linux-kernel - Re: [PATCH 01/20] net: phy: realtek: Fix events detection failure in LPI mode

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Message-ID: <20210209105455.GO1463@shell.armlinux.org.uk>
Date:   Tue, 9 Feb 2021 10:54:55 +0000
From:   Russell King - ARM Linux admin <linux@...linux.org.uk>
To:     Serge Semin <Sergey.Semin@...kalelectronics.ru>
Cc:     Heiner Kallweit <hkallweit1@...il.com>,
        Serge Semin <fancer.lancer@...il.com>,
        Giuseppe Cavallaro <peppe.cavallaro@...com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        Jose Abreu <joabreu@...opsys.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Joao Pinto <Joao.Pinto@...opsys.com>,
        Jose Abreu <Jose.Abreu@...opsys.com>,
        Andrew Lunn <andrew@...n.ch>,
        Alexey Malahov <Alexey.Malahov@...kalelectronics.ru>,
        Pavel Parkhomenko <Pavel.Parkhomenko@...kalelectronics.ru>,
        Vyacheslav Mitrofanov 
        <Vyacheslav.Mitrofanov@...kalelectronics.ru>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        netdev@...r.kernel.org, linux-stm32@...md-mailman.stormreply.com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 01/20] net: phy: realtek: Fix events detection failure in
 LPI mode

On Tue, Feb 09, 2021 at 01:15:28PM +0300, Serge Semin wrote:
> On Mon, Feb 08, 2021 at 09:14:02PM +0100, Heiner Kallweit wrote:
> > Nice analysis. Alternatively to duplicating this code piece we could
> > export mmd_phy_indirect(). But up to you.
> 
> I also considered creating a generic method to access the MMD
> registers of a generic PHY, something like phy_read()/phy_write(), but
> for MMD (alas just exporting mmd_phy_indirect() would not be enough).
> But as I see it such methods need to be created only after we get to
> have at least several places with duplicating direct MMD-read/write
> patterns. Doing that just for a single place seems redundant. Anyway it's
> up to maintainers to decide whether they want to see a generic part
> of the phy_read_mmd()/phy_write_mmd() methods being detached and
> exported as something like genphy_{read,write}_mmd() methods. I can do
> that in v2 if you ask me to.

Please not genphy_* - that namespace is used for up-to-1G PHYs.

I thought about suggesting what you are proposing, but the problem is
this is just making things less and less efficient. Every time we
break a function up and export it, we increase the execution overhead
of the code. That said, the PHY accesses are relatively slow.

My opinion is that as this is just a single location at the moment,
it is not worth the effort - but if we get more of examples of this,
then it makes sense to provide the common accessor.

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