Subject: Re: [PATCH net-next v2] ethtool: Clarify len/n_stats fields in/out semantics

From: Jakub Kicinski <[email-masked]>
Date: Tue, 13 Jan 2026 19:06:52 -0800

On Mon, 12 Jan 2026 13:57:08 +0200 Gal Pressman wrote:
> --- a/include/uapi/linux/ethtool.h
> +++ b/include/uapi/linux/ethtool.h
> @@ -1101,6 +1101,13 @@ enum ethtool_module_fw_flash_status {
>   * Users must use %ETHTOOL_GSSET_INFO to find the number of strings in
>   * the string set.  They must allocate a buffer of the appropriate
>   * size immediately following this structure.
> + *
> + * Setting @len on input is optional (though preferred), but must be zeroed
> + * otherwise.
> + * When set, @len will return the requested count if it matches the actual
> + * count; otherwise, it will be zero.
> + * This prevents issues when the number of strings is different than the
> + * userspace allocation.

Thanks the new text looks good, but we should also remove the 
"On return, the " from the field kdoc?