linux-kernel - Re: [PATCH net 1/4] auxiliary: Allow empty id

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Message-ID: <91a9e80a-1a45-470b-90cf-12faae67debd@linux.dev>
Date: Fri, 20 Jun 2025 12:09:29 -0400
From: Sean Anderson <sean.anderson@...ux.dev>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: 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, Michal Simek <michal.simek@....com>,
 Saravana Kannan <saravanak@...gle.com>, Leon Romanovsky <leon@...nel.org>,
 Dave Ertman <david.m.ertman@...el.com>, linux-kernel@...r.kernel.org,
 Ira Weiny <ira.weiny@...el.com>, linux-arm-kernel@...ts.infradead.org,
 Danilo Krummrich <dakr@...nel.org>, "Rafael J. Wysocki" <rafael@...nel.org>
Subject: Re: [PATCH net 1/4] auxiliary: Allow empty id

On 6/20/25 12:02, Greg Kroah-Hartman wrote:
> On Fri, Jun 20, 2025 at 11:37:40AM -0400, Sean Anderson wrote:
>> On 6/20/25 01:13, Greg Kroah-Hartman wrote:
>> > On Thu, Jun 19, 2025 at 04:05:34PM -0400, Sean Anderson wrote:
>> >> Support creating auxiliary devices with the id included as part of the
>> >> name. This allows for non-decimal ids, which may be more appropriate for
>> >> auxiliary devices created as children of memory-mapped devices. For
>> >> example, a name like "xilinx_emac.mac.802c0000" could be achieved by
>> >> setting .name to "mac.802c0000" and .id to AUXILIARY_DEVID_NONE.
>> > 
>> > I don't see the justification for this, sorry.  An id is just an id, it
>> > doesn't matter what is is and nothing should be relying on it to be the
>> > same across reboots or anywhere else.  The only requirement is that it
>> > be unique at this point in time in the system.
>> 
>> It identifies the device in log messages. Without this you have to read
>> sysfs to determine what device is (for example) producing an error.
> 
> That's fine, read sysfs :)

I should not have to read sysfs to decode boot output. If there is an
error during boot I should be able to determine the offending device.
This very important when the boot process fails before init is started,
and very convenient otherwise. 

>> This
>> may be inconvenient to do if the error prevents the system from booting.
>> This series converts a platform device with a legible ID like
>> "802c0000.ethernet" to an auxiliary device, and I believe descriptive
>> device names produce a better developer experience.
> 
> You can still have 802c0000.ethernet be the prefix of the name, that's
> fine.

This is not possible due to how the auxiliary bus works. If device's
name is in the form "foo.id", then the driver must have an
auxiliary_device_id in its id_table with .name = "foo". So the address
*must* come after the last period in the name.

--Sean

>> This is also shorter and simpler than auto-generated IDs.
> 
> Please stick with auto-generated ids, they will work properly here.
> 
> thanks,
> 
> greg k-h