Re: [PATCH v2 net-next 8/9] bpf: nfp: Report bpf_prog ID during XDP_QUERY_PROG

[Jakub Kicinski <jakub.kicinski@netronome.com>]

On Tue, 13 Jun 2017 14:08:40 -0700, Martin KaFai Lau wrote:
> -	case XDP_QUERY_PROG:
> -		xdp->prog_attached = !!nn->dp.xdp_prog;
> +	case XDP_QUERY_PROG: {
> +		const struct bpf_prog *xdp_prog;
> +
> +		xdp_prog = nn->dp.xdp_prog;
> +		if (xdp_prog) {
> +			xdp->prog_id = xdp_prog->aux->id;
> +			xdp->prog_attached = true;
> +		} else {
> +			xdp->prog_id = 0;
> +			xdp->prog_attached = false;
> +		}
>  		return 0;
> +	}

I'm sorry to nit pick but it could be done on a single line:

	case XDP_QUERY_PROG:
		xdp->prog_attached = !!nn->dp.xdp_prog;
+		xdp->prog_id = nn->dp.xdp_prog ? nn->dp.xdp_prog->aux->id : 0;
 		return 0;
 	default:
 		return -EINVAL;


What would be even cooler is a helper like this:

static inline u32 bpf_prog_id(struct bpf_prog *prog)
{
	if (!prog)
		return 0;
	return prog->aux->id;
}

in linux/bpf.h.  

In patch 1 I would be tempted to add a new command for getting the prog
id, instead of muxing through query to avoid the output parameter?  But
I'm OK with the code as is, its just a preference rather than an objection :)