1 files changed, 133 insertions, 0 deletions
diff --git a/sound/usb/helper.c b/sound/usb/helper.c
new file mode 100644
index 000000000..a4410267b
--- /dev/null
+++ b/sound/usb/helper.c
@@ -0,0 +1,133 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ */
+
+#include <linux/init.h>
+#include <linux/slab.h>
+#include <linux/usb.h>
+
+#include "usbaudio.h"
+#include "helper.h"
+#include "quirks.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 err;
+	void *buf = NULL;
+	int timeout;
+
+	if (usb_pipe_type_check(dev, pipe))
+		return -EINVAL;
+
+	if (size > 0) {
+		buf = kmemdup(data, size, GFP_KERNEL);
+		if (!buf)
+			return -ENOMEM;
+	}
+
+	if (requesttype & USB_DIR_IN)
+		timeout = USB_CTRL_GET_TIMEOUT;
+	else
+		timeout = USB_CTRL_SET_TIMEOUT;
+
+	err = usb_control_msg(dev, pipe, request, requesttype,
+			      value, index, buf, size, timeout);
+
+	if (size > 0) {
+		memcpy(data, buf, size);
+		kfree(buf);
+	}
+
+	snd_usb_ctl_msg_quirk(dev, pipe, request, requesttype,
+			      value, index, data, size);
+
+	return err;
+}
+
+unsigned char snd_usb_parse_datainterval(struct snd_usb_audio *chip,
+					 struct usb_host_interface *alts)
+{
+	switch (snd_usb_get_speed(chip->dev)) {
+	case USB_SPEED_HIGH:
+	case USB_SPEED_WIRELESS:
+	case USB_SPEED_SUPER:
+	case USB_SPEED_SUPER_PLUS:
+		if (get_endpoint(alts, 0)->bInterval >= 1 &&
+		    get_endpoint(alts, 0)->bInterval <= 4)
+			return get_endpoint(alts, 0)->bInterval - 1;
+		break;
+	default:
+		break;
+	}
+	return 0;
+}
+
+struct usb_host_interface *
+snd_usb_get_host_interface(struct snd_usb_audio *chip, int ifnum, int altsetting)
+{
+	struct usb_interface *iface;
+
+	iface = usb_ifnum_to_if(chip->dev, ifnum);
+	if (!iface)
+		return NULL;
+	return usb_altnum_to_altsetting(iface, altsetting);
+}