For certain basic functionality, there aren't much benefit to be able to
vary the implementation easily at runtime. So instead of using virtual
functions, use regular functions that are "resolved" at link time. The
implementation of such functions is provided per board/platform.
Examples of functions that fit this include: getting the current
time (since boot), panic'ing, getting system information, rebooting.
These functions are less likely to benefit from the indirection provided
by virtual interfaces. For more complex hardware access APIs the
indirection makes more sense and ease the testing (when we have it!).
The idea is that instead of calling
hal.scheduler->panic("on the streets of london");
now use
AP_HAL::panic("on the streets of london");
A less important side-effect is that call-site code gets
smaller. Currently the compiler needs to get the hal, get the scheduler
pointer, get the right function pointer in the vtable for that
scheduler. And the call must include an extra parameter ("this"). Now it
will be just a function call, with the address resolved at link time.
This patch introduces the first functions that will be in the namespace,
further patches will implementations for each board and then switch the
call-sites. The extra init() function allow any initial setup needed for
the functions to work.
prog_char and prog_char_t are now the same as char on supported
platforms. So, just change all places that use them and prefer char
instead.
AVR-specific places were not changed.
The PSTR is already define as a NOP for all supported platforms. It's
only needed for AVR so here we remove all the uses throughout the
codebase.
This was automated with a simple python script so it also converts
places which spans to multiple lines, removing the matching parentheses.
AVR-specific places were not changed.
Move the macros to a single place and reduce the variations not based on
board, but based on
- The name of the entry-point function, specified by AP_MAIN;
- Whether it contains argc/argv arguments or not.
The goal here is that programs (vehicles and examples) don't need to
include all possible boards to define a main function. Further patches
will change the programs.
Instead of requiring every program to specify the HAL related modules,
let the build system do it (in practice everything we compiled depended
on HAL anyway). This allow including only the necessary files in the
compilation.
The switching between different AP_HAL was happening by giving different
definitions of AP_HAL_BOARD_DRIVER, and the programs would use it to
instantiate.
A program or library code would have to explicitly include (and depend)
on the concrete implementation of the HAL, even when using it only via
interface.
The proposed change move this dependency to be link time. There is a
AP_HAL::get_HAL() function that is used by the client code. Each
implementation of HAL provides its own definition of this function,
returning the appropriate concrete instance.
Since this replaces the job of AP_HAL_BOARD_DRIVER, the definition was
removed.
The static variables for PX4 and VRBRAIN were named differently to avoid
shadowing the extern symbol 'hal'.
Now instead of requiring the buffer to fill completely before we can
detect it is not draining, we use a time based mechanism to detect
when none of the first few bytes are transmitted after sitting in our
buffer a half second or more after flow control is enabled. This
huristic is reliable only for the first several chracters because we
believe that the radio must still have plenty of room in it's own
buffers at that time even if it is not able to transmit them to the
other radio yet. Note that the original algorithm made the same
assumption.
The new algorithm is especially helpful for cases where only keepalive
messages are transmitted before other packets can be requested by the
GCS. In this situation, the original code required almost 2 minutes
to disable flow control and allow communication with the GCS.
This commit changes the way libraries headers are included in source files:
- If the header is in the same directory the source belongs to, so the
notation '#include ""' is used with the path relative to the directory
containing the source.
- If the header is outside the directory containing the source, then we use
the notation '#include <>' with the path relative to libraries folder.
Some of the advantages of such approach:
- Only one search path for libraries headers.
- OSs like Windows may have a better lookup time.
Andrew Tridgell
Caio Marcelo de Oliveira Filho
Lucas De Marchi
Tom Pittenger
Brad Bosch
Gustavo Jose de Sousa
Julien BERAUD
Eugene Shamaev
Randy Mackay