[dpdk-dev] [PATCH 0/19] Separate compile time linkage between eal lib and pmd's

[Neil Horman]

Disconnect compile time linkage between eal library / applications and pmd's

I noticed that, while tinkering with dpdk, building for shared libraries still
resulted in all the test applications linking to all the built pmd's, despite
not actually needing them all.  We are able to tell an application at run time
(via the -d/--blacklist/--whitelist/--vdev options) which pmd's we want to use, and
so have no need to link them at all. The only reason they get pulled in is
because rte_eal_non_pci_init_etherdev and rte_pmd_init_all contain static lists
to the individual pmd init functions. The result is that, even when building as
DSO's, we have to load all the pmd libraries, which is space inefficient and
defeating of some of the purpose of shared objects. 

To correct this, I developed this patch series, which introduces two new macros,
PMD_INIT_NONPCI and PMD_INIT.  These two macros use constructors to register
their init routines at runtime, either prior to the execution of main() when
linked statically, or when dlopen is called on a DSO at run time.  The result is
that PMD's can be loaded at run time without the application or eal library
having to hold a reference to them.  They work in a very simmilar fashion to the
module_init routine in the linux kernel.

I've tested this feature using the igb and pcap pmd's, both statically and
dynamically linked with the test and testpmd sample applications, and it seems
to work well.

Note, I encountered  a few bugs along the way, which I fixed and noted in the
series.

Regards
Neil