[dpdk-dev] [PACTH v3 2/2] mlx4: fix shared library dependency

[Nelio Laranjeiro <nelio.laranjeiro@6wind.com>]

librte_pmd_mlx4.so needs to be linked with libibverbs otherwise, the PMD is
not able to open Mellanox devices and the following message is printed by
testpmd at startup
"librte_pmd_mlx4: cannot access device, is mlx4_ib loaded?".

Applications dependency on libibverbs are moved to be only valid in static
mode, in shared mode, applications do not depend on it anymore,
librte_pmd_mlx4.so keeps this dependency and thus is linked with libibverbs.

MLX4 cannot be supported in combined shared library because there is no clean
way of adding -libverbs to the combined library.

Signed-off-by: Nelio Laranjeiro <nelio.laranjeiro@6wind.com>
Acked-by: Olivier Matz <olivier.matz@6wind.com>
---
Changelog: fail the compilation of the PMD when the configuration is not
supported.

 doc/guides/nics/mlx4.rst  | 5 +++++
 drivers/net/mlx4/Makefile | 7 +++++++
 mk/rte.app.mk             | 3 +++
 3 files changed, 15 insertions(+)

diff --git a/doc/guides/nics/mlx4.rst b/doc/guides/nics/mlx4.rst
index c33aa38..562db06 100644
--- a/doc/guides/nics/mlx4.rst
+++ b/doc/guides/nics/mlx4.rst
@@ -47,6 +47,11 @@ There is also a `section dedicated to this poll mode driver
    be enabled manually by setting ``CONFIG_RTE_LIBRTE_MLX4_PMD=y`` and
    recompiling DPDK.
 
+.. warning::
+
+   ``CONFIG_RTE_BUILD_COMBINE_LIBS`` with ``CONFIG_RTE_BUILD_SHARED_LIB``
+   is not supported and thus the compilation will fail with this configuration.
+
 Implementation details
 ----------------------
 
diff --git a/drivers/net/mlx4/Makefile b/drivers/net/mlx4/Makefile
index 14cb53f..0399aff 100644
--- a/drivers/net/mlx4/Makefile
+++ b/drivers/net/mlx4/Makefile
@@ -31,6 +31,12 @@
 
 include $(RTE_SDK)/mk/rte.vars.mk
 
+ifeq ($(CONFIG_RTE_BUILD_COMBINE_LIBS)$(CONFIG_RTE_BUILD_SHARED_LIB),yy)
+$(info MLX4: Not supported in a combined shared library)
+all:
+	false
+endif
+
 # Library name.
 LIB = librte_pmd_mlx4.a
 
@@ -50,6 +56,7 @@ CFLAGS += -g
 CFLAGS += -I.
 CFLAGS += -D_XOPEN_SOURCE=600
 CFLAGS += $(WERROR_FLAGS)
+LDLIBS += -libverbs
 
 # A few warnings cannot be avoided in external headers.
 CFLAGS += -Wno-error=cast-qual
diff --git a/mk/rte.app.mk b/mk/rte.app.mk
index 97719cb..3871205 100644
--- a/mk/rte.app.mk
+++ b/mk/rte.app.mk
@@ -100,7 +100,10 @@ ifeq ($(CONFIG_RTE_LIBRTE_VHOST_USER),n)
 _LDLIBS-$(CONFIG_RTE_LIBRTE_VHOST)          += -lfuse
 endif
 
+ifeq ($(CONFIG_RTE_BUILD_SHARED_LIB),n)
 _LDLIBS-$(CONFIG_RTE_LIBRTE_MLX4_PMD)       += -libverbs
+endif # ! CONFIG_RTE_BUILD_SHARED_LIBS
+
 _LDLIBS-$(CONFIG_RTE_LIBRTE_BNX2X_PMD)      += -lz
 
 _LDLIBS-y += --start-group
-- 
1.9.1