netdev - Re: [PATCH 7/7] mlx5: Do not build eswitch_offloads if CONFIG_MLX5_EN_ESWITCH

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Date:   Sun, 4 Jun 2017 01:06:12 +0300
From:   Saeed Mahameed <saeedm@....mellanox.co.il>
To:     Or Gerlitz <gerlitz.or@...il.com>
Cc:     Jes Sorensen <jsorensen@...com>,
        Jes Sorensen <jes.sorensen@...il.com>,
        Linux Netdev List <netdev@...r.kernel.org>,
        Kernel Team <kernel-team@...com>,
        Saeed Mahameed <saeedm@...lanox.com>,
        Ilan Tayari <ilant@...lanox.com>
Subject: Re: [PATCH 7/7] mlx5: Do not build eswitch_offloads if
 CONFIG_MLX5_EN_ESWITCH_OFFLOADS is set

On Sat, Jun 3, 2017 at 10:37 PM, Or Gerlitz <gerlitz.or@...il.com> wrote:
> On Fri, Jun 2, 2017 at 11:22 PM, Jes Sorensen <jsorensen@...com> wrote:
>> On 05/28/2017 02:03 AM, Or Gerlitz wrote:
>>>
>>> On Sun, May 28, 2017 at 5:23 AM, Jes Sorensen <jes.sorensen@...il.com>
>>> wrote:
>>>>
>>>> On 05/27/2017 05:02 PM, Or Gerlitz wrote:
>>>>>
>>>>>
>>>>> On Sat, May 27, 2017 at 12:16 AM, Jes Sorensen <jes.sorensen@...il.com>
>>>>> wrote:
>>>>>>
>>>>>>
>>>>>> This gets rid of the temporary #ifdef spaghetti and allows the code to
>>>>>> compile without offload support enabled.
>>>
>>>
>>>>> I am pretty sure we can do that exercise you're up to without any
>>>>> spaghetti cooking and even put more code under that CONFIG directive
>>>>> (en_rep.c), I'll take that with Saeed.
>>>
>>>
>>>> I want to avoid adding #ifdef CONFIG_foo to the main code in order to
>>>> keep
>>>> it readable. I did it gradually to make sure I didn't break anything and
>>>> to
>>>> allow for it to be bisected in case something did break. If we can move
>>>> out
>>>> more code from places like en_rep.c into eswitch_offload.c and get it
>>>> disabled that way that would be great, but I like to limit the number of
>>>> #ifdefs we add to the actual code.
>>>
>>>
>>> FWIW (see below), squashing your seven patches to one resulted in a
>>> fairly simple/clear
>>> patch, so if we go that way, no need to have seven commits just for this
>>> piece.
>>
>>
>> Squashing patches into jumbo patches is inherently broken and bad coding
>> practice! It makes it way more complicated to debug and bisect in case a
>> minor detail broke in the process.
>
> Not that pure LOC ##-s is the only/deep measurement, but your overall
> changes in the the seven patch series account to:
>
>  5 files changed, 94 insertions(+), 3 deletions(-)
>
> and by no mean this is jumbo or inherently broken and bad coded, so
> please slow down please, I looked with care on the resulted patch and
> said it's basically ok.
>
>
>>> Re SRIOV, I don't think it would be correct to break the support info few
>>> CONFIG directives. If we want to allow someone to build the driver w.o
>>> SRIOV that's fine, but I don't think we should further go down and disable
>>> some of the SRIOV sub-modes.
>
>>> Re TC offload support, that's make sense.
>
>> OK, so disabling SRIOV and disabling TC makes sense - I'll look at that.
>
> I think Saeed wants us to conduct that exercise, let me check with him
> and get back to you

disabling SRIOV in all the kernel can do the trick, but we want
something more flexible, yet simple.
eswitch is required __ONLY__ for SRIOV, in the light of that fact we
can have CONFIG_MLX5_SRIOV which depends on kernel SRIOV
kconfig directive, that will eliminate  MLX5 sriov support (basically
compile out sriov.c, eswitch.c, eswitch_offloads.c and en_rep.c).

and stub out some sriov NDOs and some little API calls from the main
flows to the above mlx5 sub-modules.
Also we will need to compile out some en_tc.c offloads which meant to
program the eswitch they also call the eswitch_offloads API.