linux-kernel - Re: [RFC PATCH 1/2] dt-bindings: net: h4-bluetooth: add new bindings for hci

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Date:   Wed, 9 Nov 2022 16:29:52 +0900
From:   Dominique Martinet <dominique.martinet@...ark-techno.com>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        Rob Herring <robh+dt@...nel.org>
Cc:     Marcel Holtmann <marcel@...tmann.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Luiz Augusto von Dentz <luiz.dentz@...il.com>,
        Johan Hedberg <johan.hedberg@...il.com>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org, linux-bluetooth@...r.kernel.org,
        Paolo Abeni <pabeni@...hat.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        "David S . Miller" <davem@...emloft.net>, mizo@...ark-techno.com
Subject: Re: [RFC PATCH 1/2] dt-bindings: net: h4-bluetooth: add new bindings
 for hci_h4

Dominique Martinet wrote on Wed, Nov 09, 2022 at 08:54:42AM +0900:
> This is a pretty terrible design, as the Bluetooth side cannot actually
> know when the device is ready as the initialization takes place, but
> that means there really aren't any property to give here
> 
> (I haven't reproduced during normal boot, but in particular if I run
> bluetoothd before loading the wifi driver, I need to unbind/bind the
> serial device from the hci_uart_h4 driver to recover bluetooth...
> With that in mind it might actually be best to try to coordinate this
> from userspace with btattach after all, and I'd be happy with that if I
> didn't have to fight our init system so much, but as things stand having
> it autoloaded by the kernel is more convenient for us... Which is
> admitedly a weak reason for you all, feel free to tell me this isn't
> viable)

This actually hasn't taken long to bite us: while the driver does work,
we get error messages early on before the firmware is loaded.
(In hindsight, I probably should have waited a few days before sending
this...)


My current workaround is to return EPROBE_DEFER until we can find a
netdev with a known name in the init namespace, but that isn't really
something I'd consider upstreamable for obvious reasons (interfaces can
be renamed or moved to different namespaces so this is inherently racy
and it's just out of place in BT code)

That makes these two patches on their own rather useless as well, so
unless one of you have an idea that's less ugly I'd guess just dropping
this is the way to go, as much as I dislike the idea of adding more
non-upstream code than we already have :(

Thank you both for your time, the replies have been very helpful and
I'll remember for next time I try to submit something!

And if you have a suggestion, I'll be happy to do some legwork to clean
this mess, so feel free to ask :)


Thanks,
-- 
Dominique