Subject: RE: [PATCH v2 iproute2-next 1/3] rdma: update rdma_netlink.h to get new driver attributes

From: "Steve Wise" <[email-masked]>
Date: Tue, 15 May 2018 15:25:58 -0500

> On Tue, 2018-05-15 at 13:37 -0600, David Ahern wrote:
> > On 5/14/18 9:42 AM, Steve Wise wrote:
> > > diff --git a/rdma/include/uapi/rdma/rdma_netlink.h
> b/rdma/include/uapi/rdma/rdma_netlink.h
> > > index 60416ed..40be0d8 100644
> > > --- a/rdma/include/uapi/rdma/rdma_netlink.h
> > > +++ b/rdma/include/uapi/rdma/rdma_netlink.h
> > > @@ -249,10 +249,22 @@ enum rdma_nldev_command {
> > >  	RDMA_NLDEV_NUM_OPS
> > >  };
> > >
> > > +enum {
> > > +	RDMA_NLDEV_ATTR_ENTRY_STRLEN = 16,
> > > +};
> > > +
> > > +enum rdma_nldev_print_type {
> > > +	RDMA_NLDEV_PRINT_TYPE_UNSPEC,
> > > +	RDMA_NLDEV_PRINT_TYPE_HEX,
> > > +};
> > > +
> > >  enum rdma_nldev_attr {
> > >  	/* don't change the order or add anything between, this is ABI! */
> >
> > I asked this before and did not get a response. As the comment above
> > states with an emphasis (!) ...

Sorry David, I missed your question previously. ☹

> >
> > >  	RDMA_NLDEV_ATTR_UNSPEC,
> > >
> > > +	/* Pad attribute for 64b alignment */
> > > +	RDMA_NLDEV_ATTR_PAD = RDMA_NLDEV_ATTR_UNSPEC,
> > > +
> >
> > ... are you really adding new attributes in the middle?
> 
> Not really.  The new item is being explicitly set to the same value as
> the item above it.  It therefore becomes two entries with the same enum
> value.  The rest of the enum is all unchanged.

Correct.

The reason this was done was because a kernel had already been released where 64b nlattrs were being padded with 0 instead of defining an explicit pad attribute.  Jason thought the kernel side should define an explicit PAD attribute and use it.  To preserve the ABI we defined it but set it to 0 (aka ATTR_UNSPEC aka the first in the enum).  

> 
> > >  	/* Identifier for ib_device */
> > >  	RDMA_NLDEV_ATTR_DEV_INDEX,		/* u32 */
> > >
> > > @@ -387,6 +399,20 @@ enum rdma_nldev_attr {
> > >  	RDMA_NLDEV_ATTR_RES_PD_ENTRY,		/* nested table */
> > >  	RDMA_NLDEV_ATTR_RES_LOCAL_DMA_LKEY,	/* u32 */
> > >  	RDMA_NLDEV_ATTR_RES_UNSAFE_GLOBAL_RKEY,	/* u32 */
> > > +	/*
> > > +	 * driver-specific attributes.
> > > +	 */
> > > +	RDMA_NLDEV_ATTR_DRIVER,			/* nested table */
> > > +	RDMA_NLDEV_ATTR_DRIVER_ENTRY,		/* nested table */
> > > +	RDMA_NLDEV_ATTR_DRIVER_STRING,		/* string */
> > > +	/*
> > > +	 * u8 values from enum rdma_nldev_print_type
> > > +	 */
> > > +	RDMA_NLDEV_ATTR_DRIVER_PRINT_TYPE,	/* u8 */
> > > +	RDMA_NLDEV_ATTR_DRIVER_S32,		/* s32 */
> > > +	RDMA_NLDEV_ATTR_DRIVER_U32,		/* u32 */
> > > +	RDMA_NLDEV_ATTR_DRIVER_S64,		/* s64 */
> > > +	RDMA_NLDEV_ATTR_DRIVER_U64,		/* u64 */
> >
> > and again here.
> >

Ugh, this looks like a mistake maybe due to me rebasing and not noticing this commit added the name/index attrs.

5b2cc79de878 [email-masked] RDMA/nldev: Provide netdevice name and index 

Both of these are in -next to be merged upstream together.  

Should I do anything?