linux-kernel - Re: [PATCH v2] net: dsa: lan9303: add VLAN IDs to master device

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Date:   Sun, 20 Feb 2022 19:00:37 +0200
From:   Vladimir Oltean <olteanv@...il.com>
To:     Mans Rullgard <mans@...sr.com>
Cc:     Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Juergen Borleis <kernel@...gutronix.de>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] net: dsa: lan9303: add VLAN IDs to master device

On Thu, Feb 17, 2022 at 01:59:30AM +0200, Vladimir Oltean wrote:
> On Wed, Feb 16, 2022 at 08:48:18PM +0000, Mans Rullgard wrote:
> > If the master device does VLAN filtering, the IDs used by the switch
> > must be added for any frames to be received.  Do this in the
> > port_enable() function, and remove them in port_disable().
> > 
> > Signed-off-by: Mans Rullgard <mans@...sr.com>
> > ---
> 
> Reviewed-by: Vladimir Oltean <olteanv@...il.com>

There's a problem with this patch.

CONFIG_NET_DSA_SMSC_LAN9303 is not user-selectable, but it is selected
by CONFIG_NET_DSA_SMSC_LAN9303_I2C or CONFIG_NET_DSA_SMSC_LAN9303_MDIO.
The point is that config options that aren't user-selectable but are
automatically selected shouldn't have dependencies. AFAIK, the
dependencies should be transferred to the user-facing options
(_I2C and _MDIO).

What happens is that if you make CONFIG_VLAN_8021Q a module, you get
this warning:

WARNING: unmet direct dependencies detected for NET_DSA_SMSC_LAN9303
  Depends on [m]: NETDEVICES [=y] && NET_DSA [=y] && (VLAN_8021Q [=m] || VLAN_8021Q [=m]=n)
  Selected by [y]:
  - NET_DSA_SMSC_LAN9303_I2C [=y] && NETDEVICES [=y] && NET_DSA [=y] && I2C [=y]
  - NET_DSA_SMSC_LAN9303_MDIO [=y] && NETDEVICES [=y] && NET_DSA [=y]

The point of the dependency was to force the LAN9303 driver as a module
if 8021Q is a module, but this doesn't happen because the dependency
isn't where it should be.