1 files changed, 113 insertions, 0 deletions

diff --git a/sound/usb/helper.c b/sound/usb/helper.c
new file mode 100644
index 000000000000..d48d6f8f6ac9
--- /dev/null
+++ b/sound/usb/helper.c
@@ -0,0 +1,113 @@
+/*
+ *   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)
+{
+        if (snd_usb_get_speed(chip->dev) == USB_SPEED_HIGH &&
+            get_endpoint(alts, 0)->bInterval >= 1 &&
+            get_endpoint(alts, 0)->bInterval <= 4)
+                return get_endpoint(alts, 0)->bInterval - 1;
+        else
+                return 0;
+}
+