DISCUSSION: Developing Linux Device Drivers using Libusb API
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This is a good article, but #include <...> are left out, and the indentation on the code is horrible (because there isn't any). I'm not sure if this is problem with the linuxanswers themselves, but it would look much better if it was properly formatted.
So (according to the preview button) you lose your indentation but I have no idea what happened to the #include directives in this post. Perhaps the author could fix it up with some 'code' tags. The ref to the sourceforge site also needs changing so it comes out as a link.
I've been searching for documentation on USB device drivers recently. There are a few good references but overall the situation is not very satisfactory. So almost anything is a positive contribution. If I understand correctly libusb lets you access USB devices even if they don't have kernel-level drivers. As the author suggests the (again rather brief) documentation at http://libusb.sourceforge.net/doc is worth a look for further code and examples. Apparently gphoto and rio500 are based on libusb.
I do not know if all of those are necessary. After compiling and testing I noticed that usb_get_string_simple does not return any string via string parameter when testing the program as a user. The return value of the function usb_get_string_simple is -1 all the time.
But when I changed to root user and tested the program, everything worked fine.
Anyway, I wonder if this phenomen has something to do with udev? With two different live-cd (gentoo and SuSE) boot process stopped just after udev:
...
Starting udev....
... udev running.
Starting hardware detection...
Activating usb devices... <-- boot stops here
(the above example is with the SuSE 10.1 installation CD-ROM and repair system option).
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 desciptors are defined using the “struct usb_config_descriptor” and “struct_usb_endpoint_descriptor” respectively .
dev->descriptor.idVendor : Reveals the Vendor-Id of the USB device connected to the system.
dev->descriptor.idProduct : Reveals the Product-Id of the USB device connected to the system.
dev->descriptor.iManufacturer : Reveals the name of the Manufacturer USB device connected to the system.
EndpointAddress:Combination of endpoint address and enpoint direction on a USB device.
InterfaceNumber : One of the several interfaces that is allocated to the connected USB device.
AlternateSetting:This is part of the a single interface allocated to the USB device.
Prerequites for Libusb programming
Linux system with Kernel 2.4 above series.
Proficiency in C language.
Good understanding of USB device internals.
Idea about USBFS.
Hi ppl, I used a similar test program to the one of the article.
Code:
/*
* testlibusb.c
*
* Test suite program
*/
#include <stdio.h>
#include <string.h>
#include "usb.h"
#define snprintf printf
#define ID_PRODUCT 0x0200
#define ID_VENDOR 0x8235
#define CONFIGURATION 1
#define INTERFACE_ 0
#define ALTINTERFACE 0
#define TIMEOUT 5000
#define OUT_ENDPOINT 0x01
#define IN_ENDPOINT 0x82
// #define SET_ALTINTERFACE_ONCE
int verbose = 0;
unsigned char first = true;
void print_endpoint(struct usb_endpoint_descriptor *endpoint)
{
printf(" bEndpointAddress: %02xh\n", endpoint->bEndpointAddress);
printf(" bmAttributes: %02xh\n", endpoint->bmAttributes);
printf(" wMaxPacketSize: %d\n", endpoint->wMaxPacketSize);
printf(" bInterval: %d\n", endpoint->bInterval);
printf(" bRefresh: %d\n", endpoint->bRefresh);
printf(" bSynchAddress: %d\n", endpoint->bSynchAddress);
}
void print_altsetting(struct usb_interface_descriptor *interface)
{
int i;
printf(" bInterfaceNumber: %d\n", interface->bInterfaceNumber);
printf(" bAlternateSetting: %d\n", interface->bAlternateSetting);
printf(" bNumEndpoints: %d\n", interface->bNumEndpoints);
printf(" bInterfaceClass: %d\n", interface->bInterfaceClass);
printf(" bInterfaceSubClass: %d\n", interface->bInterfaceSubClass);
printf(" bInterfaceProtocol: %d\n", interface->bInterfaceProtocol);
printf(" iInterface: %d\n", 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: %d\n", config->wTotalLength);
printf(" bNumInterfaces: %d\n", config->bNumInterfaces);
printf(" bConfigurationValue: %d\n", config->bConfigurationValue);
printf(" iConfiguration: %d\n", config->iConfiguration);
printf(" bmAttributes: %02xh\n", config->bmAttributes);
printf(" MaxPower: %d\n", config->MaxPower);
for (i = 0; i < config->bNumInterfaces; i++)
print_interface(&config->interface[i]);
}
int print_device(struct usb_device *dev, int level)
{
usb_dev_handle *udev;
char description[256];
char string[256];
int ret, i;
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)
snprintf(description, sizeof(description), "%s - ", string);
else
snprintf(description, sizeof(description), "%04X - ",
dev->descriptor.idVendor);
} else
snprintf(description, sizeof(description), "%04X - ",
dev->descriptor.idVendor);
if (dev->descriptor.iProduct) {
ret = usb_get_string_simple(udev, dev->descriptor.iProduct, string, sizeof(string));
if (ret > 0)
snprintf(description + strlen(description), sizeof(description) -
strlen(description), "%s", string);
else
snprintf(description + strlen(description), sizeof(description) -
strlen(description), "%04X", dev->descriptor.idProduct);
} else
snprintf(description + strlen(description), sizeof(description) -
strlen(description), "%04X", dev->descriptor.idProduct);
} else
snprintf(description, sizeof(description), "%04X - %04X",
dev->descriptor.idVendor, dev->descriptor.idProduct);
printf("%.*sDev #%d: %s\n", level * 2, " ", dev->devnum,
description);
if (udev && verbose) {
if (dev->descriptor.iSerialNumber) {
ret = usb_get_string_simple(udev, dev->descriptor.iSerialNumber, string, sizeof(string));
if (ret > 0)
printf("%.*s - Serial Number: %s\n", level * 2,
" ", string);
}
}
if (udev)
usb_close(udev);
if (verbose) {
if (!dev->config) {
printf(" Couldn't retrieve descriptors\n");
return 0;
}
for (i = 0; i < dev->descriptor.bNumConfigurations; i++)
print_configuration(&dev->config[i]);
} else {
for (i = 0; i < dev->num_children; i++)
print_device(dev->children[i], level + 1);
}
return 0;
}
int read(struct usb_dev_handle *handle)
{
if (usb_claim_interface(handle, INTERFACE_) < 0) {
printf("error on usb_claim_interface: %s\n", usb_strerror());
return -1;
}
printf("usb_claim_interface successful\n");
#ifdef SET_ALTINTERFACE_ONCE
if (first) {
first = false;
#endif
if (usb_set_altinterface(handle, ALTINTERFACE) < 0){
printf("usb_set_altinterface failed: %s\n", usb_strerror());
}
#ifdef SET_ALTINTERFACE_ONCE
}
#endif
int size = 512, res;
char *data = (char *) malloc(size*sizeof(char));
res = usb_bulk_read(handle, IN_ENDPOINT, data, size, TIMEOUT);
if (res < 0){
printf("usb_bulk_read failed: %s\n", usb_strerror());
}
printf("usb_bulk_read: %d bytes read: ", res);
for (int i = 0; i < res; ++i) {
printf("%3x ", data[i]);
}
printf("\n");
usb_release_interface(handle, INTERFACE_);
free(data);
}
int write(struct usb_dev_handle *handle)
{
int size = 12;
char *data = (char *) malloc(size*sizeof(char));
data[0] = 0x33;
data[1] = 0x5B;
data[2] = 0x02;
data[3] = 0x01;
data[4] = 0x00;
data[5] = 0x05;
data[6] = 0x01;
data[7] = 0x03;
data[8] = 0x07;
data[9] = 0x0F;
data[10] = 0x7F;
data[11] = 0x1F;
// data = {0x33, 0x5B, 0x02, 0x01, 0x00, 0x05, 0x01, 0x03, 0x07, 0x0F, 0x7F, 0x1F};
if (usb_claim_interface(handle, INTERFACE_) < 0) {
printf("error on usb_claim_interface: %s\n", usb_strerror());
return -1;
}
printf("usb_claim_interface successful\n");
#ifdef SET_ALTINTERFACE_ONCE
if (first) {
first = false;
#endif
if (usb_set_altinterface(handle, ALTINTERFACE) < 0){
printf("usb_set_altinterface failed: %s\n", usb_strerror());
}
#ifdef SET_ALTINTERFACE_ONCE
}
#endif
printf("usb_bulk_write: writing %d bytes: ", size);
for (int i = 0; i < size; ++i) {
printf("%3x ", data[i]);
}
printf("\n");
int res = usb_bulk_write(handle, OUT_ENDPOINT, data, size, TIMEOUT);
if (res < 0){
printf("usb_bulk_write failed: %s\n", usb_strerror());
return -1;
}
printf("usb_bulk_write: %d bytes written\n", res);
usb_release_interface(handle, INTERFACE_);
free(data);
}
int readWrite(struct usb_dev_handle *handle)
{
int size = 512;
char *data = (char *) malloc(size*sizeof(char));
printf("type a string...\n");
scanf("%s", data); // Get a string
if (usb_claim_interface(handle, INTERFACE_) < 0) {
printf("error on usb_claim_interface: %s\n", usb_strerror());
system("PAUSE");
return -1;
}
printf("usb_claim_interface successful\n");
#ifdef SET_ALTINTERFACE_ONCE
if (first) {
first = false;
#endif
if (usb_set_altinterface(handle, ALTINTERFACE) < 0){
printf("usb_set_altinterface failed: %s\n", usb_strerror());
}
#ifdef SET_ALTINTERFACE_ONCE
}
#endif
if (usb_bulk_write(handle, OUT_ENDPOINT, data, strlen(data), 3000) < 0){
printf("usb_bulk_write failed: %s\n", usb_strerror());
system("PAUSE");
return -1;
}
strcpy(data, "12345678901234567890");
printf("%s\n", "read data");
if (usb_bulk_read(handle, IN_ENDPOINT, data, size, 3000) < 0){
printf("usb_bulk_read failed: %s\n", usb_strerror());
}
printf("output %d, %s\n", size, data);
// for (int i = 0; i < size; ++i) {
// printf("%4x ", data[i]);
// }
usb_release_interface(handle, INTERFACE_);
free(data);
}
int readWriteLoop(struct usb_dev_handle *handle)
{
int NOF_LOOPS = 20;
int size = 12;
char *data = (char *) malloc(size*sizeof(char));
data[0] = 0x33;
data[1] = 0x5B;
data[2] = 0x02;
data[3] = 0x01;
data[4] = 0x00;
data[5] = 0x05;
data[6] = 0x01;
data[7] = 0x03;
data[8] = 0x07;
data[9] = 0x0F;
data[10] = 0x7F;
data[11] = 0x1F;
// data = {0x33, 0x5B, 0x02, 0x01, 0x00, 0x05, 0x01, 0x03, 0x07, 0x0F, 0x7F, 0x1F};
if (usb_claim_interface(handle, INTERFACE_) < 0) {
printf("error on usb_claim_interface: %s\n", usb_strerror());
return -1;
}
printf("usb_claim_interface successful\n");
#ifdef SET_ALTINTERFACE_ONCE
if (first) {
first = false;
#endif
if (usb_set_altinterface(handle, ALTINTERFACE) < 0){
printf("usb_set_altinterface failed: %s\n", usb_strerror());
}
#ifdef SET_ALTINTERFACE_ONCE
}
#endif
printf("usb_bulk_write: writing %d bytes: ", size);
for (int i = 0; i < size; ++i) {
printf("%3x ", data[i]);
}
printf("\n------------------------\n");
for (int var = 0; var < NOF_LOOPS; ++var) {
int res = usb_bulk_write(handle, OUT_ENDPOINT, data, size, TIMEOUT);
if (res < 0){
printf("usb_bulk_write failed: %s\n", usb_strerror());
return -1;
}
printf("usb_bulk_write: %d bytes written\n", res);
int size = 64;
char *data = (char *) malloc(size*sizeof(char));
res = usb_bulk_read(handle, IN_ENDPOINT, data, size, TIMEOUT);
if (res < 0){
printf("usb_bulk_read failed: %s\n", usb_strerror());
}
printf("usb_bulk_read: %d bytes read: ", res);
for (int i = 0; i < res; ++i) {
printf("%3x ", data[i]);
}
printf("\n");
}
usb_release_interface(handle, INTERFACE_);
free(data);
}
void logDevices()
{
struct usb_bus *bus;
printf("log devices...\n");
for (bus = usb_get_busses(); bus; bus = bus->next) {
if (bus->root_dev && !verbose)
print_device(bus->root_dev, 0);
else {
struct usb_device *dev;
for (dev = bus->devices; dev; dev = dev->next)
print_device(dev, 0);
}
}
}
int main(int argc, char *argv[])
{
struct usb_bus *bus;
struct usb_device *dev;
struct usb_dev_handle *handle;
bool run = true;
if (argc > 1 && !strcmp(argv[1], "-v"))
verbose = 1;
usb_set_debug(255);
printf("initialize libraray, find busses and devices\n");
usb_init();
usb_find_busses();
usb_find_devices();
if (verbose)
logDevices();
int size = 512;
char *data = (char *) malloc(size*sizeof(char));
printf("Search for device with idVendor 0x%x and idProduct 0x%x\n", ID_VENDOR, ID_PRODUCT);
for (bus = usb_get_busses(); bus; bus = bus->next) {
if (verbose)
printf("Found bus %s\n", bus->dirname);
for (dev = bus->devices; dev; dev = dev->next) {
if (verbose)
printf("Found device with idVendor 0x%x and idProduct 0x%x\n", dev->descriptor.idVendor, dev->descriptor.idProduct);
if ((dev->descriptor.idProduct == ID_PRODUCT) && (dev->descriptor.idVendor == ID_VENDOR)){
printf("Device found -> open\n");
handle = usb_open(dev);
if (!handle) {
printf("invalid handle: %s\n", usb_strerror());
system("PAUSE");
return -1;
}
printf("Set configuration\n");
if (usb_set_configuration(handle, CONFIGURATION) < 0) {
printf("error on usb_set_configuration: %s\n", usb_strerror());
system("PAUSE");
return -1;
}
printf("Set altinterface (must failed)\n");
#ifdef SET_ALTINTERFACE_ONCE
if (first) {
first = false;
#endif
if (usb_set_altinterface(handle, ALTINTERFACE) < 0){
printf("usb_set_altinterface failed: %s\n", usb_strerror());
}
#ifdef SET_ALTINTERFACE_ONCE
}
#endif
printf("w=write, r=read, x=exit, t=write+read, u=write+read(2), l=r/w loop, z=reset and open\n");
while (run) {
scanf("%s", data);
switch (data[0]) {
case 'w': // write
write(handle);
break;
case 'r': // read
read(handle);
break;
case 'x': // exit
run = false;
break;
case 't': // write + read
if (write(handle)) {
read(handle);
}
break;
case 'u': // write + read
readWrite(handle);
break;
case 'l': // loop
readWriteLoop(handle);
break;
case 's': // reset first flag (set_altinterface())
first = true;
break;
case 'z': // reset and open
usb_reset(handle);
handle = usb_open(dev);
break;
default:
break;
}
}
printf("\ndone\n");
}
}
}
free(data);
system("PAUSE");
return 1;
}
I executed it as root under Fedora core 5, I can list the usb buses but no the devices. The output is
Code:
usb_set_debug: Setting debugging level to 255 (on)
initialize libraray, find busses and devices
usb_os_init: Found USB VFS at /dev/bus/usb
usb_os_find_busses: Found 005
usb_os_find_busses: Found 004
usb_os_find_busses: Found 003
usb_os_find_busses: Found 002
usb_os_find_busses: Found 001
usb_os_find_busses: Skipping non bus directory devices
usb_os_find_devices: Found 004 on 005
skipped 1 class/vendor specific interface descriptors
usb_os_find_devices: Found 001 on 005
error obtaining child information: Inappropriate ioctl for device
usb_os_find_devices: Found 001 on 004
usb_os_find_devices: Found 001 on 003
usb_os_find_devices: Found 002 on 002
skipped 1 class/vendor specific interface descriptors
usb_os_find_devices: Found 001 on 002
error obtaining child information: Inappropriate ioctl for device
usb_os_find_devices: Found 001 on 001
log devices...
Search for device with idVendor 0x8235 and idProduct 0x200
Found bus 005
Found bus 004
Found bus 003
Found bus 002
Found bus 001
sh: PAUSE: command not found
Hi.
I wrote a shell-prog that communicates a selfmade USB-device using the libusb.
It works fine, but I only can use the prog if I am logged in as root. Every other user gets the message, that there is no device connected, but without changing anything root can control it.
I tried to "chmod 777" all the libusb-files in /usr/lib/, but that did not work, too.
Has anyone of you a clue, what the problem could be?
Thanks.
I tried to compile teslibusb.c:
gcc -o usbdevice_details testlibusb.c -I/usr/local/include -L. -lnsl -lm -lc -L/usr/local/lib -lusb
However i get:
testlibusb.c:27: error: 'true' undeclared here (not in a function)
testlibusb.c:146: error: conflicting types for 'read'
/usr/include/unistd.h:312: error: previous declaration of 'read' was here
testlibusb.c: In function 'read':
testlibusb.c:170: error: 'for' loop initial declaration used outside C99 mode
testlibusb.c: At top level:
testlibusb.c:180: error: conflicting types for 'write'
/usr/include/unistd.h:318: error: previous declaration of 'write' was here
testlibusb.c: In function 'write':
testlibusb.c:214: error: 'for' loop initial declaration used outside C99 mode
testlibusb.c: In function 'readWriteLoop':
testlibusb.c:313: error: 'for' loop initial declaration used outside C99 mode
testlibusb.c:318: error: 'for' loop initial declaration used outside C99 mode
testlibusb.c:335: error: 'for' loop initial declaration used outside C99 mode
testlibusb.c: In function 'main':
testlibusb.c:368: error: 'bool' undeclared (first use in this function)
testlibusb.c:368: error: (Each undeclared identifier is reported only once
testlibusb.c:368: error: for each function it appears in.)
testlibusb.c:368: error: expected ';' before 'run'
testlibusb.c:423: error: 'run' undeclared (first use in this function)
testlibusb.c:434: error: 'false' undeclared (first use in this function)
testlibusb.c:466:2: warning: no newline at end of file
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