netdev - Re: [PATCH net-next 1/6] net: nexthop: Add flag to assert that NHGRP reserved fields are zero

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Message-ID: <878qxanex2.fsf@nvidia.com>
Date: Tue, 6 Aug 2024 11:48:21 +0200
From: Petr Machata <petrm@...dia.com>
To: Jakub Kicinski <kuba@...nel.org>
CC: Petr Machata <petrm@...dia.com>, "David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>,
	<netdev@...r.kernel.org>, Ido Schimmel <idosch@...dia.com>, David Ahern
	<dsahern@...nel.org>, Donald Sharp <sharpd@...dia.com>, <mlxsw@...dia.com>
Subject: Re: [PATCH net-next 1/6] net: nexthop: Add flag to assert that
 NHGRP reserved fields are zero


Jakub Kicinski <kuba@...nel.org> writes:

> On Thu, 1 Aug 2024 18:23:57 +0200 Petr Machata wrote:
>> diff --git a/include/uapi/linux/nexthop.h b/include/uapi/linux/nexthop.h
>> index dd8787f9cf39..2ed643207847 100644
>> --- a/include/uapi/linux/nexthop.h
>> +++ b/include/uapi/linux/nexthop.h
>> @@ -33,6 +33,9 @@ enum {
>>  #define NHA_OP_FLAG_DUMP_STATS		BIT(0)
>>  #define NHA_OP_FLAG_DUMP_HW_STATS	BIT(1)
>>  
>> +/* Response OP_FLAGS. */
>> +#define NHA_OP_FLAG_RESP_GRP_RESVD_0	BIT(0)
>
> I guess these are op flags, so nobody should have a need to store them,
> but having bits mean different things in and out make decoding and
> binding generation much harder. Let's not do this unless absolutely
> necessary. Perhaps you can start defining response flags from the
> "other end", i.e. bit 31? Chances are the two sides will never "meet".

OK.