[PATCH v2] usb: gadget: f_uac1: add interface association descriptor

[Chunfeng Yun <chunfeng.yun@mediatek.com>]

From: xin lin <xin.lin@mediatek.com>

When we want to use a composite device that supports UVC, UAC1 and
ADB at the same time, encounter that UAC1 can't work when connected
to windows 10 system.
From the online documents of microsoft, "overview of enumeration of
interface collections on usb composite devices", it recommends that
vendors use IADs (interface association descriptor) to define
interface collections.
After addding IAD, we can fix the issue.

Signed-off-by: xin lin <xin.lin@mediatek.com>
Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
---
v2: modify commit log suggested by Greg
---
 drivers/usb/gadget/function/f_uac1.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/drivers/usb/gadget/function/f_uac1.c b/drivers/usb/gadget/function/f_uac1.c
index 6f0e1d803dc2..8390207bc513 100644
--- a/drivers/usb/gadget/function/f_uac1.c
+++ b/drivers/usb/gadget/function/f_uac1.c
@@ -71,6 +71,17 @@ static inline struct f_uac1_opts *g_audio_to_uac1_opts(struct g_audio *audio)
  * ALSA_Playback -> IT_3 -> OT_4 -> USB-IN
  */
 
+static struct usb_interface_assoc_descriptor iad_desc = {
+	.bLength = sizeof(iad_desc),
+	.bDescriptorType = USB_DT_INTERFACE_ASSOCIATION,
+
+	.bFirstInterface = 0,
+	.bInterfaceCount = 3,
+	.bFunctionClass = USB_CLASS_AUDIO,
+	.bFunctionSubClass = 0,
+	.bFunctionProtocol = UAC_VERSION_1,
+};
+
 /* B.3.1  Standard AC Interface Descriptor */
 static struct usb_interface_descriptor ac_interface_desc = {
 	.bLength =		USB_DT_INTERFACE_SIZE,
@@ -259,6 +270,7 @@ static struct uac_iso_endpoint_descriptor as_iso_in_desc = {
 };
 
 static struct usb_descriptor_header *f_audio_desc[] = {
+	(struct usb_descriptor_header *)&iad_desc,
 	(struct usb_descriptor_header *)&ac_interface_desc,
 	(struct usb_descriptor_header *)&ac_header_desc,
 
@@ -293,6 +305,7 @@ static struct usb_descriptor_header *f_audio_desc[] = {
 };
 
 enum {
+	STR_ASSOC,
 	STR_AC_IF,
 	STR_USB_OUT_IT,
 	STR_USB_OUT_IT_CH_NAMES,
@@ -310,6 +323,7 @@ enum {
 
 static struct usb_string strings_uac1[] = {
 	/* [STR_AC_IF].s = DYNAMIC, */
+	[STR_ASSOC].s = "Source/Sink",
 	[STR_USB_OUT_IT].s = "Playback Input terminal",
 	[STR_USB_OUT_IT_CH_NAMES].s = "Playback Channels",
 	[STR_IO_OUT_OT].s = "Playback Output terminal",
@@ -1058,6 +1072,7 @@ static void setup_descriptor(struct f_uac1_opts *opts)
 	as_out_header_desc.bTerminalLink = usb_out_it_desc.bTerminalID;
 	as_in_header_desc.bTerminalLink = usb_in_ot_desc.bTerminalID;
 
+	iad_desc.bInterfaceCount = 1;
 	ac_header_desc->wTotalLength = cpu_to_le16(ac_header_desc->bLength);
 
 	if (EPIN_EN(opts)) {
@@ -1068,6 +1083,7 @@ static void setup_descriptor(struct f_uac1_opts *opts)
 		if (FUIN_EN(opts))
 			len += in_feature_unit_desc->bLength;
 		ac_header_desc->wTotalLength = cpu_to_le16(len);
+		iad_desc.bInterfaceCount++;
 	}
 	if (EPOUT_EN(opts)) {
 		u16 len = le16_to_cpu(ac_header_desc->wTotalLength);
@@ -1077,9 +1093,11 @@ static void setup_descriptor(struct f_uac1_opts *opts)
 		if (FUOUT_EN(opts))
 			len += out_feature_unit_desc->bLength;
 		ac_header_desc->wTotalLength = cpu_to_le16(len);
+		iad_desc.bInterfaceCount++;
 	}
 
 	i = 0;
+	f_audio_desc[i++] = USBDHDR(&iad_desc);
 	f_audio_desc[i++] = USBDHDR(&ac_interface_desc);
 	f_audio_desc[i++] = USBDHDR(ac_header_desc);
 
@@ -1217,6 +1235,7 @@ static int f_audio_bind(struct usb_configuration *c, struct usb_function *f)
 		}
 	}
 
+	iad_desc.iFunction = us[STR_ASSOC].id;
 	ac_interface_desc.iInterface = us[STR_AC_IF].id;
 	usb_out_it_desc.iTerminal = us[STR_USB_OUT_IT].id;
 	usb_out_it_desc.iChannelNames = us[STR_USB_OUT_IT_CH_NAMES].id;
@@ -1302,6 +1321,8 @@ static int f_audio_bind(struct usb_configuration *c, struct usb_function *f)
 	status = usb_interface_id(c, f);
 	if (status < 0)
 		goto err_free_fu;
+
+	iad_desc.bFirstInterface = status;
 	ac_interface_desc.bInterfaceNumber = status;
 	uac1->ac_intf = status;
 	uac1->ac_alt = 0;
-- 
2.18.0