Re: [PATCH] crypto: compress - Add pcomp interface

[Herbert Xu]

On Thu, Feb 19, 2009 at 10:12:18AM +0100, Geert Uytterhoeven wrote:
>
> IIUC, my setup() routines should decode the parameters using nla_parse()?

Right.

> And the caller of a setup() routine should encode the data. But how? All the
> nla_put*() routines seem to be targeted at skb's.

The callers in the kernel should just lay it out on the stack, e.g.,

	struct {
		struct nlattr foo;
		u32 foo_val;
		struct nlattr bar;
		u32 bar_val;
		...
	};

Note that the netlink alignment is 4 so u32 doesn't need any padding
though u8/u16 would need padding before the next nlattr.  Although
for our purposes u32 should be sufficient.

> The only place where nla_parse() is called with a void */length pair is
> net/sched/em_meta.c:em_meta_change(). But I can find no place where the actual
> TCA_EM_META_* fields are encoded.

For simple things like u32 the format is just header followed by
the u32.  See nla_get_u32 for details.

Cheers,
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