netdev - Re: [PATCH net-next v11 1/4] net netlink: Add new type NLA_BITFIELD

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Message-ID: <c492d995-a916-cbed-b545-8d110a6ffb1e@mojatatu.com>
Date:   Tue, 25 Jul 2017 07:15:52 -0400
From:   Jamal Hadi Salim <jhs@...atatu.com>
To:     Jiri Pirko <jiri@...nulli.us>
Cc:     davem@...emloft.net, netdev@...r.kernel.org,
        xiyou.wangcong@...il.com, dsahern@...il.com,
        eric.dumazet@...il.com, mrv@...atatu.com,
        simon.horman@...ronome.com, alex.aring@...il.com
Subject: Re: [PATCH net-next v11 1/4] net netlink: Add new type
 NLA_BITFIELD_32

On 17-07-24 07:18 AM, Jiri Pirko wrote:
> Mon, Jul 24, 2017 at 03:35:43AM CEST, jhs@...atatu.com wrote:
>> From: Jamal Hadi Salim <jhs@...atatu.com>
>>
>> Generic bitflags attribute content sent to the kernel by user.
>> With this type the user can either set or unset a flag in the
>> kernel.
>>
>> The nla_value is a bitmap that defines the values being set
>> The nla_selector is a bitmask that defines which value is legit.
>>
>> A check is made to ensure the rules that a kernel subsystem always
>> conforms to bitflags the kernel already knows about. i.e
>> if the user tries to set a bit flag that is not understood then
>> the _it will be rejected_.
>>
>> In the most basic form, the user specifies the attribute policy as:
>> [ATTR_GOO] = { .type = NLA_BITFIELD_32, .validation_data = &myvalidflags },
>>
>> where myvalidflags is the bit mask of the flags the kernel understands.
>>
>> If the user _does not_ provide myvalidflags then the attribute will
>> also be rejected.
>>
>> Examples:
>> nla_value = 0x0, and nla_selector = 0x1
>> implies we are selecting bit 1 and we want to set its value to 0.
>>
>> nla_value = 0x2, and nla_selector = 0x2
>> implies we are selecting bit 2 and we want to set its value to 1.
> 
> Oh, 2 more things:
> 
> [...]
> 

;-> ok will do that next opportunity (probably at 30K feet).

cheers,
jamal