Re: [PATCH v1 1/5] IB/uverbs: ex_query_device: answer must not depend on request's comp_mask

On 05/02/2015 04:54, Weiny, Ira wrote:

quoted

On Thu, Jan 29, 2015 at 09:50:38PM +0100, Yann Droneaud wrote:

quoted

Anyway, I recognize that uverb way of abusing write() syscall is
borderline (at best) regarding other Linux subsystems and Unix
paradigm in general. But it's not enough to screw it more.

Then we must return the correct output size explicitly in the struct.

I was thinking this very same thing as I read through this thread.

I too would like to avoid the use of comp_masks if at all possible.  The query call seems to be a verb where the structure size is all you really need to know the set of values returned.

As Jason says, other calls may require the comp_mask where 0 is not sufficient to indicate "missing".

Would it be okay to return it in the ib_uverbs_cmd_hdr.out_words? That
would further abuse the write() syscall by writing to the input buffer.
However, the only other alternative I see is to add it explicitly to
every uverb response struct.

Haggai