[openib-general] RE: [PATCH 1 of 3] mad: large RMPP support

[Sean Hefty]

Based on what you've done, I'd like to suggest changing interface similar to
that shown below.  I believe that this could be done with minor changes to the
current patches.  Detailed comments that led to suggesting this change are
inline in my responses.

struct ib_mad_segments {
	u32			num_segments;
	u32			segment_size;
	void			*segment[0];
};

struct ib_mad_send_buf {
	...
	void			*mad; /* First MAD segment */
	struct ib_mad_segments	*segments;	/* RMPP segments > 1 */
	...
};

This will avoid walking through a list to find segments, and allows for
efficient allocation of the segment data buffers.  Multiple segments could be
allocated through a single kzalloc.  (For example, every n-th segment would
start a new allocation, making deallocation easy as well.)


>+struct ib_mad_multipacket_seg {
>+	struct list_head list;
>+	u32 size;
>+	u8 data[0];
>+};

Should we ensure that the data alignment is on a 64-byte boundary?

> struct ib_mad_send_buf {
> 	struct ib_mad_send_buf	*next;
>-	void			*mad;
>+	void			*mad; /* RMPP: first segment,
>+					 including the MAD header */
>+	void			*mad_payload; /* RMPP: changed per segment */

Mad_payload doesn't appear to be directly accessible directly by the user.  It
should be hidden.

- Sean