netdev - Re: [PATCH V5] net: phy: tja11xx: Add TJA11xx PHY driver

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Date:   Sat, 18 May 2019 22:12:51 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Marek Vasut <marex@...x.de>
Cc:     netdev@...r.kernel.org, Florian Fainelli <f.fainelli@...il.com>,
        Guenter Roeck <linux@...ck-us.net>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Jean Delvare <jdelvare@...e.com>, linux-hwmon@...r.kernel.org
Subject: Re: [PATCH V5] net: phy: tja11xx: Add TJA11xx PHY driver

On Sat, May 18, 2019 at 06:50:48PM +0200, Marek Vasut wrote:
> On 5/18/19 4:14 PM, Andrew Lunn wrote:
> > On Sat, May 18, 2019 at 01:51:23AM +0200, Marek Vasut wrote:
> >> Add driver for the NXP TJA1100 and TJA1101 PHYs. These PHYs are special
> >> BroadRReach 100BaseT1 PHYs used in automotive.
> > 
> > Hi Marek
> 
> Hello Andrew,
> 
> >> +	}, {
> >> +		PHY_ID_MATCH_MODEL(PHY_ID_TJA1101),
> >> +		.name		= "NXP TJA1101",
> >> +		.features       = PHY_BASIC_T1_FEATURES,
> > 
> > One thing i would like to do before this patch goes in is define
> > ETHTOOL_LINK_MODE_100baseT1_Full_BIT in ethtool.h, and use it here.
> > We could not do it earlier because were ran out of bits. But with
> > PHYLIB now using bitmaps, rather than u32, we can.
> > 
> > Once net-next reopens i will submit a patch adding it.
> 
> I can understand blocking patches from being applied if they have review
> problems or need to be updated on some existing or even posted feature.
> But blocking a patch because some future yet-to-be-developed patch is a
> bit odd.

Hi Marek

What i'm trying to avoid is an ABI change. By using
PHY_BASIC_T1_FEATURES you are saying the device support 100BaseT. It
does not. It supports 100BaseT1. I want to add 100BaseT1 first, so
your PHY does not change from 100BaseT to 100BaseT1, which could be
considered an ABI change.

I'm not suggesting blocking your patch for a long time. I'm already
2/3 of the way doing the work. At the latest, i expect to have patches
submitted in the next few days. And then your driver can go in, using
this. So by end of next week, your driver can be in.

> > I also see in the data sheet we should be able to correct detect its
> > features using register 15. So we should extend
> > genphy_read_abilities().
> 
> Which bits do you refer to ?

Register 15, bit 7. This indicates the PHY can do 100BaseT1. I want to
double check with the 802.3 standard, but i expect this is part of the
standard.

	Andrew