From mboxrd@z Thu Jan  1 00:00:00 1970
From: Stephen Hemminger <stephen@networkplumber.org>
Subject: Re: DPDK drivers should not use kernel version
Date: Fri, 23 Jun 2017 10:55:22 -0700
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 <4376741f-cece-8086-eddb-c35ee9ef06a4@nxp.com>
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Cc: Shahaf Shuler <shahafs@mellanox.com>, Pascal Mazon
 <pascal.mazon@6wind.com>, <dev@dpdk.org>
To: Hemant Agrawal <hemant.agrawal@nxp.com>
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On Fri, 23 Jun 2017 13:03:55 +0530
Hemant Agrawal <hemant.agrawal@nxp.com> wrote:

> On 6/21/2017 9:58 PM, Stephen Hemminger wrote:
> > Looking at some other issues, I noticed that both the TAP and MLX5 device
> > drivers are looking at kernel version through uname.  Although this may
> > seem like a good way to deal with kernel API changes, it is not reliable.
> >
> > Enterprise kernel distro vendors never change kernel version but do backport
> > features from later kernels. Therefore the behavior expected may change
> > even though kernel version doesn't change. Also kernel version does not
> > dictate that the expected feature (like flower) is in the kernel configuration.
> >
> > I recommend this be looked for in all future submissions. Maybe even flagged
> > as error in DPDK version of checkpatch.  
> 
> what is the alternative than?
> 
> There are many legitimate cases, where userspace code need to make 
> decision on the basis underlying kernel version.
> 
> In some cases, user space code can add error handling and fallback, but 
> it is not possible in all cases.

Userspace code should test for the specific feature it wants. I.e
is the flow qdisc available.  Then report missing feature as error if
necessary.