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Re: [PATCH 1/4] netdev/phy: Handle IEEE802.3 clause 45 Ethernet PHYs

To: David Miller <davem@davemloft.net>
Subject: Re: [PATCH 1/4] netdev/phy: Handle IEEE802.3 clause 45 Ethernet PHYs
From: David Daney <ddaney.cavm@gmail.com>
Date: Mon, 25 Jun 2012 16:11:23 -0700
Cc: grant.likely@secretlab.ca, rob.herring@calxeda.com, devicetree-discuss@lists.ozlabs.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mips@linux-mips.org, afleming@gmail.com, david.daney@cavium.com
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On 06/25/2012 03:34 PM, David Miller wrote:
From: David Daney<ddaney.cavm@gmail.com>
Date: Fri, 22 Jun 2012 17:24:13 -0700

From: David Daney<david.daney@cavium.com>

The IEEE802.3 clause 45 MDIO bus protocol allows for directly
addressing PHY registers using a 21 bit address, and is used by many
10G Ethernet PHYS.  Already existing is the ability of MDIO bus
drivers to use clause 45, with the MII_ADDR_C45 flag.  Here we add
struct phy_c45_device_ids to hold the device identifier registers
present in clause 45. struct phy_device gets a couple of new fields:
c45_ids to hold the identifiers and is_c45 to signal that it is clause
45.

Normally the MII_ADDR_C45 flag is ORed with the register address to
indicate a clause 45 transaction.  Here we also use this flag in the
*device* address passed to get_phy_device() to indicate that probing
should be done with clause 45 transactions.

EXPORT phy_device_create() so that the follow-on patch to of_mdio.c
can use it to create phy devices for PHYs, that have non-standard
device identifier registers, based on the device tree bindings.

Signed-off-by: David Daney<david.daney@cavium.com>

I see no value in having two ways to say that clause-45 transactions
should be used.

Either make it a PHY device attribute, or specify it in the address
in the register accesses, but not both.


Do you realize that at the time get_phy_device() is called, there is no PHY device? So there can be no attribute, nor are we passing a register address. Neither of these suggestions apply to this situation.

We need to know a priori if it is c22 or c45. So we need to communicate the type somehow to get_phy_device(). I chose an unused bit in the addr parameter to do this, another option would be to add a separate parameter to get_phy_device() specifying the type.



Also your patch is full of coding style errors, I simply couldn't
stomache applying this even if I agreed with the substance of the
changes:

+            i<  ARRAY_SIZE(c45_ids->device_ids)&&
+                    c45_ids->devices_in_package == 0;

c45_ids on the second line should line up with the initial 'i'
on the first line.

+               c45_ids->devices_in_package = (phy_reg&  0xffff)<<  16;
+
+
+               reg_addr = MII_ADDR_C45 | i<<  16 | 5;

There is not reason in the world to have two empty lines there, it
looks awful.

OK, I will fix those...


+               /*
+                * If mostly Fs, there is no device there,
+                * let's get out of here.
+                */

Format comments:

        /* Like
         * this.
         */

Not.

        /*
         * Like
         * this.
         */

... and this one too I guess. Really you and Linus should come to a consensus on this one.

[...]

+/*
+ * phy_c45_device_ids: 802.3-c45 Device Identifiers
+ *
+ * devices_in_package: Bit vector of devices present.
+ * device_ids: The device identifer for each present device.
+ */

If you're going to list the struct members use the correct kerneldoc
format to do so.

OK.

David Daney

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