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- There are two implementations of HIDAPI for Linux. One (hid.c) uses the
- Linux hidraw driver, and the other (hid-libusb.c) uses libusb. Which one you
- use depends on your application. Complete functionality of the hidraw
- version depends on patches to the Linux kernel which are not currently in
- the mainline. These patches have to do with sending and receiving feature
- reports. The libusb implementation uses libusb to talk directly to the
- device, bypassing any Linux HID driver. The disadvantage of the libusb
- version is that it will only work with USB devices, while the hidraw
- implementation will work with Bluetooth devices as well.
- To use HIDAPI, simply drop either hid.c or hid-libusb.c into your
- application and build using the build parameters in the Makefile.
- By default, on Linux, the Makefile in this directory is configured to use
- the libusb implementation. To switch to the hidraw implementation, simply
- change hid-libusb.c to hid.c in the Makefile.
- Libusb Implementation notes
- ----------------------------
- For the libusb implementation, libusb-1.0 must be installed. Libusb 1.0 is
- different than the legacy libusb 0.1 which is installed on many systems. To
- install libusb-1.0 on Ubuntu and other Debian-based systems, run:
- sudo apt-get install libusb-1.0-0-dev
- Hidraw Implementation notes
- ----------------------------
- For the hidraw implementation, libudev headers and libraries are required to
- build hidapi programs. To install libudev libraries on Ubuntu,
- and other Debian-based systems, run:
- sudo apt-get install libudev-dev
- On Redhat-based systems, run the following as root:
- yum install libudev-devel
- Unfortunately, the hidraw driver, which the linux version of hidapi is based
- on, contains bugs in kernel versions < 2.6.36, which the client application
- should be aware of.
- Bugs (hidraw implementation only):
- -----------------------------------
- On Kernel versions < 2.6.34, if your device uses numbered reports, an extra
- byte will be returned at the beginning of all reports returned from read()
- for hidraw devices. This is worked around in the libary. No action should be
- necessary in the client library.
- On Kernel versions < 2.6.35, reports will only be sent using a Set_Report
- transfer on the CONTROL endpoint. No data will ever be sent on an Interrupt
- Out endpoint if one exists. This is fixed in 2.6.35. In 2.6.35, OUTPUT
- reports will be sent to the device on the first INTERRUPT OUT endpoint if it
- exists; If it does not exist, OUTPUT reports will be sent on the CONTROL
- endpoint.
- On Kernel versions < 2.6.36, add an extra byte containing the report number
- to sent reports if numbered reports are used, and the device does not
- contain an INTERRPUT OUT endpoint for OUTPUT transfers. For example, if
- your device uses numbered reports and wants to send {0x2 0xff 0xff 0xff} to
- the device (0x2 is the report number), you must send {0x2 0x2 0xff 0xff
- 0xff}. If your device has the optional Interrupt OUT endpoint, this does not
- apply (but really on 2.6.35 only, because 2.6.34 won't use the interrupt
- out endpoint).
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