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

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Message-ID: <2025072543-senate-hush-573d@gregkh>
Date: Fri, 25 Jul 2025 07:02:24 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: Sean Anderson <sean.anderson@...ux.dev>
Cc: Leon Romanovsky <leon@...nel.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 Thu, Jul 24, 2025 at 09:55:59AM -0400, Sean Anderson wrote:
> On 7/23/25 04:13, Leon Romanovsky wrote:
> > 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
> 
> Well, I would certainly like to have semantic meaning for ids. But apparently
> that is only allowed if you can sneak it past the review process.

Do I need to dust off my "make all ids random" patch again and actually
merge it just to prevent this from happening?

greg k-h