linux-kernel - Re: [PATCH 4/6] of: add API for changing parameters of fixed link

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Date:	Fri, 27 Mar 2015 10:15:54 -0700
From:	Florian Fainelli <f.fainelli@...il.com>
To:	Stas Sergeev <stsp@...t.ru>
CC:	netdev <netdev@...r.kernel.org>,
	Linux kernel <linux-kernel@...r.kernel.org>,
	Stas Sergeev <stsp@...rs.sourceforge.net>,
	Grant Likely <grant.likely@...aro.org>,
	Rob Herring <robh+dt@...nel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
	Andrew Lunn <andrew@...n.ch>
Subject: Re: [PATCH 4/6] of: add API for changing parameters of fixed link

On 27/03/15 09:39, Stas Sergeev wrote:
> 27.03.2015 19:21, Florian Fainelli пишет:
>>> Do you want mvneta to register a similar callback in of_mdio, instead
>>> of adding an explicit state-updating functions? Something like
>>> of_phy_fixed_link_set_update_callback()?
>> You don't need an of_phy_fixed_link_set_update callback, you just need
>> to provide a fixed_link_update callback in mvneta, that you register,
> That approach I in fact considered initially, as the simplest one,
> and even had a patch. But I disliked the fact that then mvneta will
> exploit the knowledge of the fact that of_phy_register_fixed_link()
> uses a fixed_phy driver. What if the implementation will later change?

There is no reason why it should change later, that's the entire purpose
of why we can tell whether it is a fixed PHY or a regular MDIO-managed
PHY, and drivers rely on that for their operations.

> Also what makes me uncomfortable is that since of_phy_register_fixed_link()
> doesn't even return the struct phy_device pointer, mvneta will have
> to get around that and use for example of_phy_find_device(), or register
> the callback later, after of_phy_connect()

Ok, you could either make of_phy_register_fixed_link() return a
phy_device, or as you suggest resolve the phy_device from the
device_node later, your call.

. dsa/slave.c does of_phy_connect()
> initially, together with fixed link registration, so it gets around the
> problem. But mvneta registers the fixed_link in .probe callback, and
> does of_phy_connect() in .open callback.
> This all made me to drop that idea despite the simplicity.

Yet that's still the cleanest/less invasive approach imho.

> 
>>> This will remove a few changes indeed, but perhaps not too much.
>>> Please confirm if this is exactly what you want, and then I try.
>> Let me know if this is clearer now, if not, I can certainly cook a
>> patch which does what I am suggesting. Thanks!
> I can do that too, because I already did.
> Let me know if the above concerns are not important, and I'll
> restore my initial patch.
> 

I think your concerns are valid, but I don't think there is going to be
any problem with the approach I suggested because there is a contract
that the fixed PHYs and regular PHYs need to
-- 
Florian
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