Re: [PATCH for-next V2 2/9] IB/core: Change ib_create_cq to use struct ib_cq_init_attr

[Jason Gunthorpe <jgunthorpe-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>]

On Tue, Jun 02, 2015 at 10:29:14AM +0300, Matan Barak wrote:
> On Mon, Jun 1, 2015 at 7:53 PM, Jason Gunthorpe
> <jgunthorpe-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org> wrote:
> > On Sun, May 31, 2015 at 03:14:10PM +0300, Or Gerlitz wrote:
> >
> >> +     struct ib_cq_init_attr cq_attr;
> >>
> >>       /* Create new device info */
> >>       port_priv = kzalloc(sizeof *port_priv, GFP_KERNEL);
> >> @@ -2943,9 +2944,11 @@ static int ib_mad_port_open(struct ib_device *device,
> >>       if (has_smi)
> >>               cq_size *= 2;
> >>
> >> +     memset(&cq_attr, 0, sizeof(cq_attr));
> >> +     cq_attr.cqe = cq_size;
> >
> > Why does this patch switch to using memset when the prior patch used
> > = {} ?
> >
> 
> Why does it matter? Both are valid approaches, aren't they?

Sure, but why mix and match techniques in the same code base? Is there
a reason?

> >> @@ -1075,12 +1075,11 @@ EXPORT_SYMBOL(ib_destroy_qp);
> >>  struct ib_cq *ib_create_cq(struct ib_device *device,
> >>                          ib_comp_handler comp_handler,
> >>                          void (*event_handler)(struct ib_event *, void *),
> >> -                        void *cq_context, int cqe, int comp_vector)
> >> +                        void *cq_context, struct ib_cq_init_attr *cq_attr)
> >>  {
> >>       struct ib_cq *cq;
> >> -     struct ib_cq_init_attr attr = {.cqe = cqe, .comp_vector = comp_vector};
> >>
> >> -     cq = device->create_cq(device, &attr, NULL, NULL);
> >> +     cq = device->create_cq(device, cq_attr, NULL, NULL);
> >
> > How does this compile without warnings?
> >
> 
> Do you mean that there's a missing const here? It doesn't (and shouldn't)
> cause warnings.

Warnings will be emitted when you compile with -Wcast-qual (make W=3).

Some of the static tools may warn/error on implicitly casting away
const, I'm not sure.

It is broadly undesirable to implicitly cast away const, even if the
Kernel warning defaults don't produce the message.

Jason
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