libibverbs: Fix query_device_ex dummy function not to return EOPNOTSUPP

[mkalderon]

Following thread on broken compatibility between v28 and older version:
https://www.spinics.net/lists/linux-rdma/msg89386.html

Implement query_device_ex dummy function for all providers.
Returning EOPNOTSUPP broke compatibility with apps compiled against
older rdma-core

Suggested-by: Jason Gunthorpe jgg@mellanox.com
Cc: stable@linux-rdma.org # v28
Fixes: commit c284107 ("libibverbs: Fix incorrect return code")
Signed-off-by: Michal Kalderon michal.kalderon@marvell.com

[mkalderon]

Jason, Sorry for the delay on this one...
A few comments / questions

1. I made the changes as you requested
2. Am able to run old app against new rdma-core succesfully
3. I only modified the signature in man pages -> not sure what exactlly you would like me to elaborate about
4. While making the change something popped up - I noticed that throughout rdma-core providers and some core, in some cases error are returned negative and in some not, such as -EINVAL or EINVAL, whether return codes are negative or positive is inconsistent -> do you have a guideline for this ?

[jgunthorpe]

errno's need to follow whatever is written in the man page

[nmorey]

Picked for stable-v28.
Older branches did not get the change to ENOTSUPP as I guessed (right apparently) it would break compatibility