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>Chapter 8. Basic Examples</H1
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>Before any communication can occur with a device, it needs to be found. This is accomplished by finding all of the busses and then finding all of the devices on all of the busses:</P
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> struct usb_bus *busses;
usb_init();
usb_find_busses();
usb_find_devices();
busses = usb_get_busses();
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>After this, the application should manually loop through all of the busess and all of the devices and matching the device by whatever criteria is needed:</P
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> struct usb_bus *bus;
int c, i, a;
/* ... */
for (bus = busses; bus; bus = bus->next) {
struct usb_device *dev;
for (dev = bus->devices; dev; dev = dev->next) {
/* Check if this device is a printer */
if (dev->descriptor.bDeviceClass == 7) {
/* Open the device, claim the interface and do your processing */
...
}
/* Loop through all of the configurations */
for (c = 0; c < dev->descriptor.bNumConfigurations; c++) {
/* Loop through all of the interfaces */
for (i = 0; i < dev->config[c].bNumInterfaces; i++) {
/* Loop through all of the alternate settings */
for (a = 0; a < dev->config[c].interface[i].num_altsetting; a++) {
/* Check if this interface is a printer */
if (dev->config[c].interface[i].altsetting[a].bInterfaceClass == 7) {
/* Open the device, set the alternate setting, claim the interface and do your processing */
...
}
}
}
}
}
}
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