Re: [PATCH v2] ethdev: add Linux ethtool link mode conversion

[Thomas Monjalon <thomas@monjalon.net>]

01/03/2024 16:08, Ferruh Yigit:
> On 3/1/2024 1:37 PM, Thomas Monjalon wrote:
> > 01/03/2024 14:12, Ferruh Yigit:
> >> On 2/29/2024 3:42 PM, Thomas Monjalon wrote:
> >>> Speed capabilities of a NIC may be discovered through its Linux
> >>> kernel driver. It is especially useful for bifurcated drivers,
> >>> so they don't have to duplicate the same logic in the DPDK driver.
> >>>
> >>> Parsing ethtool speed capabilities is made easy thanks to
> >>> the functions added in ethdev for internal usage only.
> >>> Of course these functions work only on Linux,
> >>> so they are not compiled in other environments.
> >>>
> >>> In order to ease parsing, the ethtool macro names are parsed
> >>> externally in a shell command which generates a C array
> >>> included in this patch.
> >>> It also avoids to depend on a kernel version.
> >>> This C array should be updated in future to get latest ethtool bits.
> >>> Note it is easier to update this array than adding new cases
> >>> in a parsing code.
> >>>
> >>> The types in the functions are following the ethtool type:
> >>> uint32_t for bitmaps, and int8_t for the number of 32-bitmaps.
> >>>
> >>> Signed-off-by: Thomas Monjalon <thomas@monjalon.net>
> >>> ---
> >>>
> >>> A follow-up patch will be sent to use these functions in mlx5.
> >>> I suspect mana could use this parsing as well.
> >>>
> >>
> >> Is the usecase driver get link info via ibverbs and convert it to DPDK
> >> link info?
> > 
> > The use case is to get capabilities from the kernel driver via ethtool ioctl.
> > 
> 
> Sure, as it is adding kernel ethtool conversion, DPDK driver will get
> link from kernel driver, thanks for clarification.

Yes the PMD uses ethtool API to get device capabilies.

> >> How complex or duplicated effort to get link info directly via DPDK
> >> functions?
> > 
> > This is done by the driver.
> > This is how mlx5 driver is getting speed capabilities.
> > 
> >> Because this approach is can be applied to only limited devices in DPDK
> >> and solving an issue DPDK already has a solution, does it worth to the
> >> code it adds?
> > 
> > It is going to replace code in mlx5 driver.
> > I could add this code in mlx5 driver,
> > but it could help other drivers in future like mana.
> 
> Why replace, is there anything to fix in the DPDK link get code?

There is nothing to fix in ethdev layer.
I want to replace PMD code doing ethtool queries
with something cleaner and easier to update.