Documenation for the hidraw driver. Signed-off-by: Alan Ott <alan@xxxxxxxxxxx> --- The information in this patch relies on: [PATCH v2] HID: Add Support for Setting and Getting Feature Reports from hidraw which has been applied by Jiri Kosina. Please provide comments. I'm sure someone here will have a better idea where to put this than the root of Documentation/. I didn't see a better place, as hidraw is used for both Bluetooth and USB. Documentation/hidraw.txt | 283 ++++++++++++++++++++++++++++++++++++++++++++++ 1 files changed, 283 insertions(+), 0 deletions(-) create mode 100644 Documentation/hidraw.txt diff --git a/Documentation/hidraw.txt b/Documentation/hidraw.txt new file mode 100644 index 0000000..7153a06 --- /dev/null +++ b/Documentation/hidraw.txt @@ -0,0 +1,283 @@ + HIDRAW - Raw Access to USB and Bluetooth Human Interface Devices + ================================================================== + +The hidraw driver provides a raw interface to USB and Bluetooth Human +Interface Devices (HIDs). It differs from hiddev in that reports sent and +received are not parsed by the HID parser, but are sent to and received from +the device unmodified. + +Hidraw should be used if the userspace application knows exactly how to +communicate with the hardware device, and is able to construct the HID +reports manually. This is often the case when making userspace drivers for +custom HID devices. + +Hidraw is also useful for communicating with non-conformant HID devices +which send and receive data in a way that is inconsistent with their report +descriptors. Because hiddev parses reports which are sent and received +through it and checks them against the device's report descriptor, such +communication with these non-conformant devices is impossible using hiddev. + +Hidraw uses a dynamic major number, meaning that udev should be relied on to +create hidraw device nodes. Udev will typically create the device nodes +directly under /dev (eg: /dev/hidraw0). As this location is distribution- +and udev rule-dependent, applications should use libudev to locate hidraw +devices attached to the system. There is a tutorial on libudev with a +working example at: + http://www.signal11.us/oss/udev/ + +The HIDRAW API +--------------- + +read() +------- +read() will read a queued report received from the HID device. On USB +devices, the reports read using read() are the reports sent from the device +on the INTERRUPT IN endpoint. By default, read() will block until there is +a report available to be read. read() can be made non-blocking, by passing +the O_NONBLOCK flag to open(), or by setting the O_NONBLOCK flag using +fcntl(). + +On a device which uses numbered reports, the first byte of the returned data +will be the report number; the report data follows, beginning in the second +byte. For devices which do not use numbered reports, the report data +will begin at the first byte. + +write() +-------- +The write() function will write a report to the device. For USB devices, if +the device has an INTERRUPT OUT endpoint, the report will be sent on that +endpoint. If it does not, the report will be sent over the control endpoint, +using a SET_REPORT transfer. + +The first byte of the buffer passed to write() should be set to the report +number. If the device does not use numbered reports, the first byte should +be set to 0. The report data itself should begin at the second byte. + +ioctl() +-------- +Hidraw supports the following ioctls: + +HIDIOCGRDESCSIZE: Get Report Descriptor Size +This ioctl will get the size of the device's report descriptor. + +HIDIOCGRDESC: Get Report Descriptor +This ioctl returns the device's report descriptor using a +hidraw_report_descriptor struct. Make sure to set the size field of the +hidraw_report_descriptor struct to the size returned from HIDIOCGRDESCSIZE. + +HIDIOCGRAWINFO: Get Raw Info +This ioctl will return a hidraw_devinfo struct containing the bus type, the +vendor ID (VID), and product ID (PID) of the device. The bus type can be one +of: + BUS_USB + BUS_HIL + BUS_BLUETOOTH + BUS_VIRTUAL +which are defined in linux/input.h. + +HIDIOCGRAWNAME(len): Get Raw Name +This ioctl returns a string containing the vendor and product strings of +the device. The returned string is Unicode, UTF-8 encoded. + +HIDIOCGRAWPHYS(len): Get Physical Address +This ioctl returns a string representing the physical address of the device. +For USB devices, the string contains the physical path to the device (the +USB controller, hubs, ports, etc). For Bluetooth devices, the string +contains the hardware (MAC) address of the device. + +HIDIOCSFEATURE(len): Send a Feature Report +This ioctl will send a feature report to the device. Per the HID +specification, feature reports are always sent using the control endpoint. +Set the first byte of the supplied buffer to the report number. For devices +which do not use numbered reports, set the first byte to 0. The report data +begins in the second byte. Make sure to set len accordingly, to one more +than the length of the report (to account for the report number). + +HIDIOCGFEATURE(len): Get a Feature Report +This ioctl will request a feature report from the device using the control +endpoint. The first byte of the supplied buffer should be set to the report +number of the requested report. For devices which do not use numbered +reports, set the first byte to 0. The report will be returned starting at +the first byte of the buffer (ie: the report number is not returned). + +Example +--------- +The following code shows examples of read() write() and all the ioctls for +hidraw. The code may be used by anyone for any purpose, and can serve as a +starting point for developing applications using hidraw. + +---- Begin Code ---- +/******************************* + Hidraw test + (c) Alan Ott + May be used for any purpose. +*******************************/ + +/* Linux */ +#include <linux/types.h> +#include <linux/input.h> +#include <linux/hidraw.h> + +/* Unix */ +#include <sys/ioctl.h> +#include <sys/types.h> +#include <sys/stat.h> +#include <fcntl.h> +#include <unistd.h> + +/* C */ +#include <stdio.h> +#include <string.h> +#include <stdlib.h> +#include <errno.h> + +const char *bus_str(int bus); + +int main(int argc, char **argv) +{ + int fd; + + /* Open the Device with non-blocking reads. In real life, + don't use a hard coded path; use libudev instead. */ + fd = open("/dev/hidraw0", O_RDWR|O_NONBLOCK); + + if (fd > 0) { + int i, res, desc_size = 0; + char buf[256]; + struct hidraw_report_descriptor rpt_desc; + struct hidraw_devinfo info; + + memset(&rpt_desc, 0, sizeof(rpt_desc)); + memset(&info, 0xff, sizeof(info)); + memset(buf, 0x0, sizeof(buf)); + + /* Get Report Descriptor Size */ + res = ioctl(fd, HIDIOCGRDESCSIZE, &desc_size); + if (res < 0) + perror("HIDIOCGRDESCSIZE"); + else { + printf("Report Descriptor Size: %d\n", desc_size); + } + + /* Get Report Descriptor */ + rpt_desc.size = desc_size; + res = ioctl(fd, HIDIOCGRDESC, &rpt_desc); + if (res < 0) + perror("HIDIOCGRDESC"); + else { + printf("Report Descriptor:\n"); + for (i = 0; i < rpt_desc.size; i++) { + printf("%hhx ", rpt_desc.value[i]); + } + puts("\n"); + } + + /* Get Raw Name */ + res = ioctl(fd, HIDIOCGRAWNAME(256), buf); + if (res < 0) + perror("HIDIOCGRAWNAME"); + else { + printf("Raw Name: %s\n", buf); + } + + /* Get Physical Location */ + res = ioctl(fd, HIDIOCGRAWPHYS(256), buf); + if (res < 0) + perror("HIDIOCGRAWPHYS"); + else { + printf("Raw Phys: %s\n", buf); + } + + /* Get Raw Info */ + res = ioctl(fd, HIDIOCGRAWINFO, &info); + if (res < 0) + perror("HIDIOCGRAWINFO"); + else { + printf("Raw Info:\n"); + printf("\tbustype: %d (%s)\n", info.bustype, bus_str(info.bustype)); + printf("\tvendor: 0x%04hx\n", info.vendor); + printf("\tproduct: 0x%04hx\n", info.product); + } + + /* Set Feature */ + buf[0] = 0x9; /* Report Number */ + buf[1] = 0xff; + buf[2] = 0xff; + buf[3] = 0xff; + res = ioctl(fd, HIDIOCSFEATURE(4), buf); + if (res < 0) + perror("HIDIOCSFEATURE"); + else { + printf("ioctl HIDIOCGFEATURE returned: %d\n", res); + } + + /* Get Feature */ + buf[0] = 0x9; /* Report Number */ + res = ioctl(fd, HIDIOCGFEATURE(256), buf); + if (res < 0) + perror("HIDIOCGFEATURE"); + else { + printf("ioctl HIDIOCGFEATURE returned: %d\n", res); + printf("Report data (not containing the report number): \n\t"); + for (i = 0; i < res; i++) { + printf("%hhx ", buf[i]); + } + puts("\n"); + } + + /* Send a Report to the Device */ + buf[0] = 0x1; /* Report Number */ + buf[1] = 0x77; + res = write(fd, buf, 2); + if (res < 0) { + printf("Error: %d\n", errno); + perror("write"); + } + else + printf("write() wrote %d bytes\n", res); + + /* Get a report from the device */ + res = read(fd, buf, 16); + if (res < 0) { + perror("read"); + } + else { + printf("read() read %d bytes:\n\t", res); + for (i = 0; i < res; i++) { + printf("%hhx ", buf[i]); + } + puts("\n"); + } + close(fd); + } + else { + perror("Unable to open device"); + } + return 0; +} + +const char * +bus_str(int bus) +{ + switch(bus) { + case BUS_USB: + return "USB"; + break; + case BUS_HIL: + return "HIL"; + break; + case BUS_BLUETOOTH: + return "Bluetooth"; + break; + case BUS_VIRTUAL: + return "Virtual"; + break; + default: + return "Other"; + break; + } +} +---- End Code ---- + +Document by: + Alan Ott <alan@xxxxxxxxxxx> -- 1.7.0.4 -- To unsubscribe from this list: send the line "unsubscribe linux-input" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
