libibverbs init.c: conditionally emit warning if no userspace driver found

It's not a warning or an error if libibverbs cannot find a userspace
driver for kernel devices.  Indeed, returning a num_devices of is
sufficient -- the middleware shouldn't be unconditionally printing out
stderr message; let the upper layer application do that (if it wants
to).

For debugging purposes, if the environment variable IBV_SHOW_WARNINGS
is set (to any value), warnings will be emitted to stderr if a
corresponding userspace driver cannot be found for a kernel device.

Signed-off-by: Jeff Squyres <jsquyres@cisco.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>

2 files changed, 7 insertions, 1 deletions

diff --git a/man/ibv_get_device_list.3 b/man/ibv_get_device_list.3
index 16cc1a0..96de554 100644
--- a/man/ibv_get_device_list.3
+++ b/man/ibv_get_device_list.3
@@ -50,6 +50,12 @@ Client code should open all the devices it intends to use with
 Once it frees the array with
 .B ibv_free_device_list()\fR,
 it will be able to use only the open devices; pointers to unopened devices will no longer be valid.
+.P
+Setting the environment variable
+.BR IBV_SHOW_WARNINGS
+will cause warnings to be emitted to stderr if a kernel verbs device
+is discovered, but no corresponding userspace driver can be found for
+it.
 .SH "SEE ALSO"
 .BR ibv_fork_init (3),
 .BR ibv_get_device_name (3),
diff --git a/src/init.c b/src/init.c
index d0e4b1c..dbdd795 100644
--- a/src/init.c
+++ b/src/init.c
@@ -561,7 +561,7 @@ out:
 		     next_dev = sysfs_dev ? sysfs_dev->next : NULL;
 	     sysfs_dev;
 	     sysfs_dev = next_dev, next_dev = sysfs_dev ? sysfs_dev->next : NULL) {
-		if (!sysfs_dev->have_driver) {
+		if (!sysfs_dev->have_driver && getenv("IBV_SHOW_WARNINGS")) {
 			fprintf(stderr, PFX "Warning: no userspace device-specific "
 				"driver found for %s\n", sysfs_dev->sysfs_path);
 			if (statically_linked)