am7xxx-modeswitch: add a blank line for readability

[libam7xxx.git] / examples / am7xxx-modeswitch.c

diff --git a/examples/am7xxx-modeswitch.c b/examples/am7xxx-modeswitch.c
index f719f03..2764ab2 100644 (file)
--- a/examples/am7xxx-modeswitch.c
+++ b/examples/am7xxx-modeswitch.c
@@ -17,6 +17,7 @@
  */
 
 #include <stdio.h>
+#include <string.h>
 #include <errno.h>
 #include <libusb.h>
 
@@ -33,14 +34,17 @@ static unsigned char switch_command[] =
 int main(void)
 {
        int ret;
-       int transferred;
-       libusb_device_handle *usb_device = NULL;
-
+       libusb_device_handle *usb_device;
+       int current_configuration;
        unsigned int len;
+       int transferred;
 
        ret = libusb_init(NULL);
-       if (ret < 0)
+       if (ret < 0) {
+               fprintf(stderr, "libusb_init failed: %s\n",
+                       libusb_error_name(ret));
                goto out;
+       }
 
        libusb_set_debug(NULL, LIBUSB_LOG_LEVEL_INFO);
 
@@ -48,26 +52,62 @@ int main(void)
                                                     AM7XXX_STORAGE_VID,
                                                     AM7XXX_STORAGE_PID);
        if (usb_device == NULL) {
-               fprintf(stderr, "cannot open the device: %d.\n", errno);
+               fprintf(stderr, "libusb_open failed: %s\n", strerror(errno));
                ret = -errno;
                goto out;
        }
 
-       ret = libusb_set_configuration(usb_device, AM7XXX_STORAGE_CONFIGURATION);
+       current_configuration = -1;
+       ret = libusb_get_configuration(usb_device, &current_configuration);
        if (ret < 0) {
-               fprintf(stderr, "cannot set configuration.\n");
+               fprintf(stderr, "libusb_get_configuration failed: %s\n",
+                       libusb_error_name(ret));
                goto out_libusb_close;
        }
 
+       if (current_configuration != AM7XXX_STORAGE_CONFIGURATION) {
+               ret = libusb_set_configuration(usb_device,
+                                              AM7XXX_STORAGE_CONFIGURATION);
+               if (ret < 0) {
+                       fprintf(stderr, "libusb_set_configuration failed: %s\n",
+                               libusb_error_name(ret));
+                       fprintf(stderr, "Cannot set configuration %hhu\n",
+                               AM7XXX_STORAGE_CONFIGURATION);
+                       goto out_libusb_close;
+               }
+       }
+
        libusb_set_auto_detach_kernel_driver(usb_device, 1);
 
        ret = libusb_claim_interface(usb_device, AM7XXX_STORAGE_INTERFACE);
        if (ret < 0) {
-               fprintf(stderr, "cannot claim interface.\n");
+               fprintf(stderr, "libusb_claim_interface failed: %s\n",
+                       libusb_error_name(ret));
+               fprintf(stderr, "Cannot claim interface %hhu\n",
+                       AM7XXX_STORAGE_INTERFACE);
                goto out_libusb_close;
        }
 
+       /* Checking that the configuration has not changed, as suggested in
+        * http://libusb.sourceforge.net/api-1.0/caveats.html
+        */
+       current_configuration = -1;
+       ret = libusb_get_configuration(usb_device, &current_configuration);
+       if (ret < 0) {
+               fprintf(stderr, "libusb_get_configuration after claim failed: %s\n",
+                       libusb_error_name(ret));
+               goto out_libusb_release_interface;
+       }
+
+       if (current_configuration != AM7XXX_STORAGE_CONFIGURATION) {
+               fprintf(stderr, "libusb configuration changed (expected: %hhu, current: %hhu\n",
+                       AM7XXX_STORAGE_CONFIGURATION, current_configuration);
+               ret = -EINVAL;
+               goto out_libusb_release_interface;
+       }
+
        len = sizeof(switch_command);
+
        transferred = 0;
        ret = libusb_bulk_transfer(usb_device, AM7XXX_STORAGE_OUT_EP,
                                   switch_command, len, &transferred, 0);