 requesttype, __u16 value, __u16 index, void *data,
85  __u16 size)
86 {
87  int err;
88  void *buf = NULL;
89 
90  if (size > 0) {
91  buf = kmemdup(data, size, GFP_KERNEL);
92  if (!buf)
93  return -ENOMEM;
94  }
95  err = usb_control_msg(dev, pipe, request, requesttype,
96  value, index, buf, size, 1000);
97  if (size > 0) {
98  memcpy(data, buf, size);
99  kfree(buf);
100  }
101 
102  snd_usb_ctl_msg_quirk(dev, pipe, request, requesttype,
103  value, index, data, size);
104 
105  return err;
106 }
107 
109  struct usb_host_interface *alts)
110 {
111  switch (snd_usb_get_speed(chip->dev)) {
112  case USB_SPEED_HIGH:
113  case USB_SPEED_SUPER:
114  if (get_endpoint(alts, 0)->bInterval >= 1 &&
115  get_endpoint(alts, 0)->bInterval <= 4)
116  return get_endpoint(alts, 0)->bInterval - 1;
117  break;
118  default:
119  break;
120  }
121  return 0;
122 }
123