usb: add support for "grouped" interfaces and the Interface Association Descriptor

This is used for some devices that have multiple interfaces that form a logic
device. An example is Video Class, which has a Control interface and a
Streaming interface. There can be additional interfaces on the same (physical)
devices (e.g. a microphone), and Interface Association Descriptor handles this
case.

Signed-off-by: Brad Hards <bradh@frogmouth.net>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

hw/usb-desc.c

@@ -91,6 +91,18 @@ int usb_desc_config(const USBDescConfig *conf, uint8_t *dest, size_t len)
     dest[0x08] = conf->bMaxPower;
     wTotalLength += bLength;
 
+    /* handle grouped interfaces if any*/
+    for (i = 0; i < conf->nif_groups; i++) {
+        rc = usb_desc_iface_group(&(conf->if_groups[i]),
+                                  dest + wTotalLength,
+                                  len - wTotalLength);
+        if (rc < 0) {
+            return rc;
+        }
+        wTotalLength += rc;
+    }
+
+    /* handle normal (ungrouped / no IAD) interfaces if any */
     for (i = 0; i < conf->nif; i++) {
         rc = usb_desc_iface(conf->ifs + i, dest + wTotalLength, len - wTotalLength);
         if (rc < 0) {
@@ -104,6 +116,41 @@ int usb_desc_config(const USBDescConfig *conf, uint8_t *dest, size_t len)
     return wTotalLength;
 }
 
+int usb_desc_iface_group(const USBDescIfaceAssoc *iad, uint8_t *dest,
+                         size_t len)
+{
+    int pos = 0;
+    int i = 0;
+
+    /* handle interface association descriptor */
+    uint8_t bLength = 0x08;
+
+    if (len < bLength) {
+        return -1;
+    }
+
+    dest[0x00] = bLength;
+    dest[0x01] = USB_DT_INTERFACE_ASSOC;
+    dest[0x02] = iad->bFirstInterface;
+    dest[0x03] = iad->bInterfaceCount;
+    dest[0x04] = iad->bFunctionClass;
+    dest[0x05] = iad->bFunctionSubClass;
+    dest[0x06] = iad->bFunctionProtocol;
+    dest[0x07] = iad->iFunction;
+    pos += bLength;
+
+    /* handle associated interfaces in this group */
+    for (i = 0; i < iad->nif; i++) {
+        int rc = usb_desc_iface(&(iad->ifs[i]), dest + pos, len - pos);
+        if (rc < 0) {
+            return rc;
+        }
+        pos += rc;
+    }
+
+    return pos;
+}
+
 int usb_desc_iface(const USBDescIface *iface, uint8_t *dest, size_t len)
 {
     uint8_t bLength = 0x09;

hw/usb-desc.h

@@ -30,6 +30,24 @@ struct USBDescConfig {
     uint8_t                   bmAttributes;
     uint8_t                   bMaxPower;
 
+    /* grouped interfaces */
+    uint8_t                   nif_groups;
+    const USBDescIfaceAssoc   *if_groups;
+
+    /* "normal" interfaces */
+    uint8_t                   nif;
+    const USBDescIface        *ifs;
+};
+
+/* conceptually an Interface Association Descriptor, and releated interfaces */
+struct USBDescIfaceAssoc {
+    uint8_t                   bFirstInterface;
+    uint8_t                   bInterfaceCount;
+    uint8_t                   bFunctionClass;
+    uint8_t                   bFunctionSubClass;
+    uint8_t                   bFunctionProtocol;
+    uint8_t                   iFunction;
+
     uint8_t                   nif;
     const USBDescIface        *ifs;
 };
@@ -75,6 +93,8 @@ int usb_desc_device(const USBDescID *id, const USBDescDevice *dev,
 int usb_desc_device_qualifier(const USBDescDevice *dev,
                               uint8_t *dest, size_t len);
 int usb_desc_config(const USBDescConfig *conf, uint8_t *dest, size_t len);
+int usb_desc_iface_group(const USBDescIfaceAssoc *iad, uint8_t *dest,
+                         size_t len);
 int usb_desc_iface(const USBDescIface *iface, uint8_t *dest, size_t len);
 int usb_desc_endpoint(const USBDescEndpoint *ep, uint8_t *dest, size_t len);
 int usb_desc_other(const USBDescOther *desc, uint8_t *dest, size_t len);

hw/usb.h

@@ -141,6 +141,7 @@ typedef struct USBDesc USBDesc;
 typedef struct USBDescID USBDescID;
 typedef struct USBDescDevice USBDescDevice;
 typedef struct USBDescConfig USBDescConfig;
+typedef struct USBDescIfaceAssoc USBDescIfaceAssoc;
 typedef struct USBDescIface USBDescIface;
 typedef struct USBDescEndpoint USBDescEndpoint;
 typedef struct USBDescOther USBDescOther;