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 #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,
  72                                       USB_DT_CS_INTERFACE)) != NULL) {
  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         int timeout;
  90
  91         if (size > 0) {
  92                 buf = kmemdup(data, size, GFP_KERNEL);
  93                 if (!buf)
  94                         return -ENOMEM;
  95         }
  96
  97         if (requesttype & USB_DIR_IN)
  98                 timeout = USB_CTRL_GET_TIMEOUT;
  99         else
 100                 timeout = USB_CTRL_SET_TIMEOUT;
 101
 102         err = usb_control_msg(dev, pipe, request, requesttype,
 103                               value, index, buf, size, timeout);
 104
 105         if (size > 0) {
 106                 memcpy(data, buf, size);
 107                 kfree(buf);
 108         }
 109
 110         snd_usb_ctl_msg_quirk(dev, pipe, request, requesttype,
 111                               value, index, data, size);
 112
 113         return err;
 114 }
 115
 116 unsigned char snd_usb_parse_datainterval(struct snd_usb_audio *chip,
 117                                          struct usb_host_interface *alts)
 118 {
 119         switch (snd_usb_get_speed(chip->dev)) {
 120         case USB_SPEED_HIGH:
 121         case USB_SPEED_SUPER:
 122                 if (get_endpoint(alts, 0)->bInterval >= 1 &&
 123                     get_endpoint(alts, 0)->bInterval <= 4)
 124                         return get_endpoint(alts, 0)->bInterval - 1;
 125                 break;
 126         default:
 127                 break;
 128         }
 129         return 0;
 130 }
 131