netdev - Re: [PATCH net v2 1/4] auxiliary: Support hexadecimal ids

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Message-ID: <20250723081356.GM402218@unreal>
Date: Wed, 23 Jul 2025 11:13:56 +0300
From: Leon Romanovsky <leon@...nel.org>
To: Sean Anderson <sean.anderson@...ux.dev>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Radhey Shyam Pandey <radhey.shyam.pandey@....com>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	"David S . Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	netdev@...r.kernel.org, Dave Ertman <david.m.ertman@...el.com>,
	Saravana Kannan <saravanak@...gle.com>,
	linux-kernel@...r.kernel.org, Michal Simek <michal.simek@....com>,
	linux-arm-kernel@...ts.infradead.org,
	Ira Weiny <ira.weiny@...el.com>
Subject: Re: [PATCH net v2 1/4] auxiliary: Support hexadecimal ids

On Mon, Jul 21, 2025 at 10:29:32AM -0400, Sean Anderson wrote:
> On 7/20/25 04:17, Leon Romanovsky wrote:
> > On Thu, Jul 17, 2025 at 01:12:08PM -0400, Sean Anderson wrote:
> >> On 7/17/25 12:33, Greg Kroah-Hartman wrote:
> > 
> > <...>
> > 
> >> Anyway, if you really think ids should be random or whatever, why not
> >> just ida_alloc one in axiliary_device_init and ignore whatever's
> >> provided? I'd say around half the auxiliary drivers just use 0 (or some
> >> other constant), which is just as deterministic as using the device
> >> address.
> > 
> > I would say that auxiliary bus is not right fit for such devices. This
> > bus was introduced for more complex devices, like the one who has their
> > own ida_alloc logic.
> 
> I'd say that around 2/3 of the auxiliary drivers that have non-constant
> ids use ida_alloc solely for the auxiliary bus and for no other purpose.
> I don't think that's the kind of complexity you're referring to.
> 
> >> Another third use ida_alloc (or xa_alloc) so all that could be
> >> removed.
> > 
> > These ID numbers need to be per-device.
> 
> Why? They are arbitrary with no semantic meaning, right?

Yes, officially there is no meaning, and this is how we would like to
keep it.

Right now, they are very correlated with with their respective PCI function number.
Is it important? No, however it doesn't mean that we should proactively harm user
experience just because we can do it.

[leonro@c ~]$ l /sys/bus/auxiliary/devices/
,,,
rwxrwxrwx 1 root root 0 Jul 21 15:25 mlx5_core.rdma.0 -> ../../../devices/pci0000:00/0000:00:02.7/0000:0
8:00.0/mlx5_core.rdma.0
lrwxrwxrwx 1 root root 0 Jul 21 15:25 mlx5_core.rdma.1 -> ../../../devices/pci0000:00/0000:00:02.7/0000:0
8:00.1/mlx5_core.rdma
...

Thanks

> 
> --Sean
>