[dpdk-dev] [PATCH v5 00/14] dpdk: 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 a new macro,
PMD_REGISTER_DRIVER, which wraps up Oliviers work using constructors on the
virtual device pmds, then expands on it to include the physical device pmds,
allowing us to break linkages between dpdk applications and pmd's almost
entirely (save for the ring and xenvirt drivers, which have additional api's
outside of the standard dpdk code that we need to further fix).  This also
allows us to completely remove the rte_pmd_init_all routine, hiding its function
internally to the rte_eal_init path.

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

Change Notes:

1) Reposted the entire series.  Recent changes permeated accross several
patches, and since a few patches already had multiple versions, I've reposted
the entire series and bumped the version number to 5, whcih skips a few
versions, but ensures this series is seen as the most recent.

2) Merged the PMD_REGISTER_DRIVER macro into rte_dev.h, which is a better
location for it.  Required removing include of rte_pmd.h across most of the
patches in the series.

3) Cleaned up various leftover "virtual" comments in the driver registration api
that no longer belong there after making it generic

4) Fixed the LINK_USING_CC check in rte.lib.mk so it works like other uses

5) Fixed CPU_LDFLAGS conversion to use -Wl in case we link with gcc.