Re: [dpdk-stable] [PATCH v2] net/mlx5: fix link status query

[Adrien Mazarguil <adrien.mazarguil@6wind.com>]

On Wed, Feb 01, 2017 at 11:13:59AM +0000, Ferruh Yigit wrote:
> On 2/1/2017 9:07 AM, Adrien Mazarguil wrote:
> > On Wed, Feb 01, 2017 at 06:53:55AM +0000, Shahaf Shuler wrote:
> >> : Tuesday, January 31, 2017 6:17 PM, Ferruh Yigit:
> >>> On 1/31/2017 11:45 AM, Shahaf Shuler wrote:
> >>>> Trying to query the link status through new kernel ioctl API
> >>>> ETHTOOL_GLINKSETTINGS was always failing due to kernel bug.
> >>>> The bug was fixed on version 4.9
> >>>> this patch uses the legacy ioctl API for lower kernels.
> >>>>
> >>>> Fixes: 188408719888 ("net/mlx5: fix support for newer link speeds")
> >>>> CC: stable@dpdk.org
> >>>>
> >>>> Signed-off-by: Shahaf Shuler <shahafs@mellanox.com>
> >>>> ---
> >>>
> >>> <...>
> >>>
> >>>> @@ -707,7 +708,7 @@ struct priv *
> >>>>  static int
> >>>>  mlx5_link_update_unlocked_gs(struct rte_eth_dev *dev, int
> >>>> wait_to_complete)  { -#ifdef ETHTOOL_GLINKSETTINGS
> >>>> +#if KERNEL_VERSION(4, 9, 0) <= LINUX_VERSION_CODE
> >>>
> >>> Mostly it is not good idea to do kernel version check in the .c file.
> >>>
> >>> It is possible to move this comparison to the .h file, and set a feature
> >>> macro based on comparison result, like HAVE_ETHTOOL_GLINKSETTINGS,
> >>> and
> >>> use this macro in the .c file.
> >>>
> >>> This makes .c code easier to understand. And the abstraction in the
> >>> header file lets you update the comparison in the future without
> >>> changing the code itself.
> >>>
> >>> But it is your call, do you prefer to continue with this one?
> >>
> >> This is a good suggestion. 
> >> Adrien, Nélio what do you think?
> > 
> > Let's include this patch as-is. Doing so in a header file such as mlx5.h
> > would require including linux/version.h from that file and cause the entire
> > PMD to be even more OS-dependent.
> > 
> > We'll move this check elsewhere in the future if we need several such
> > workarounds, thanks.
> 
> OK.
> 
> One more thing, comment log says:
> "The bug was fixed on version 4.9"
> 
> And code does:
> "+#if KERNEL_VERSION(4, 9, 0) <= LINUX_VERSION_CODE"
>
> If the bug is fixed in 4.9, should check be "<" instead of "<="

I'll concede the argument order used in this condition is somewhat unusual
but it actually ends up being the same as:

 #if LINUX_VERSION_CODE > KERNEL_VERSION(4, 9, 0)

Which is the correct intent. I guess you can update this line for clarity if
you think it's necessary.

> > 
> >>>>  	struct priv *priv = mlx5_get_priv(dev);
> >>>>  	struct ethtool_link_settings edata = {
> >>>>  		.cmd = ETHTOOL_GLINKSETTINGS,
> >>> <...>
> > 
> 

-- 
Adrien Mazarguil
6WIND