Hi,

Grant Likely writes:

On Fri, 16 Mar 2012 11:01:35 +0800, Dong Aisheng [off-list ref] wrote:

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On Thu, Mar 15, 2012 at 07:22:04PM +0800, Lothar Waßmann wrote:

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Hi,

Dong Aisheng writes:

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On Thu, Mar 15, 2012 at 02:53:29PM +0800, Lothar Waßmann wrote:

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Hi,

Dong Aisheng writes:

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On Wed, Mar 14, 2012 at 10:16:43PM +0800, s.hauer@pengutronix.de wrote:

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On Wed, Mar 14, 2012 at 08:45:23PM +0800, Dong Aisheng wrote:

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On Wed, Mar 14, 2012 at 01:23:51AM +0800, Grant Likely wrote:

[...]

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But it seems this needs pass mac address to fec driver via platforom data which is
not friendly to dt.

Another way may be changing fec driver to get the fixed part of mac address(first
two bytes) from device tree and read the left dynamical part from otp which i'm not
sure is better enough.

BTW, filling with zeros seems not work since it's invalid mac address.

Yes, that's the idea of using this value...

But comparing to use an invalid value, why not just do not define that
local-mac-address property?

Because a MAC address is by definition a GLOBALLY UNIQUE IDENTIFIER
which is contrary to coding a "valid" default value for it somewhere!
The owner of a certain MAC address range (OUI) is responsible for
ensuring the uniqueness. Thus only they may assign a specific MAC
address to a specific device.

Yes, you're correct.
So i propose to read the MAC address from MX28 OTP in fec driver instead of
define it in device tree in my last mail.
http://www.spinics.net/lists/arm-kernel/msg165040.html
Do you have any comment on that way?

That patch sets the OUI to the Freescale owned MAC range. Thus only
Freescale products may be able to use the driver.

No.
My proposal is only set the fixed part(first two octets) in board dts file,
each board knows it's value, and read the left 4 octets from OCOTP dynamically.
Obviously the freeescale board dts file is only for FSL platforms.
Other platforms can define their fix part of MAC address in their dts file.

quoted

Anyway there is no definite spec how the MAC address(es) are stored
in the fuse map. Thus reading the MAC from there is more or less
platform specific.

It's just provide one more option since there are customers storing the MAC
in the fuse map.

That should be straight forward to support; have a property that
specifies the method used for fetching/calculating the MAC.

Executable code stored inside a DT blob? ;)

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Currently I'm setting up the MAC address for our TX28 from the fuses
in the platform code passed via platform_data, but that will obviously
not work with DT.

Non-dt can also use my proposal, then you only need to pass the fixed part of
MAC via platfrom data, the left will be read by fec driver.

quoted

The correct way would probably be to pass the MAC from the bootloader
via a DT blob. But that would require all bootloaders to be updated
first to support DTS. :(

But uboot will face the same problem that can not define a valid MAC
in dts, did i undertand correctly?

quoted

An intermediate solution could be using OF_DEV_AUXDATA to pass a
platform_data struct that may contain a MAC address set up by the
platform code.

Yes, it's a way but i'm afraid will not get accepted by dt people.

The problem remains; where does the platform code get the MAC address
from?  The kernel has to devise it from *somewhere* and the best place
for that should be in the MAC driver itself.

The platform code knows how and where the MAC is stored on a specific
platform. The driver has no business in knowing platform details like
this. Thus only platform code (or the bootloader) can provide the MAC
to the driver.

I've got no problem with the idea of only specifying the OUI in the DT
and the driver extracting the remaining 3 bytes from the hardware.

In principle, that's the design intent for DT systems anyway; it
describes things which cannot be probed from the hardware, or tells
the OS how the data is encoded in the hardware.

If all bootloaders were aware of DT this wouldn't be a problem,
because they could place the correct MAC inside the DT blob right
away.
But in the mean time (AKA forever) we need some other solution.


Lothar Waßmann
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