netdev - Re: [PATCH net-next 01/15] sfc: support setting MTU even if not privileged to configure MAC fully

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Message-ID: <20200701120311.4821118c@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
Date:   Wed, 1 Jul 2020 12:03:11 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Edward Cree <ecree@...arflare.com>
Cc:     <linux-net-drivers@...arflare.com>, <davem@...emloft.net>,
        <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next 01/15] sfc: support setting MTU even if not
 privileged to configure MAC fully

On Wed, 1 Jul 2020 15:51:25 +0100 Edward Cree wrote:
> Unprivileged functions (such as VFs) may set their MTU by use of the
>  'control' field of MC_CMD_SET_MAC_EXT, as used in efx_mcdi_set_mtu().
> If calling efx_ef10_mac_reconfigure() from efx_change_mtu(), the NIC
>  supports the above (SET_MAC_ENHANCED capability), and regular
>  efx_mcdi_set_mac() fails EPERM, then fall back to efx_mcdi_set_mtu().

Is there no way of checking the permission the function has before
issuing the firmware call?