Date: Mon, 16 Jun 2014 11:01:18 +0200
From: Jiri Pirko <jiri@resnulli.us>
To: David Miller <davem@davemloft.net>
Cc: mprivozn@redhat.com, gregkh@linuxfoundation.org,
        linux-kernel@vger.kernel.org, netdev@vger.kernel.org
Subject: Re: [PATCH] net-sysfs: Report link speed only when possible
Message-ID: <20140616090118.GB3085@minipsycho.orion>
References: <539E9D93.9040405@redhat.com>
 <20140616.011148.2001285440663327901.davem@davemloft.net>
 <539EAB23.3020101@redhat.com>
 <20140616.014430.163976160998454211.davem@davemloft.net>
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Mon, Jun 16, 2014 at 10:44:30AM CEST, davem@davemloft.net wrote:
>From: Michal Privoznik <mprivozn@redhat.com>
>Date: Mon, 16 Jun 2014 10:30:27 +0200
>
>> On 16.06.2014 10:11, David Miller wrote:
>>> From: Michal Privoznik <mprivozn@redhat.com>
>>> Date: Mon, 16 Jun 2014 09:32:35 +0200
>>>
>>>> On 13.06.2014 22:03, David Miller wrote:
>>>>> From: Michal Privoznik <mprivozn@redhat.com>
>>>>> Date: Fri, 13 Jun 2014 11:19:51 +0200
>>>>>
>>>>>> So if I were developing brand new application I could say: I'm
>>>>>> dropping all this workaround code and have it clean and require say
>>>>>> 3.16 kernel at least.
>>>>>
>>>>> Then your application wouldn't be usable on %99 of systems for a long
>>>>> long time.
>>>>>
>>>>
>>>> How come? The application is going to be usable for as long as
>>>> library/kernel APIs won't change.
>>>
>>> Because %99 of users are using a distribution kernel which is
>>> definitely
>>> going to be pre-3.16 for years.
>>>
>> 
>> That's why every distribution out there has a mechanism to install
>> packages of a certain version, or those providing certain symbol,
>> whatever. Or distributions can then backport some kernel patches or
>> something. But, that's completely unrelated to the problem I'm fixing
>> here. I don't think this bikeshedding is useful for anything, sorry.
>
>You're being entirely impractical.
>
>By restricting an application to a kernel version or behavior "via
>backported patches" which doesn't even exist yet, you are foolishly
>restricting your userbase.
>
>People just cope with what the current kernels support, when possible,
>and that's the right thing to do because we cannot break it on them
>exactly because people can depend upon the behavior.
>
>NOBODY is checking for -EINVAL returns when reading the link speed
>sysfs file, and therefore by signalling it you will break
>applications.
>
>So I will not apply a patch which adds that new behavior, sorry.
>
>I am not willing to discuss this further, this is fundamental and
>simple as far as I'm concerned.
>

Let's just hope we do not introduce some other, more serious bug
somewhere else in user api. I see that such things are unfixable :/
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