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From: Florian Fainelli <f.fainelli@gmail.com>
To: Mike Looijmans <mike.looijmans@topic.nl>, Andrew Lunn <andrew@lunn.ch>
Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
	devicetree@vger.kernel.org, robh+dt@kernel.org,
	frowand.list@gmail.com
Subject: Re: [PATCH] of_net: Implement of_get_nvmem_mac_address helper
Date: Fri, 23 Mar 2018 12:33:41 -0700	[thread overview]
Message-ID: <886c94ef-e2c8-2afa-307d-1924c74c6dc0@gmail.com> (raw)
In-Reply-To: <b68d4540-b15d-ec31-05a8-e1a4632bb5ee@topic.nl>

On 03/23/2018 12:20 PM, Mike Looijmans wrote:
> On 23-3-2018 16:11, Andrew Lunn wrote:
>> On Fri, Mar 23, 2018 at 03:24:34PM +0100, Mike Looijmans wrote:
>>> It's common practice to store MAC addresses for network interfaces into
>>> nvmem devices. However the code to actually do this in the kernel lacks,
>>> so this patch adds of_get_nvmem_mac_address() for drivers to obtain the
>>> address from an nvmem cell provider.
>>>
>>> This is particulary useful on devices where the ethernet interface
>>> cannot
>>> be configured by the bootloader, for example because it's in an FPGA.
>>>
>>> Tested by adapting the cadence macb driver to call this instead of
>>> of_get_mac_address().
>>
>> Hi Mike
>>
>> Please can you document the device tree binding. I assume you are
>> adding a nvmen-cells and nvmem-cell-names to the Ethernet node in
>> device tree.
> 
> Indeed. I'll add my settings as an example. Where should I put this
> documentation, in the commit comment or somewhere in
> Documents/devicetree/bindings?
> 
>>> +/**
>>> + * Search the device tree for a MAC address, by calling
>>> of_get_mac_address
>>> + * and if that doesn't provide an address, fetch it from an nvmem
>>> provider
>>> + * using the name 'mac-address'.
>>> + * On success, copies the new address is into memory pointed to by
>>> addr and
>>> + * returns 0. Returns a negative error code otherwise.
>>> + * @dev:    Pointer to the device containing the device_node
>>> + * @addr:    Pointer to receive the MAC address using ether_addr_copy()
>>> + */
>>> +int of_get_nvmem_mac_address(struct device *dev, char *addr)
>>> +{
>>> +    const char *mac;
>>> +    struct nvmem_cell *cell;
>>> +    size_t len;
>>> +    int ret;
>>> +
>>> +    mac = of_get_mac_address(dev->of_node);
>>> +    if (mac) {
>>> +        ether_addr_copy(addr, mac);
>>> +        return 0;
>>> +    }
>>
>> Is there a need to add a new API? Could of_get_mac_address() be
>> extended to look in NVMEM? The MAC driver does not care. It is saying,
>> using OF get me a MAC address. One API seems sufficient, and would
>> mean you don't need to change the MAC drivers.
> 
> It's what I intended to do, but there were two problems with that:
> - of_get_mac_address() returns a pointer to constant data in memory, but
> the nvmem functions return an allocated memory object that must be freed
> after use. This changes the way the call is to be made.

Yeah...

> - The nvmem functions need the "struct device" pointer as well, while
> of_get_mac_address() only gets passed the DT node.

Bummer, you can't assume there is always a struct device associated with
a struct device_node. Also, bigger question is, how can we make this
work, for e.g: ACPI systems and therefore use an abstract fw_node handle?

> 
> One approach would be to deprecate the of_get_mac_address() interface
> and migrate existing drivers to the of_get_nvmem_mac_address() interface.

Humm maybe, but clearly making of_get_mac_address() look for a nvmem is
less error prone and does not require people to opt-in for the new
helper, that seems beneficial to me.
-- 
Florian

  reply	other threads:[~2018-03-23 19:33 UTC|newest]

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-03-23 14:24 [PATCH] of_net: Implement of_get_nvmem_mac_address helper Mike Looijmans
2018-03-23 15:11 ` Andrew Lunn
2018-03-23 19:20   ` Mike Looijmans
2018-03-23 19:33     ` Florian Fainelli [this message]
2018-03-24 16:17       ` Mike Looijmans
2018-03-24 18:53         ` Andrew Lunn
2018-03-25  8:17           ` Mike Looijmans
2018-03-25 21:04             ` Andrew Lunn
2018-03-26  6:54             ` Mike Looijmans
2018-03-23 19:42     ` Andrew Lunn
2018-03-24 16:03       ` Mike Looijmans
2018-03-26  6:41   ` [PATCH v2] " Mike Looijmans
2018-03-26 15:50     ` Andrew Lunn
2018-03-26 18:25       ` Mike Looijmans
2018-03-26 18:41         ` Andrew Lunn
2018-03-26 16:58     ` David Miller
2018-03-26 17:05       ` Florian Fainelli
2018-03-26 18:21         ` Mike Looijmans
2018-03-27  9:52     ` [PATCH v3 0/2] " Mike Looijmans
2018-03-27  9:52       ` [PATCH v3 1/2] " Mike Looijmans
2018-03-27 22:50         ` Florian Fainelli
2018-03-29  5:31           ` Mike Looijmans
2018-03-27  9:52       ` [PATCH v3 2/2] net: macb: Try to retrieve MAC addess from nvmem provider Mike Looijmans
2018-03-28  8:00         ` Nicolas Ferre
2018-03-27 22:43       ` [PATCH v3 0/2] of_net: Implement of_get_nvmem_mac_address helper Andrew Lunn
2018-03-29  5:29       ` [PATCH v4 " Mike Looijmans
2018-03-29  5:29         ` [PATCH v4 1/2] " Mike Looijmans
2018-03-29  5:29         ` [PATCH v4 2/2] net: macb: Try to retrieve MAC addess from nvmem provider Mike Looijmans
2018-03-30 14:40         ` [PATCH v4 0/2] of_net: Implement of_get_nvmem_mac_address helper David Miller
2018-03-31 17:20           ` Mike Looijmans
2018-03-31 17:27             ` Andrew Lunn

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