Comtrol eCos - Manual (Page 770)

Writing New Devices - target
defined point at which the I/O auxiliary knows that all required devices have been loaded. It can then perform
various consistency checks and clean-ups, run the user’s
mainrc.tcl script, and make the main window visible.
For standard devices generic eCos I/O code will call the device initialization routines at the right time, iterating
through the
DEVTAB table in a static constructor. The same holds for network devices and file systems. For more
custom devices code like the following can be used:
#include < cyg/infra/cyg_type.h >
class mydev_init {
public:
mydev_init() {
...
}
};
static mydev_init mydev_init_object CYGBLD_ATTRIB_INIT_PRI(CYG_INIT_IO);
Some care has to be taken because the object mydev_init_object will typically not be referenced by other code,
and hence may get eliminated at link-time. If the code is part of an eCos package then problems can be avoided by
putting the relevant file in
libextras.a :
cdl_package CYGPKG_DEVS_MINE {
...
compile -library=libextras.a init.cxx
}
For devices inside application code the same can be achieved by linking the relevant module as a .o file rather than
putting it in a .a library.
In the device initialization routine the main operation is a call to synth_auxiliary_instantiate . This takes
five arguments, all of which should be strings:
package
For device drivers which are eCos packages this should be a directory path relative to the eCos repository,
for example
devs/eth/synth/ecosynth . This will allow the I/O auxiliary to find the various host-side
support files for this package within the install tree. If the device is application-specific and not part of an
eCos package then a NULL pointer can be used, causing the I/O auxiliary to search for the support files in the
current directory and then in
~/.ecos/synth instead.
version
For eCos packages this argument should be the version of the package that is being used, for example cur-
rent . A simple way to get this version is to use the SYNTH_MAKESTRING macro on the package name. If the
device is application-specific then a NULL pointer should be used.
device
This argument specifies the type of device being instantiated, for example ethernet . More specifically the
I/O auxiliary will append a .tcl suffix, giving the name of a Tcl script that will handle all I/O requests for
the device. If the application requires several instances of a type of device then the script will only be loaded
once, but the script will contain an instantiation procedure that will be called for each device instance.
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