netdev - Re: [PATCH v2 10/35] brcmfmac: firmware: Allow platform to override macaddr

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Message-ID: <ef7e23e3-ebbf-090c-f571-6993dac2d01d@marcan.st>
Date:   Mon, 17 Jan 2022 15:38:59 +0900
From:   Hector Martin <marcan@...can.st>
To:     Arend van Spriel <arend.vanspriel@...adcom.com>,
        Kalle Valo <kvalo@...eaurora.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Len Brown <lenb@...nel.org>,
        Arend van Spriel <aspriel@...il.com>,
        Franky Lin <franky.lin@...adcom.com>,
        Hante Meuleman <hante.meuleman@...adcom.com>,
        Chi-hsien Lin <chi-hsien.lin@...ineon.com>,
        Wright Feng <wright.feng@...ineon.com>,
        Dmitry Osipenko <digetx@...il.com>
Cc:     Sven Peter <sven@...npeter.dev>,
        Alyssa Rosenzweig <alyssa@...enzweig.io>,
        Mark Kettenis <kettenis@...nbsd.org>,
        Rafał Miłecki <zajec5@...il.com>,
        Pieter-Paul Giesberts <pieter-paul.giesberts@...adcom.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Hans de Goede <hdegoede@...hat.com>,
        "John W. Linville" <linville@...driver.com>,
        "brian m. carlson" <sandals@...stytoothpaste.net>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-acpi@...r.kernel.org, brcm80211-dev-list.pdl@...adcom.com,
        SHA-cyfmac-dev-list@...ineon.com
Subject: Re: [PATCH v2 10/35] brcmfmac: firmware: Allow platform to override
 macaddr

On 09/01/2022 05.14, Arend van Spriel wrote:
> On 1/4/2022 8:26 AM, Hector Martin wrote:
>> On Device Tree platforms, it is customary to be able to set the MAC
>> address via the Device Tree, as it is often stored in system firmware.
>> This is particularly relevant for Apple ARM64 platforms, where this
>> information comes from system configuration and passed through by the
>> bootloader into the DT.
>>
>> Implement support for this by fetching the platform MAC address and
>> adding or replacing the macaddr= property in nvram. This becomes the
>> dongle's default MAC address.
>>
>> On platforms with an SROM MAC address, this overrides it. On platforms
>> without one, such as Apple ARM64 devices, this is required for the
>> firmware to boot (it will fail if it does not have a valid MAC at all).
> 
> What overrides what. Can you elaborate a bit?

The behavior seems to be:

- Use the NVRAM MAC address, if any
- Use the SROM MAC address, if any
- Fail to boot

So a platform with a module containing a MAC address may choose to
override it using the DT mechanism with this patch. This is consistent
with the behavior of other drivers implementing platform MAC support.

-- 
Hector Martin (marcan@...can.st)
Public Key: https://mrcn.st/pub