netdev - Re: [PATCH v2 1/2] net: macb: Clean up macb

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Date:   Fri, 15 Oct 2021 18:28:10 -0400
From:   Sean Anderson <sean.anderson@...o.com>
To:     "Russell King (Oracle)" <linux@...linux.org.uk>
Cc:     Antoine Tenart <atenart@...nel.org>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org,
        Nicolas Ferre <nicolas.ferre@...rochip.com>,
        Claudiu Beznea <claudiu.beznea@...rochip.com>
Subject: Re: [PATCH v2 1/2] net: macb: Clean up macb_validate




On 10/14/21 7:08 PM, Russell King (Oracle) wrote:
> On Thu, Oct 14, 2021 at 01:50:36PM -0400, Sean Anderson wrote:
>> On 10/14/21 12:34 PM, Russell King (Oracle) wrote:
>> > You can find some patches that add the "supported_interfaces" masks
>> > in git.armlinux.org.uk/linux-arm.git net-queue
>> >
>> > and we could add to phylink_validate():
>> >
>> > 	if (!phy_interface_empty(pl->config->supported_interfaces) &&
>> > 	    !test_bit(state->interface, pl->config->supported_interfaces))
>> > 		return -EINVAL;
>> >
>> > which should go a long way to simplifying a lot of these validation
>> > implementations.
>> >
>> > Any thoughts on that?
>>
>> IMO the actual issue here is PHY_INTERFACE_MODE_NA. Supporting this
>> tends to add complexity to validate(), because we have a lot of code
>> like
>>
>> 	if (state->interface == PHY_INTERFACE_MODE_FOO) {
>> 		if (we_support_foo())
>> 			phylink_set(mask, Foo);
>> 		else if (state->interface != PHY_INTERFACE_MODE_NA) {
>> 			linkmode_zero(supported);
>> 			return;
>> 		}
>> 	}
>>
>> which gets even worse when we want to have different interfaces share
>> logic.
>
> There is always the option to use different operations structs if the
> properties of the interfaces can be divided up in that way - and that
> will probably be more efficient (not that the validate callback is a
> performance critical path though.)
>
>> IMO validate() could be much cleaner if we never called it with
>> NA and instead did something like
>>
>> 	if (state->interface == PHY_INTERFACE_MODE_NA) {
>> 		unsigned long *original;
>>
>> 		linkmode_copy(original, supported);
>> 		for (i = 0; i < PHY_INTERFACE_MODE_MAX; i++) {
>> 			if (test_bit(i, pl->config->supported_interfaces)) {
>> 				unsigned long *iface_mode;
>>
>> 				linkmode_copy(iface_mode, original);
>> 				state->interface = i;
>> 				pl->mac_ops->validate(pl->config, iface_mode, state);
>> 				linkmode_or(supported, supported, iface_mode);
>> 			}
>> 		}
>> 		state->interface = PHY_INTERFACE_MODE_NA;
>> 	}
>>
>> This of course can be done in addition to/instead of your above
>> suggestion. I suggested something like this in v3 of this series, but it
>> would be even better to do this on the phylink level.
>
> In addition I think - I think we should use a non-empty
> supported_interfaces as an indicator that we use the above, otherwise
> we have to loop through all possible interface modes. That also
> provides some encouragement to fill out the supported_interfaces
> member.

I had a stab at this today [1], but it is only compile-tested. In order
to compile "net: phylink: use phy_interface_t bitmaps for optical
modules", I needed to run

	sed -ie 's/sfp_link_an_mode/cfg_link_an_mode/g' drivers/net/phy/phylink.c

Do you plan on making up a series for this? I think the end result is
much nicer that v3 of this series.

--Sean

[1] https://github.com/sean-anderson-seco/linux/commits/supported_interfaces_wip