netdev - Re: [PATCH net-next 1/3] tools: ynl-gen: use correct len for string and binary

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Date: Sat, 16 Dec 2023 16:35:40 +0800
From: Hangbin Liu <liuhangbin@...il.com>
To: Jakub Kicinski <kuba@...nel.org>
Cc: netdev@...r.kernel.org, Paolo Abeni <pabeni@...hat.com>
Subject: Re: [PATCH net-next 1/3] tools: ynl-gen: use correct len for string
 and binary

On Fri, Dec 15, 2023 at 06:06:03PM -0800, Jakub Kicinski wrote:
> On Fri, 15 Dec 2023 11:50:07 +0800 Hangbin Liu wrote:
> > As the description of 'struct nla_policy', the len means the maximum length
> > of string, binary. Or minimum length of attribute payload for others.
> > But most time we only use it for string and binary.
> 
> The meaning of 'len' in nla_policy is confusing to people writing new
> families. IIRC I used max-len / min-len / extact-len and not len on
> purpose in the YAML, so that there's no confusion what means what for
> which type...
> 
> Obviously it is slightly confusing for people like you who convert
> the existing families to YAML specs, but the risk of bugs seems lower
> there. So I'd prefer to stick to the existing set of options.
> 
> Is the existing code gen incorrect or just hard to wrap one's head
> around?
> 

The max-len / min-len / extact-len micro are used by binary. For string we
need to use "len" to define the max length. e.g.

static const struct nla_policy
team_nl_option_policy[TEAM_ATTR_OPTION_MAX + 1] = {
        [TEAM_ATTR_OPTION_UNSPEC]               = { .type = NLA_UNSPEC, },
        [TEAM_ATTR_OPTION_NAME] = {
                .type = NLA_STRING,
                .len = TEAM_STRING_MAX_LEN,
        },

Thanks
Hangbin