libusbhost: Add usb_device_set_configuration and usb_device_set_interface

usb_device_set_configuration is to support devices with multiple configurations
usb_device_set_interface supports switching between interfaces with alternate settings

Also moved zero string index checking to usb_device_get_string

Change-Id: I34610b25f135894a0cf752a33e5738d4314d7122

1 files changed, 20 insertions, 15 deletions

diff --git a/libusbhost/usbhost.c b/libusbhost/usbhost.c
index 8be393e..ab1b856 100644
--- a/libusbhost/usbhost.c
+++ b/libusbhost/usbhost.c
@@ -453,6 +453,8 @@ char* usb_device_get_string(struct usb_device *device, int id)
     int i, result;
     int languageCount = 0;
 
+    if (id == 0) return NULL;
+
     string[0] = 0;
     memset(languages, 0, sizeof(languages));
 
@@ -486,31 +488,19 @@ char* usb_device_get_string(struct usb_device *device, int id)
 char* usb_device_get_manufacturer_name(struct usb_device *device)
 {
     struct usb_device_descriptor *desc = (struct usb_device_descriptor *)device->desc;
-
-    if (desc->iManufacturer)
-        return usb_device_get_string(device, desc->iManufacturer);
-    else
-        return NULL;
+    return usb_device_get_string(device, desc->iManufacturer);
 }
 
 char* usb_device_get_product_name(struct usb_device *device)
 {
     struct usb_device_descriptor *desc = (struct usb_device_descriptor *)device->desc;
-
-    if (desc->iProduct)
-        return usb_device_get_string(device, desc->iProduct);
-    else
-        return NULL;
+    return usb_device_get_string(device, desc->iProduct);
 }
 
 char* usb_device_get_serial(struct usb_device *device)
 {
     struct usb_device_descriptor *desc = (struct usb_device_descriptor *)device->desc;
-
-    if (desc->iSerialNumber)
-        return usb_device_get_string(device, desc->iSerialNumber);
-    else
-        return NULL;
+    return usb_device_get_string(device, desc->iSerialNumber);
 }
 
 int usb_device_is_writeable(struct usb_device *device)
@@ -556,6 +546,21 @@ int usb_device_connect_kernel_driver(struct usb_device *device,
     return ioctl(device->fd, USBDEVFS_IOCTL, &ctl);
 }
 
+int usb_device_set_configuration(struct usb_device *device, int configuration)
+{
+    return ioctl(device->fd, USBDEVFS_SETCONFIGURATION, &configuration);
+}
+
+int usb_device_set_interface(struct usb_device *device, unsigned int interface,
+                            unsigned int alt_setting)
+{
+    struct usbdevfs_setinterface ctl;
+
+    ctl.interface = interface;
+    ctl.altsetting = alt_setting;
+    return ioctl(device->fd, USBDEVFS_SETINTERFACE, &ctl);
+}
+
 int usb_device_control_transfer(struct usb_device *device,
                             int requestType,
                             int request,