linux-kernel - Re: [PATCH] net: mdio-octeon: Add PCI driver binding.

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Message-Id: <20150924.151451.1059470233561232912.davem@davemloft.net>
Date:	Thu, 24 Sep 2015 15:14:51 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	ddaney@...iumnetworks.com
Cc:	ddaney.cavm@...il.com, linux-kernel@...r.kernel.org,
	robh+dt@...nel.org, pawel.moll@....com, mark.rutland@....com,
	ijc+devicetree@...lion.org.uk, galak@...eaurora.org,
	devicetree@...r.kernel.org, f.fainelli@...il.com,
	netdev@...r.kernel.org, david.daney@...ium.com
Subject: Re: [PATCH] net: mdio-octeon: Add PCI driver binding.

From: David Daney <ddaney@...iumnetworks.com>
Date: Thu, 24 Sep 2015 15:04:23 -0700

> On 09/24/2015 02:52 PM, David Miller wrote:
>> From: David Daney <ddaney.cavm@...il.com>
>> Date: Tue, 22 Sep 2015 17:41:36 -0700
>>
>>> From: David Daney <david.daney@...ium.com>
>>>
>>> When the Cavium mdio-octeon devices appear in the Thunder family of
>>> arm64 based SoCs, they show up as PCI devices.  Add PCI driver
>>> wrapping so the driver is bound in the standard PCI device scan.
>>>
>>> When in this form, a single PCI device may have more than a single
>>> bus, we call this a "nexus" of buses.  The standard firmware
>>> device_for_each_child_node() iterator is used to find the individual
>>> buses underneath the "nexus".
>>>
>>> Update the device tree binding documentation for the new PCI driver
>>> binding.
>>>
>>> Signed-off-by: David Daney <david.daney@...ium.com>
>>
>> This patch breaks the build:
> 
> For which architecture?
> 
> I tested it on mips and arm64.  I will try x86, as I guess that is
> where you tried your test build.

x86-64.

> There is, somewhat of, a method behind the madness here.
> 
> In order to use MSI-X interrupts, we need a corresponding PCI
> device. Now, this driver doesn't currently use interrupts, but other
> devices in the SoC do, so they must be PCI devices.

"I need this thing, which isn't needed, therefore I'm making this
change."

Sorry, that's not a good argument.

ACPI nodes have names and whatnot as well.

So I haven't heard a compelling argument so far.

So why not just implement this cleanly and using the existing
framework now, and then when you have a legitimate reason for making a
major change to the probing scheme you can do it then.
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