Re: [PATCH iwl-next v5 9/9] igc: Block setting preemptible traffic class in taprio

[Vladimir Oltean]

On Wed, Feb 19, 2025 at 09:53:49PM -0500, Faizal Rahim wrote:
> Since preemptible tc implementation is not ready yet, block it from being
> set in taprio. The existing code already blocks it in mqprio.
> 
> Signed-off-by: Faizal Rahim <faizal.abdul.rahim@xxxxxxxxxxxxxxx>
> ---
>  drivers/net/ethernet/intel/igc/igc_main.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/net/ethernet/intel/igc/igc_main.c b/drivers/net/ethernet/intel/igc/igc_main.c
> index 5a6648a12a53..e6a398dbf09b 100644
> --- a/drivers/net/ethernet/intel/igc/igc_main.c
> +++ b/drivers/net/ethernet/intel/igc/igc_main.c
> @@ -6408,6 +6408,10 @@ static int igc_save_qbv_schedule(struct igc_adapter *adapter,
>  	if (!validate_schedule(adapter, qopt))
>  		return -EINVAL;
>  
> +	/* preemptible isn't supported yet */
> +	if (qopt->mqprio.preemptible_tcs)
> +		return -EOPNOTSUPP;
> +
>  	igc_ptp_read(adapter, &now);
>  
>  	if (igc_tsn_is_taprio_activated_by_user(adapter) &&
> -- 
> 2.34.1
>

This patch should be before the patch that makes ethtool_dev_mm_supported()
return true for igc, i.e. 7/9 "igc: Add support to get MAC Merge data via ethtool".
You don't want the kernel to be in a state at all where it accepts a
configuration it doesn't support, even if it's temporary and you're
fixing it up within the same patch set, because it may be visible during
e.g. a git bisect.