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From:   Bartosz Golaszewski <brgl@bgdev.pl>
Date:   Thu, 19 Jul 2018 17:07:40 +0200
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Subject: Re: [PATCH 5/5] net: add MTD support to eth_platform_get_mac_address()
To:     Andrew Lunn <andrew@lunn.ch>
Cc:     Sekhar Nori <nsekhar@ti.com>, Kevin Hilman <khilman@kernel.org>,
        Russell King <linux@armlinux.org.uk>,
        Grygorii Strashko <grygorii.strashko@ti.com>,
        "David S . Miller" <davem@davemloft.net>,
        Srinivas Kandagatla <srinivas.kandagatla@linaro.org>,
        Lukas Wunner <lukas@wunner.de>, Rob Herring <robh@kernel.org>,
        Florian Fainelli <f.fainelli@gmail.com>,
        Dan Carpenter <dan.carpenter@oracle.com>,
        Ivan Khoronzhuk <ivan.khoronzhuk@linaro.org>,
        David Lechner <david@lechnology.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Linux-OMAP <linux-omap@vger.kernel.org>, netdev@vger.kernel.org,
        Bartosz Golaszewski <bgolaszewski@baylibre.com>
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2018-07-19 17:01 GMT+02:00 Andrew Lunn <andrew@lunn.ch>:
> On Thu, Jul 19, 2018 at 10:14:29AM +0200, Bartosz Golaszewski wrote:
>> 2018-07-18 19:03 GMT+02:00 Andrew Lunn <andrew@lunn.ch>:
>> >> >> +#ifdef CONFIG_MTD
>> >> >> +     /* NOTE: this should go away as soon as MTD gets nvmem support. */
>> >> >> +     if (!addr) {
>> >> >> +             struct mtd_info *mtd;
>> >> >> +             int rv;
>> >> >> +
>> >> >> +             mtd = get_mtd_device_nm("MAC-Address");
>> >> >
>> >> > In order for this to go away, you need to keep backwards
>> >> > compatibility. When using nvmem, you look for a cell called
>> >> > "mac-address". Here you are looking for "MAC-Address". That is going
>> >> > to make backwards compatibility harder. How do you plan to do it?
>> >> >
>> >> >    Andrew
>> >>
>> >> I'm trying to adjust to already existing users. The only user of
>> >> get_mtd_device_nm() who calls it to read the MAC address registers a
>> >> partition called "MAC-Address". We can't change it since it's visible
>> >> from user space. In the future we'd just have to have a list of
>> >> supported string that we'd use to do the nvmem lookup.
>> >
>> > Why not have the nvmem cell called "MAC-Address"? When you add nvmem
>> > support to MTD, i assume you are going to map each MTD partition to an
>> > nvmem cell?
>>
>> Because all existing users of nvmem use "mac-address" as the name of
>> this cell already. I guess we will need to live with both in this
>> particular function.
>
> So i'm not convinced this last patch is making things better. I would
> prefer if it was dropped for the moment. Wait until MTD via nvmem is
> actually implemented and there is a concrete concept of how a MAC
> address would be looked up without having lots of ugly code.
>
>         Andrew

Unfortunately: this would effectively block me from improving the
support for older davinci boards. Having a (subjectively) ugly but
generalized way of reading the MAC address from MTD is still better
than using the MTD notifier from board files IMO.

Bart