linux-kernel - Re: exporting a device type

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Message-ID: <Z_mIrjA5k2CABoG_@pollux.localdomain>
Date: Fri, 11 Apr 2025 23:25:02 +0200
From: Danilo Krummrich <dakr@...nel.org>
To: Andy Shevchenko <andy.shevchenko@...il.com>
Cc: Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: exporting a device type

On Fri, Apr 11, 2025 at 10:39:38PM +0300, Andy Shevchenko wrote:
> I have an issue with this change
> 
> https://web.git.kernel.org/pub/scm/linux/kernel/git/dakr/linux.git/commit/?h=for-driver-core&id=e86cc69186051d7312711565803de586efd9b2cf
> 
> (I think you haven't yet sent it for review, so this is just
> preliminary look at)
> 
> The idea of exporting bus type will open a non-reversible box of
> changes when people will start abusing it. Instead just provide an API
> dev_is_auxiliary() as it's done in other subsystems (yes, I know that
> some of them are still exporting the type, but it's most likely due to
> historical reasons of not thinking through it at that time).

Yeah, most busses export it and provide a dev_is_*() macro, which we can't use
in Rust. That's why for PCI and platform I started using the bus type directly,
see e.g. [1].

However, I already considered changing it up by just creating Rust helper
functions for the dev_is_*() macros and provide a dev_is_auxiliary() API
instead. This also simplifies things a bit and gets me rid of the
Device::bus_type_raw() helper.

[1] https://web.git.kernel.org/pub/scm/linux/kernel/git/dakr/linux.git/commit/?h=for-driver-core&id=d72c42c1da4149fec28e3b180654bf5fd88c2094