Re: [PATCH] net/ixgbe: Treat 1G Cu SFPs as 1G SX on the X550 devices

[Thomas Monjalon <thomas@monjalon.net>]

14/04/2022 17:43, Stephen Hemminger:
> On Thu, 14 Apr 2022 15:11:46 +0000
> Jeff Daly <jeffd@silicom-usa.com> wrote:
> > From: Thomas Monjalon <thomas@monjalon.net>
> > > 14/04/2022 14:13, Wang, Haiyue:  
> > > > From: Thomas Monjalon <thomas@monjalon.net>  
> > > > > 14/04/2022 03:31, Wang, Haiyue:  
> > > > > > From: jeffd@silicom-usa.com <jeffd@silicom-usa.com>  
> > > > > > > From: Stephen Douthit <stephend@silicom-usa.com>
> > > > > > >
> > > > > > > 1G Cu SFPs are not officially supported on the X552/X553 family
> > > > > > > of devices but treat them as 1G SX modules since they usually
> > > > > > > work.  Print a warning though since support isn't validated,
> > > > > > > similar to what already happens for other unofficially supported
> > > > > > > SFPs enabled via the allow_unsupported_sfps parameter inherited  
> > > from the mainline Linux driver.  
> > > > > > >
> > > > > > > Signed-off-by: Stephen Douthit <stephend@silicom-usa.com>
> > > > > > > Signed-off-by: Jeff Daly <jeffd@silicom-usa.com>
> > > > > > > ---
> > > > > > >  drivers/net/ixgbe/base/ixgbe_x550.c | 14 +++++++++++++-
> > > > > > >  1 file changed, 13 insertions(+), 1 deletion(-)
> > > > > > >
> > > > > > > diff --git a/drivers/net/ixgbe/base/ixgbe_x550.c
> > > > > > > b/drivers/net/ixgbe/base/ixgbe_x550.c
> > > > > > > index 8810d1658e..8d1bc6c80d 100644
> > > > > > > --- a/drivers/net/ixgbe/base/ixgbe_x550.c
> > > > > > > +++ b/drivers/net/ixgbe/base/ixgbe_x550.c
> > > > > > > @@ -1538,9 +1538,21 @@ STATIC s32
> > > > > > > ixgbe_supported_sfp_modules_X550em(struct ixgbe_hw *hw, bool  
> > > > > *linear)  
> > > > > >
> > > > > > NACK.
> > > > > >
> > > > > > As for 1G Cu SFP treating it as 1G SX, some 1G-Base-T SFP modules
> > > > > > require the use of RX_ILOS and some Intel Ethernet products don't  
> > > support that.  
> > > > >
> > > > > So what is the solution?
> > > > >  
> > > > > > And the DPDK keeps the same design with kernel.  
> > > > >
> > > > > It should not be a justification for limiting DPDK features.  
> > > >
> > > > Um, this is upstream version driver to keep the same behavior.
> > > >
> > > > There are also some kind of custom release ...  
> > > 
> > > I don't understand.
> > > Upstream DPDK (and Linux) must support a maximum of hardware and
> > > setup.
> > > Why rejecting adding such compatibility?
> > >   
> > 
> > so, I will ask a question directly in case people just aren't inclined to make a suggestion
> > (and perhaps this should be also directed to the Linux kernel driver mailing list), but
> > if there's a driver option: module_param(allow_unsupported_sfp, uint, 0) to allow 
> > enabling non-official support of some SFPs, then I can't image that it wouldn't also be
> > acceptable to add: module_param(cu_sfp_as sx, uint, 0) to be able to select whether
> > to enable this specific handling as well?
> > 
> > if a patch of this nature is acceptable to Linux driver maintainers, then it would also be
> > here as well according to your explanation of the NACK,  correct?
> 
> Makes sense for DPDK to have a similar option to enable (at your own risk) SFP's.
> But: 
>    - there is no equivalent of module_params in DPDK; you will have to think of something

We have devargs which is supposed to be used per port with the option -a.
In future, I would like to use devargs with another option
which is not necessarily tight to a port, so it can be per-driver.
The devargs syntax already allows to configure a driver, example:
	class=eth/driver=foo,param=bar

>    - should print message that when enabled the driver is no longer supported.

It could be supported by Silicom.

>      use at your own risk.