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

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Date:   Thu, 14 Oct 2021 17:34:27 +0100
From:   "Russell King (Oracle)" <linux@...linux.org.uk>
To:     Antoine Tenart <atenart@...nel.org>
Cc:     "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Sean Anderson <sean.anderson@...o.com>, 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 Tue, Oct 12, 2021 at 10:33:04AM +0200, Antoine Tenart wrote:
> Hello Sean,
> 
> Quoting Sean Anderson (2021-10-11 18:55:16)
> > As the number of interfaces grows, the number of if statements grows
> > ever more unweildy. Clean everything up a bit by using a switch
> > statement. No functional change intended.
> 
> I'm not 100% convinced this makes macb_validate more readable: there are
> lots of conditions, and jumps, in the switch.
> 
> Maybe you could try a mixed approach; keeping the invalid modes checks
> (bitmap_zero) at the beginning and once we know the mode is valid using
> a switch statement. That might make it easier to read as this should
> remove lots of conditionals. (We'll still have the one/_NA checks
> though).

Some of this could be improved if we add the ability for a MAC to
specify the phy_interface_t modes that it supports as a bitmap
before calling phylink_create() - then we can have phylink check
that the mode is supported itself prior to calling the validate
handler.

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?

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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