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Diffstat (limited to 'libusb-1.0/PORTING')
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diff --git a/libusb-1.0/PORTING b/libusb-1.0/PORTING deleted file mode 100644 index 7070784..0000000 --- a/libusb-1.0/PORTING +++ /dev/null @@ -1,95 +0,0 @@ -PORTING LIBUSB TO OTHER PLATFORMS - -Introduction -============ - -This document is aimed at developers wishing to port libusb to unsupported -platforms. I believe the libusb API is OS-independent, so by supporting -multiple operating systems we pave the way for cross-platform USB device -drivers. - -Implementation-wise, the basic idea is that you provide an interface to -libusb's internal "backend" API, which performs the appropriate operations on -your target platform. - -In terms of USB I/O, your backend provides functionality to submit -asynchronous transfers (synchronous transfers are implemented in the higher -layers, based on the async interface). Your backend must also provide -functionality to cancel those transfers. - -Your backend must also provide an event handling function to "reap" ongoing -transfers and process their results. - -The backend must also provide standard functions for other USB operations, -e.g. setting configuration, obtaining descriptors, etc. - - -File descriptors for I/O polling -================================ - -For libusb to work, your event handling function obviously needs to be called -at various points in time. Your backend must provide a set of file descriptors -which libusb and its users can pass to poll() or select() to determine when -it is time to call the event handling function. - -On Linux, this is easy: the usbfs kernel interface exposes a file descriptor -which can be passed to poll(). If something similar is not true for your -platform, you can emulate this using an internal library thread to reap I/O as -necessary, and a pipe() with the main library to raise events. The file -descriptor of the pipe can then be provided to libusb as an event source. - - -Interface semantics and documentation -===================================== - -Documentation of the backend interface can be found in libusbi.h inside the -usbi_os_backend structure definition. - -Your implementations of these functions will need to call various internal -libusb functions, prefixed with "usbi_". Documentation for these functions -can be found in the .c files where they are implemented. - -You probably want to skim over *all* the documentation before starting your -implementation. For example, you probably need to allocate and store private -OS-specific data for device handles, but the documentation for the mechanism -for doing so is probably not the first thing you will see. - -The Linux backend acts as a good example - view it as a reference -implementation which you should try to match the behaviour of. - - -Getting started -=============== - -1. Modify configure.ac to detect your platform appropriately (see the OS_LINUX -stuff for an example). - -2. Implement your backend in the libusb/os/ directory, modifying -libusb/os/Makefile.am appropriately. - -3. Add preprocessor logic to the top of libusb/core.c to statically assign the -right usbi_backend for your platform. - -4. Produce and test your implementation. - -5. Send your implementation to libusb-devel mailing list. - - -Implementation difficulties? Questions? -======================================= - -If you encounter difficulties porting libusb to your platform, please raise -these issues on the libusb-devel mailing list. Where possible and sensible, I -am interested in solving problems preventing libusb from operating on other -platforms. - -The libusb-devel mailing list is also a good place to ask questions and -make suggestions about the internal API. Hopefully we can produce some -better documentation based on your questions and other input. - -You are encouraged to get involved in the process; if the library needs -some infrastructure additions/modifications to better support your platform, -you are encouraged to make such changes (in cleanly distinct patch -submissions). Even if you do not make such changes yourself, please do raise -the issues on the mailing list at the very minimum. - |