Drivers Libusb.org Others

Introduction
We often come across a situation where a USB device which runs perfectly on Windows platform does not even get detected on Linux. Lack of support for USB devices is one of the reason why some people don't embrace Linux. Now there is a new API by name Libusb which helps the developers to develop USB device drivers on the fly!
What is Libusb
Libusb is a high-level language API which conceals low-level kernel interactions with the USB modules. It provides a set of function which are adequate to develop a device driver for a USB device from the Userspace.
Libusb is not complex
For any wannabe Linux Kernel programmers developing device driver as a Kernel module is a herculean task. Developing kernel modules requires fair degree of proficiency in 'C' language and also good idea of kernel subsystems, data structures etc. All these are enough to put-off a developer from venturing into Device Driver programming.Libusb has been designed to address this shortcoming. Simplified interface allows developers to develop USB drivers from the userspace . Libusb library functions provide high level abstraction to the Kernel structures and allows the developers to have access to these structures through the USBFS(USBfilesystem).
Its Cross-platform
Beauty of Libusb lies in its cross platform functionality. Driver written for one platform could be easily ported onto another platform with little or no changes, currently following operating systems are supported by Libusb.
Linux
FreeBSD
Darwin
OS X
This HOWTO focuses on how Libusb can be used on Linux platform. For information about other platforms goto http://http://libusb.sourceforge.net/.
LIBUSB ON LINUX
Linux is the most popular platform for the Libusb API,the reason being growing popularity of Linux as a stable OS. On Linux Libusb makes of the USBFS file system. by default USBFS is automatically mounted when the system is booted.
What is USBFS
USBFS is a filesystem specifically designed for USB devices, by default this filesystem gets mounted when the system is booted and it can be found at /proc/bus/usb/. This filesystem consists of information about all the USB devices that are connected to the computer.Libusb makes use of this filesystem to interact with the USB devices.
Following C program can be a stepping stone into the world of Libusb.This program can be used to gather all the technical/hardware details of a USB device connected to the computer ,ensure that some USB device is connected into the USB port.
Details like Vendor-Id , Product-Id ,Endpoint addresses of a USB device is of paramount importance for a device driver developer.
/* testlibusb.c */
#include
#include
void print_endpoint(struct usb_endpoint_descriptor *endpoint)
{
printf(' bEndpointAddress: %02xhn', endpoint->bEndpointAddress);
printf(' bmAttributes: %02xhn', endpoint->bmAttributes);
printf(' wMaxPacketSize: %dn', endpoint->wMaxPacketSize);
printf(' bInterval: %dn', endpoint->bInterval);
printf(' bRefresh: %dn', endpoint->bRefresh);
printf(' bSynchAddress: %dn', endpoint->bSynchAddress);
}
void print_altsetting(struct usb_interface_descriptor *interface)
{
int i;
printf(' bInterfaceNumber: %dn', interface->bInterfaceNumber);
printf(' bAlternateSetting: %dn', interface->bAlternateSetting);
printf(' bNumEndpoints: %dn', interface->bNumEndpoints);
printf(' bInterfaceClass: %dn', interface->bInterfaceClass);
printf(' bInterfaceSubClass: %dn', interface->bInterfaceSubClass);
printf(' bInterfaceProtocol: %dn', interface->bInterfaceProtocol);
printf(' iInterface: %dn', interface->iInterface);
for (i = 0; i < interface->bNumEndpoints; i++)
print_endpoint(&interface->endpoint[i]);
}
void print_interface(struct usb_interface *interface)
{
int i;
for (i = 0; i < interface->num_altsetting; i++)
print_altsetting(&interface->altsetting[i]);
}
void print_configuration(struct usb_config_descriptor *config)
{
int i;
printf(' wTotalLength: %dn', config->wTotalLength);
printf(' bNumInterfaces: %dn', config->bNumInterfaces);
printf(' bConfigurationValue: %dn', config->bConfigurationValue);
printf(' iConfiguration: %dn', config->iConfiguration);
printf(' bmAttributes: %02xhn', config->bmAttributes);
printf(' MaxPower: %dn', config->MaxPower);
for (i = 0; i < config->bNumInterfaces; i++)
print_interface(&config->interface[i]);
}
int main(void)
{
struct usb_bus *bus;
struct usb_device *dev;
usb_init();
usb_find_busses();
usb_find_devices();
printf('bus/device idVendor/idProductn');
for (bus = usb_busses; bus; bus = bus->next) {
for (dev = bus->devices; dev; dev = dev->next) {
int ret, i;
char string[256];
usb_dev_handle *udev;
printf('%s/%s %04X/%04Xn', bus->dirname, dev->filename,
dev->descriptor.idVendor, dev->descriptor.idProduct);
udev = usb_open(dev);
if (udev) {
if (dev->descriptor.iManufacturer) {
ret = usb_get_string_simple(udev, dev->descriptor.iManufacturer, string, sizeof(string));
if (ret > 0)
printf('- Manufacturer : %sn', string);
else
printf('- Unable to fetch manufacturer stringn');
}
if (dev->descriptor.iProduct) {
ret = usb_get_string_simple(udev, dev->descriptor.iProduct, string, sizeof(string));
if (ret > 0)
printf('- Product : %sn', string);
else
printf('- Unable to fetch product stringn');
}
if (dev->descriptor.iSerialNumber) {
ret = usb_get_string_simple(udev, dev->descriptor.iSerialNumber, string, sizeof(string));
if (ret > 0)
printf('- Serial Number: %sn', string);
else
printf('- Unable to fetch serial number stringn');
}
usb_close (udev);
}
if (!dev->config) {
printf(' Couldn't retrieve descriptorsn');
continue;
}
for (i = 0; i < dev->descriptor.bNumConfigurations; i++)
print_configuration(&dev->config[i]);
}
}
return 0;
}
The above program should be compiled as
(root$)gcc -o usbdevice_details testlibusb.c -I/usr/local/include -L. -lnsl -lm -lc -L/usr/local/lib -lusb
(root$)./usbdevice_details (enter)
Following is the output of the above command ,its the listing of a USB pen drive connected to my system.
The first line displays the bus-name/device-name & device-id/product-id and rest of the listing is self-descriptive.
001/004 0EA0/2168
- Manufacturer : USB
- Product : Flash Disk
- Serial Number: 4CE45C4E403EE53D
wTotalLength: 39
bNumInterfaces: 1
bConfigurationValue: 1
iConfiguration: 0
bmAttributes: 80h
MaxPower: 100
bInterfaceNumber: 0
bAlternateSetting: 0
bNumEndpoints: 3
bInterfaceClass: 8
bInterfaceSubClass: 6
bInterfaceProtocol: 80
iInterface: 0
bEndpointAddress: 81h
bmAttributes: 02h
wMaxPacketSize: 64
bInterval: 0
bRefresh: 0
bSynchAddress: 0
bEndpointAddress: 02h
bmAttributes: 02h
wMaxPacketSize: 64
bInterval: 0
bRefresh: 0
bSynchAddress: 0
bEndpointAddress: 83h
bmAttributes: 03h
wMaxPacketSize: 2
bInterval: 1
bRefresh: 0
bSynchAddress: 0
Before executing the above program download the current version of Libusb library from, http://http://libusb.sourceforge.net/. The above program can also be found under the tests directory of Libusb directory (after u install it)
Now I will explain in brief some of the functions and attributes dealt in the above program.
usb_init() - Used to initialize Libusb and establish connection with kernel structures .
usb_find_busses() - Looks for all the USB busses on the computer.
usb_find_devices() - Looks for all the USB devices connected to the computer.
usb_open(dev) - Opens the device 'dev' which is given as argument to this function.
usb_get_string_simple() - Used to extract the string descriptor of the device taken argument.
Important attributes of USB devices useful in device driver coding
Configuration and Endpoints are one of the two important descriptors of any USB device. These descriptors are defined using the

Drivers Libusb.org Others Help
Drivers Libusb.org Others And Others
Drivers Libusb.org Others Crossword Clue

const struct libusb_version *libusb_get_version(void)This function returns version information about LibUSB.

intlibusb_init(libusb_context **ctx)This function initialises libusb.It must be called at the beginningof the program, before other libusb routines are used.This function returns 0 on success or LIBUSB_ERROR onfailure.

The zadib driver should match the backend driver should both be libusb-win32, so far no luck with other drivers/backends Solution download libusb-win32 sources. Libusb will be unable to set a configuration if other programs or drivers have claimed interfaces. In particular, this means that kernel drivers must be detached from all the interfaces before libusbsetconfiguration may succeed. One solution to some of the above problems is to consider the currently active configuration.

voidlibusb_exit(libusb_context *ctx)Deinitialise libusb.Must be called at the end of the application.Other libusb routines may not be called after this function.

intlibusb_has_capability(uint32_t capability)This function checks the runtime capabilities of

libusb.This function will return non-zero if the givencapability

Drivers Libusb.org Others Help

is supported, 0 if it is not supported.The valid values for Drivers libusb.org others and others

capability Libusb.org

are:

LIBUSB_CAP_HAS_CAPABILITY
libusbsupports`libusb_has_capability()`.
LIBUSB_CAP_HAS_HOTPLUG
libusbsupports hotplug notifications.
LIBUSB_CAP_HAS_HID_ACCESS
libusbcan access HID devices without requiring user intervention.
LIBUSB_CAP_SUPPORTS_DETACH_KERNEL_DRIVER
libusbsupports detaching of the default USB driver with`libusb_detach_kernel_driver()`.

const char *libusb_strerror(int code)Get the ASCII representation of the error given by thecodeargument.This function does not return NULL.

const char *libusb_error_name(int code)Get the ASCII representation of the error enum given by thecodeargument.This function does not return NULL.

voidlibusb_set_debug(libusb_context *ctx, int level)Set the debug level tolevel.

ssize_tlibusb_get_device_list(libusb_context *ctx, libusb_device ***list)Populatelistwith the list of usb devices available, adding a reference to eachdevice in the list.All the list entries created by thisfunction must have their reference counterdecremented when you are done with them,and the list itself must be freed.Thisfunction returns the number of devices in the list or a LIBUSB_ERROR code.

voidlibusb_free_device_list(libusb_device **list, int unref_devices)Free the list of devices discovered by libusb_get_device_list.Ifunref_deviceis set to 1 all devices in the list have their referencecounter decremented once.

uint8_tlibusb_get_bus_number(libusb_device *dev)Returns the number of the bus contained by the devicedev.

uint8_tlibusb_get_port_number(libusb_device *dev)Returns the port number which the device given bydevis attached to.

intlibusb_get_port_numbers(libusb_device *dev, uint8_t *buf, uint8_t bufsize)Stores, in the bufferbufof sizebufsize,the list of all port numbers from root for the devicedev.

intlibusb_get_port_path(libusb_context *ctx, libusb_device *dev, uint8_t *buf, uint8_t bufsize)Deprecated function equivalent to libusb_get_port_numbers.

uint8_tlibusb_get_device_address(libusb_device *dev)Returns the device_address contained by the devicedev.

enum libusb_speedlibusb_get_device_speed(libusb_device *dev)Returns the wire speed at which the device is connected.See the LIBUSB_SPEED_XXX enums for more information.LIBUSB_SPEED_UNKNOWN is returned in case of unknown wire speed.

intlibusb_get_max_packet_size(libusb_device *dev, unsigned char endpoint)Returns the wMaxPacketSize value on success, LIBUSB_ERROR_NOT_FOUND if theendpoint does not exist and LIBUSB_ERROR_OTHERS on other failure.

intlibusb_get_max_iso_packet_size(libusb_device *dev, unsigned char endpoint)Returns the packet size multiplied by the packet multiplier on success,LIBUSB_ERROR_NOT_FOUND if the endpoint does not exist andLIBUSB_ERROR_OTHERS on other failure.

libusb_device *libusb_ref_device(libusb_device *dev)Increment the reference counter of the devicedev.

Drivers Libusb.org Others And Others

voidlibusb_unref_device(libusb_device *dev)Decrement the reference counter of the devicedev.

intlibusb_open(libusb_device *dev, libusb_device_handle **devh)Open a device and obtain a device_handle.Returns 0 on success,LIBUSB_ERROR_NO_MEM on memory allocation problems, LIBUSB_ERROR_ACCESSon permissions problems, LIBUSB_ERROR_NO_DEVICE if the device has beendisconnected and a LIBUSB_ERROR code on other errors.

libusb_device_handle *libusb_open_device_with_vid_pid(libusb_context *ctx, uint16_t vid, uint16_t pid)A convenience function to open a device by vendor and product IDsvidandpid.Returns NULL on error.

voidlibusb_close(libusb_device_handle *devh)Close a device handle.

libusb_device *libusb_get_device(libusb_device_handle *devh)Get the device contained by devh.Returns NULL on error.

intlibusb_get_configuration(libusb_device_handle *devh, int *config)Returns the value of the current configuration.Returns 0on success, LIBUSB_ERROR_NO_DEVICE if the device has been disconnectedand a LIBUSB_ERROR code on error.

intlibusb_set_configuration(libusb_device_handle *devh, int config)Set the active configuration toconfigfor the device contained bydevh.This function returns 0 on success, LIBUSB_ERROR_NOT_FOUND if the requestedconfiguration does not exist, LIBUSB_ERROR_BUSY if the interfaces are currentlyclaimed, LIBUSB_ERROR_NO_DEVICE if the device has been disconnected and aLIBUSB_ERROR code on failure.

intlibusb_claim_interface(libusb_device_handle *devh, int interface_number)Claim an interface in a given libusb_handledevh.This is a non-blocking function.It returns 0 on success, LIBUSB_ERROR_NOT_FOUNDif the requested interface does not exist, LIBUSB_ERROR_BUSY if a program ordriver has claimed the interface, LIBUSB_ERROR_NO_DEVICE if the device hasbeen disconnected and a LIBUSB_ERROR code on failure.

intlibusb_release_interface(libusb_device_handle *devh, int interface_number)This function releases an interface.All the claimed interfaces on a device must be releasedbefore closing the device.Returns 0 on success, LIBUSB_ERROR_NOT_FOUND if theinterface was not claimed, LIBUSB_ERROR_NO_DEVICE if the device has beendisconnected and LIBUSB_ERROR on failure.

intlibusb_set_interface_alt_setting(libusb_device_handle *dev, int interface_number, int alternate_setting)Activate an alternate setting for an interface.Returns 0 on success,LIBUSB_ERROR_NOT_FOUND if the interface was not claimed or the requestedsetting does not exist, LIBUSB_ERROR_NO_DEVICE if the device has beendisconnected and a LIBUSB_ERROR code on failure.

intlibusb_clear_halt(libusb_device_handle *devh, unsigned char endpoint)Clear an halt/stall for a endpoint.Returns 0 on success, LIBUSB_ERROR_NOT_FOUNDif the endpoint does not exist, LIBUSB_ERROR_NO_DEVICE if the device has beendisconnected and a LIBUSB_ERROR code on failure.

intlibusb_reset_device(libusb_device_handle *devh)Perform an USB port reset for an usb device.Returns 0 on success,LIBUSB_ERROR_NOT_FOUND if re-enumeration is required or if the device hasbeen disconnected and a LIBUSB_ERROR code on failure.

intlibusb_check_connected(libusb_device_handle *devh)Test if the USB device is still connected.Returns 0 on success,LIBUSB_ERROR_NO_DEVICE if it has been disconnected and a LIBUSB_ERRORcode on failure.

intlibusb_kernel_driver_active(libusb_device_handle *devh, int interface)Determine if a driver is active on a interface.Returns 0 if no kernel driver is activeand 1 if a kernel driver is active, LIBUSB_ERROR_NO_DEVICEif the device has been disconnected and a LIBUSB_ERROR code on failure.

Drivers Libusb.org Others Crossword Clue

intlibusb_get_driver(libusb_device_handle *devh, int interface, char *name, int namelen)or intlibusb_get_driver_np(libusb_device_handle *devh, int interface, char *name, int namelen)Copy the name of the driver attached to the givendeviceandinterfaceinto the buffernameof lengthnamelen.Returns 0 on success, LIBUSB_ERROR_NOT_FOUND if no kernel driver is attachedto the given interface and LIBUSB_ERROR_INVALID_PARAM if the interface doesnot exist.This function is non-portable.The buffer pointed to bynameis only zero terminated on success.

intlibusb_detach_kernel_driver(libusb_device_handle *devh, int interface)or intlibusb_detach_kernel_driver_np(libusb_device_handle *devh, int interface)Detach a kernel driver from an interface.This is needed to claim an interface already claimed by a kernel driver.Returns 0 on success, LIBUSB_ERROR_NOT_FOUND if no kernel driver was active,LIBUSB_ERROR_INVALID_PARAM if the interface does not exist,LIBUSB_ERROR_NO_DEVICE if the device has been disconnectedand a LIBUSB_ERROR code on failure.This function is non-portable.

intlibusb_attach_kernel_driver(libusb_device_handle *devh, int interface)Re-attach an interface kernel driver that was previously detached.Returns 0 on success,LIBUSB_ERROR_INVALID_PARAM if the interface does not exist,LIBUSB_ERROR_NO_DEVICEif the device has been disconnected, LIBUSB_ERROR_BUSY if the driver cannot beattached because the interface is claimed by a program or driver and aLIBUSB_ERROR code on failure.

intlibusb_set_auto_detach_kernel_driver(libusb_device_handle *devh, int enable)This function enables automatic kernel interface driver detach when aninterface is claimed.When the interface is restored the kernel driver is allowed to be re-attached.If theenableargument is non-zero the feature is enabled.Else disabled.Returns 0 on success and a LIBUSB_ERROR code onfailure.