Re: What is the reason to...

[Bart Veer <bartv at ecoscentric dot com>]

>>>>> "Oliver" == oliver munz @ s p e a g <munz@speag.ch> writes:

    Oliver> mark CYGPKG_IO_SPI as HARDWARE?
    Oliver> I think Generic SPI or I2C and so one should be loadable
    Oliver> whitout an template. Can we change this?

The problem here is that other drivers such as the wallclock or
dataflash are likely to depend on the SPI/I2C bus being available. On
some platforms there may even be platform HAL dependencies on the bus.
Now, by convention you can enable flash support on a given platform
simply by e.g. "ecosconfig add flash" and everything sorts itself out.
If the SPI or I2C bus driver was not automatically part of the
configuration then that would stop working.

If you want the SPI or I2C support to be automatically available when
needed, working within the limitations of current CDL, then the
generic SPI or I2C packages have to be part of the target definition
in ecos.db. That means they have to be hardware packages.

Also, in most cases the expectation is that the generic SPI and I2C
packages will only be usable if the target definition also specifies a
device driver appropriate for the hardware. So if you are adding SPI
or I2C support to a target then you have to edit the ecos.db target
entry anyway, and adding two packages instead of one is no big deal.

Now, both the generic SPI and I2C packages have been carefully
designed to ensure that they add zero overhead to the application if
nothing actually uses the SPI or I2C bus. Any unused functionality
gets eliminated at link-time by linker garbage collection. Hence the
only real overhead is at build-time: ecosconfig or the configtool may
take a little longer to run, and a couple more files get compiled.
Neither is likely to be noticed by users unless they sit down with a
stopwatch.

Bart

-- 
Bart Veer                                   eCos Configuration Architect
eCosCentric Limited    The eCos experts      http://www.ecoscentric.com/
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