linux-kernel - Re: [PATCH v2 2/2] ARM: dts: Add nvmem node for BCM2711 bootloader public key

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Message-ID: <02a4ebb4-7652-fb1f-ae56-920648470c67@i2se.com>
Date:   Sun, 16 Apr 2023 15:11:02 +0200
From:   Stefan Wahren <stefan.wahren@...e.com>
To:     "Ivan T. Ivanov" <iivanov@...e.de>
Cc:     Nicolas Saenz Julienne <nsaenz@...nel.org>,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        Florian Fainelli <f.fainelli@...il.com>,
        Phil Elwell <phil@...pberrypi.com>,
        linux-rpi-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Tim Gover <tim.gover@...pberrypi.com>
Subject: Re: [PATCH v2 2/2] ARM: dts: Add nvmem node for BCM2711 bootloader
 public key

Hi,

Am 13.04.23 um 21:28 schrieb Tim Gover:
> On Thu, 13 Apr 2023 at 19:44, Stefan Wahren <stefan.wahren@...e.com> wrote:
>>
>> Hi Ivan,
>>
>> Am 13.04.23 um 20:18 schrieb Ivan T. Ivanov:
>>> On 04-13 18:15, Stefan Wahren wrote:
>>>>
>>>> Hi Ivan,
>>>>
>>>> Am 13.04.23 um 10:52 schrieb Ivan T. Ivanov:
>>>>> From: Tim Gover <tim.gover@...pberrypi.com>
>>>>>
>>>>> Make a copy of the bootloader secure-boot public key available to the OS
>>>>> via an nvmem node. The placement information is populated by the
>>>>> Raspberry Pi firmware if a public key is present in the BCM2711
>>>>> bootloader EEPROM.
>>>>
>>>> It would be nice to have a helpful link like:
>>>> https://www.raspberrypi.com/documentation/computers/configuration.html#nvmem-nodes
>>>
>>> Yep, make sense.
>>>
>>>>> +
>>>>> +   /*
>>>>> +    * RPi4 will copy the binary public key blob (if present) from the bootloader
>>>>> +    * into memory for use by the OS.
>>>>> +    */
>>>>> +   blpubkey: nvram@1 {
>>>>> +           compatible = "raspberrypi,bootloader-public-key", "nvmem-rmem";
>>>>
>>>> Yes this looks better, but this introduce a new dtbs_check issue. The new
>>>
>>> Oops, yes, I forgot to make this check.
>>>
>>>> compatible must be documented in
>>>> Documentation/devicetree/bindings/nvmem/rmem.yaml in a separate patch and
>>>> reviewed by the DT guys.
>>>
>>> Or I can drop the new compatible string altogether? It looks like
>>> only alias is strictly required?! Tim Gover is this correct?
>>
>> i cannot speak for the firmware side, but i think we should try to keep
>> it compatible with the vendor DTB here.
>>
> 
> The firmware doesn't look at the compatible string. It locates the
> nodes to update using the 'blconfig' and 'blpubkey' aliases. Userspace
> scripts (including the documentation example) should also use these
> aliases.
> Therefore, I don't think it matters if the compatible strings is
> modified, but I won't pretend to know what the correct DT style is
> here :)

okay, regardless of the compatible string the patch must be send to the 
DT maintainers and the devicetree mailing list otherwise they don't have 
any chance to review.

Thanks

> 
> Tim