Re: [PATCH v9 bpf-next 02/14] xdp: introduce flags field in xdp_buff/xdp_frame

On Mon, Jun 14, 2021 at 5:50 AM Lorenzo Bianconi [off-list ref] wrote:

quoted

Introduce flags field in xdp_frame/xdp_buffer data structure
to define additional buffer features. At the moment the only
supported buffer feature is multi-buffer bit (mb). Multi-buffer bit
is used to specify if this is a linear buffer (mb = 0) or a multi-buffer
frame (mb = 1). In the latter case the shared_info area at the end of
the first buffer will be properly initialized to link together
subsequent buffers.

Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>

Instead of passing this between buffers and frames I wonder if this
wouldn't be better to place in something like the xdp_mem_info
structure since this is something that would be specific to how the
device is handling memory anyway. You could probably split the type
field into a 16b type and a 16b flags field. Then add your bit where 0
is linear/legacy and 1 is scatter-gather/multi-buffer.

ack, this should be fine but I put the flag field in xdp_buff/xdp_frame
in order to reuse it for some xdp hw-hints (e.g rx checksum type).
We can put it in xdp_mem_info too but I guess it would be less intuitive, what
do you think?

Regards,
Lorenzo