Subject: Re: [PATCH net-next] docs: netdev: refine netdevsim testing guidance

From: Simon Horman <[email-masked]>
Date: Fri, 6 Mar 2026 14:39:03 +0000

On Wed, Mar 04, 2026 at 07:16:46AM -0800, Jakub Kicinski wrote:
> The library to create tests for both NIC HW and netdevsim has existed
> for almost a year. netdevsim-only tests we get increasingly feel like
> a waste, we should try to write tests that work both on netdevsim and
> real HW. Refine the guidance accordingly.
> 
> Signed-off-by: Jakub Kicinski <[email-masked]>
> ---
> CC: [email-masked]
> CC: [email-masked]
> CC: [email-masked]
> CC: [email-masked]

Reviewed-by: Simon Horman <[email-masked]>

> ---
>  Documentation/process/maintainer-netdev.rst | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/Documentation/process/maintainer-netdev.rst b/Documentation/process/maintainer-netdev.rst
> index 6bce4507d5d3..3aa13bc2405d 100644
> --- a/Documentation/process/maintainer-netdev.rst
> +++ b/Documentation/process/maintainer-netdev.rst
> @@ -479,8 +479,14 @@ netdevsim
>  
>  ``netdevsim`` is a test driver which can be used to exercise driver
>  configuration APIs without requiring capable hardware.
> -Mock-ups and tests based on ``netdevsim`` are strongly encouraged when
> -adding new APIs, but ``netdevsim`` in itself is **not** considered
> +Mock-ups and tests based on ``netdevsim`` are encouraged when
> +adding new APIs with complex logic in the stack. The tests should
> +be written so that they can run both against ``netdevsim`` and a real
> +device (see ``tools/testing/selftests/drivers/net/README.rst``).
> +``netdevsim``-only tests should focus on testing corner cases
> +and failure paths in the core which are hard to exercise with a real driver.
> +
> +``netdevsim`` in itself is **not** considered
>  a use case/user. You must also implement the new APIs in a real driver.

I don't know if it's desirable, but the line wrapping could
also be updated.

>  
>  We give no guarantees that ``netdevsim`` won't change in the future
> -- 
> 2.53.0
>