netdev - Re: [PATCH net-next v5 12/22] ethtool: provide string sets with GET

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Message-ID: <20190328173524.GR14297@nanopsycho>
Date:   Thu, 28 Mar 2019 18:35:24 +0100
From:   Jiri Pirko <jiri@...nulli.us>
To:     Michal Kubecek <mkubecek@...e.cz>
Cc:     Florian Fainelli <f.fainelli@...il.com>,
        David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
        Jakub Kicinski <jakub.kicinski@...ronome.com>,
        Andrew Lunn <andrew@...n.ch>,
        John Linville <linville@...driver.com>,
        Stephen Hemminger <stephen@...workplumber.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next v5 12/22] ethtool: provide string sets with
 GET_STRSET request

Thu, Mar 28, 2019 at 03:04:28PM CET, mkubecek@...e.cz wrote:
>On Thu, Mar 28, 2019 at 02:43:13PM +0100, Jiri Pirko wrote:
>> 
>> I don't like this. This should not be bitfield/set. This should be
>> simply nested array of enum values:
>> 
>> enum ethtool_link_mode {
>> 	ETHTOOL_LINK_MODE_10baseT_Half,
>> 	ETHTOOL_LINK_MODE_10baseT_Full,
>> 	ETHTOOL_LINK_MODE_100baseT_Half,
>> 	ETHTOOL_LINK_MODE_100baseT_Full,
>> 	ETHTOOL_LINK_MODE_1000baseT_Full,
>> };
>
>We already have such enum. The problem with your "no string" approach is
>that it requires all userspace applications to (1) keep this enum in

That is how it is usually done. UAPI defines ATTRS and values, userspace
assigns appropriate strings.


>sync with kernel and (2) maintain their our tables of names. Experience
>shows we are not very good and satisfying these conditions even for the
>one which should be best at keeping up.

Moreover, I think that speed, duplex and type should be sent
separatelly:

    ETHTOOL_A_LINK_MODE_LIST_OUR start nest
      ETHTOOL_A_LINK_MODE start nest
        ETHTOOL_A_LINK_MODE_SPEED = 100 /* this should be u64 */
	ETHTOOL_A_LINK_MODE_DUPLEX = ETHTOOL_LINK_MODE_DUPLEX_FULL
	ETHTOOL_A_LINK_MODE_TYPE = ETHTOOL_LINK_MODE_TYPE_BASET
      ETHTOOL_A_LINK_MODE start end
      ETHTOOL_A_LINK_MODE start nest
        ETHTOOL_A_LINK_MODE_SPEED = 10
	ETHTOOL_A_LINK_MODE_DUPLEX = ETHTOOL_LINK_MODE_DUPLEX_HALF
	ETHTOOL_A_LINK_MODE_TYPE = ETHTOOL_LINK_MODE_TYPE_BASET
      ETHTOOL_A_LINK_MODE start end
    ETHTOOL_A_LINK_MODE_LIST_PEER end nest

Does not really make sense to combine those 3 attributes together.


>
>> and then there should be 2 attrs:
>> ETHTOOL_A_LINK_MODE_LIST_OUR	/* nest */
>> ETHTOOL_A_LINK_MODE_LIST_PEER	/* nest */
>> ETHTOOL_A_LINK_MODE		/* u32 */
>> 
>> and then the message should look like:
>> 
>>    ETHTOOL_A_LINK_MODE_LIST_OUR start nest
>>      ETHTOOL_A_LINK_MODE = ETHTOOL_LINK_MODE_10baseT_Half
>>      ETHTOOL_A_LINK_MODE = ETHTOOL_LINK_MODE_10baseT_Full
>>      ETHTOOL_A_LINK_MODE = ETHTOOL_LINK_MODE_100baseT_Half
>>      ETHTOOL_A_LINK_MODE = ETHTOOL_LINK_MODE_100baseT_Full
>>      ETHTOOL_A_LINK_MODE = ETHTOOL_LINK_MODE_1000baseT_Full
>>    ETHTOOL_A_LINK_MODE_LIST_OUR end nest
>>    ETHTOOL_A_LINK_MODE_LIST_PEER start nest
>>      ETHTOOL_A_LINK_MODE = ETHTOOL_LINK_MODE_10baseT_Half
>>      ETHTOOL_A_LINK_MODE = ETHTOOL_LINK_MODE_10baseT_Full
>>      ETHTOOL_A_LINK_MODE = ETHTOOL_LINK_MODE_100baseT_Half
>>      ETHTOOL_A_LINK_MODE = ETHTOOL_LINK_MODE_100baseT_Full
>>      ETHTOOL_A_LINK_MODE = ETHTOOL_LINK_MODE_1000baseT_Full
>>    ETHTOOL_A_LINK_MODE_LIST_PEER end nest
>> 
>> Nice and simple. No bits, no strings.
>
>A bit too simple, actually. You would need third nest to distinguish

It is just an example.


>supported and advertised modes. And for setting, you would also need two
>arrays if you want to set only some of the modes (unless you introduce
>something that would be similar to mine except for omitting the names).
>
>More important: you still didn't explain how is your "no strings"
>approach supposed to work for bit sets where userspace cannot possibly
>know the set of available flags (e.g. the private flags).

I know, that is a different part of this thread.

>
>Michal