sound/usb/helper.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  */
   4
   5 #include <linux/init.h>
   6 #include <linux/slab.h>
   7 #include <linux/usb.h>
   8
   9 #include "usbaudio.h"
  10 #include "helper.h"
  11 #include "quirks.h"
  12
  13 /*
  14  * combine bytes and get an integer value
  15  */
  16 unsigned int snd_usb_combine_bytes(unsigned char *bytes, int size)
  17 {
  18         switch (size) {
  19         case 1:  return *bytes;
  20         case 2:  return combine_word(bytes);
  21         case 3:  return combine_triple(bytes);
  22         case 4:  return combine_quad(bytes);
  23         default: return 0;
  24         }
  25 }
  26
  27 /*
  28  * parse descriptor buffer and return the pointer starting the given
  29  * descriptor type.
  30  */
  31 void *snd_usb_find_desc(void *descstart, int desclen, void *after, u8 dtype)
  32 {
  33         u8 *p, *end, *next;
  34
  35         p = descstart;
  36         end = p + desclen;
  37         for (; p < end;) {
  38                 if (p[0] < 2)
  39                         return NULL;
  40                 next = p + p[0];
  41                 if (next > end)
  42                         return NULL;
  43                 if (p[1] == dtype && (!after || (void *)p > after)) {
  44                         return p;
  45                 }
  46                 p = next;
  47         }
  48         return NULL;
  49 }
  50
  51 /*
  52  * find a class-specified interface descriptor with the given subtype.
  53  */
  54 void *snd_usb_find_csint_desc(void *buffer, int buflen, void *after, u8 dsubtype)
  55 {
  56         unsigned char *p = after;
  57
  58         while ((p = snd_usb_find_desc(buffer, buflen, p,
  59                                       USB_DT_CS_INTERFACE)) != NULL) {
  60                 if (p[0] >= 3 && p[2] == dsubtype)
  61                         return p;
  62         }
  63         return NULL;
  64 }
  65
  66 /*
  67  * Wrapper for usb_control_msg().
  68  * Allocates a temp buffer to prevent dmaing from/to the stack.
  69  */
  70 int snd_usb_ctl_msg(struct usb_device *dev, unsigned int pipe, __u8 request,
  71                     __u8 requesttype, __u16 value, __u16 index, void *data,
  72                     __u16 size)
  73 {
  74         int err;
  75         void *buf = NULL;
  76         int timeout;
  77
  78         if (size > 0) {
  79                 buf = kmemdup(data, size, GFP_KERNEL);
  80                 if (!buf)
  81                         return -ENOMEM;
  82         }
  83
  84         if (requesttype & USB_DIR_IN)
  85                 timeout = USB_CTRL_GET_TIMEOUT;
  86         else
  87                 timeout = USB_CTRL_SET_TIMEOUT;
  88
  89         err = usb_control_msg(dev, pipe, request, requesttype,
  90                               value, index, buf, size, timeout);
  91
  92         if (size > 0) {
  93                 memcpy(data, buf, size);
  94                 kfree(buf);
  95         }
  96
  97         snd_usb_ctl_msg_quirk(dev, pipe, request, requesttype,
  98                               value, index, data, size);
  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_WIRELESS:
 109         case USB_SPEED_SUPER:
 110         case USB_SPEED_SUPER_PLUS:
 111                 if (get_endpoint(alts, 0)->bInterval >= 1 &&
 112                     get_endpoint(alts, 0)->bInterval <= 4)
 113                         return get_endpoint(alts, 0)->bInterval - 1;
 114                 break;
 115         default:
 116                 break;
 117         }
 118         return 0;
 119 }
 120