Re: [RFC PATCH 1/5] IB/core: Add Core Capability flags to ib_device

[Doug Ledford <dledford-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>]

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On Mon, 2015-05-04 at 16:53 +0000, Hefty, Sean wrote:
> > > >  struct ib_port_attr {
> > > >  	enum ib_port_state	state;
> > > >  	enum ib_mtu		max_mtu;
> > > >  	enum ib_mtu		active_mtu;
> > > >  	int			gid_tbl_len;
> > > > +	u64                     core_cap_flags;
> > > >  	u32			port_cap_flags;
> > > >  	u32			max_msg_sz;
> > > >  	u32			bad_pkey_cntr;
> > > > @@ -1684,6 +1705,7 @@ struct ib_device {
> > > >  	u32			     local_dma_lkey;
> > > >  	u8                           node_type;
> > > >  	u8                           phys_port_cnt;
> > > > +	u64                         *core_cap_flags; /* Per port core
> > > > capability flags */
> > >
> > > Why are the core_cap_flags duplicated in the struct and in port
> > attributes?
> > 
> > Because the per port ib_port_attr struct is not visible to the core
> > code, it must call ib_query_port each time it wants to see it.  In order
> > to make the helpers avoid a call, you have to stash the cap_flags into
> > the ib_device struct.  In the past, the only thing there was the
> > node_type, and it was per device and not per node.  In order to make all
> > of this work and not require calls into the driver all the time, that
> > has to change to a per-port array.  Eventually we could get rid of the
> > node_type element once everything is in place.
> 
> I understand why they are in struct ib_device, but why are they duplicated in struct ib_port_attr?

Because ib_query_port returns a struct, so this must be an element of
that struct or it can't be returned (without adding a new, single use
driver upcall).

-- 
Doug Ledford <dledford-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
              GPG KeyID: 0E572FDD



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