Re: EXT :Re: [RFC PATCH 0/2] USB: DTS: allow suggesting busnumber for platform USB bus via DTS alias

["Boyce, Kevin P [US] (AS)" <Kevin.Boyce@xxxxxxx>]

I think that is shortsighted.

I've used udev rules to change network device names based on their specific slot and instance on the PCI bus.  Purposefully removing things like MAC addresses makes It possible to use a common software image (or disk) on many "like" systems (i.e. the old system imaging approach which is very much alive).



-----Original Message-----
From: systemd-devel <systemd-devel-bounces@xxxxxxxxxxxxxxxxxxxxx> On Behalf Of Rob Herring
Sent: Tuesday, December 11, 2018 5:43 PM
To: David R. Piegdon <lkml@xxxxxxxx>
Cc: Mark Rutland <mark.rutland@xxxxxxx>; devicetree@xxxxxxxxxxxxxxx; Mathias Nyman <mathias.nyman@xxxxxxxxxxxxxxx>; Gustavo A. R. Silva <gustavo@xxxxxxxxxxxxxx>; Martin Blumenstingl <martin.blumenstingl@xxxxxxxxxxxxxx>; Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>; linux-usb@xxxxxxxxxxxxxxx; Kay Sievers <kay@xxxxxxxx>; Johan Hovold <johan@xxxxxxxxxx>; linux-kernel@xxxxxxxxxxxxxxx; Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>; Chunfeng Yun <chunfeng.yun@xxxxxxxxxxxx>; systemd-devel@xxxxxxxxxxxxxxxxxxxxx; Roger Quadros <rogerq@xxxxxx>
Subject: EXT :Re:  [RFC PATCH 0/2] USB: DTS: allow suggesting busnumber for platform USB bus via DTS alias

On Tue, Nov 27, 2018 at 04:57:05PM +0000, David R. Piegdon wrote:
> Hi,
> 
> on our embedded systems we rely on systemd's persistent netdev names.
> Those currently do not work for USB netdevs that are connected to a 
> platform USB bus.
> 
> In https://github.com/systemd/systemd/pull/7273 a systemd patch was 
> suggested that would allow exactly this, but it was (rightfully) said 
> that numbering of theses busses is not guaranteed. Internally we used 
> the patch for a while now, but exactly that has happened with one of 
> our platforms across different kernel revisions.
> 
> The following kernel patches allow suggesting a USB busnumber for each 
> USB platform bus via a DTS alias, as can be done similarly for many 
> other devices.
> In combination with above systemd patch, these changes allow use of 
> persistent netdev names also on platform USB busses.

I don't think this is doing what was suggested in the link above. Though I'm not familiar with what ACPI provides. Userspace would still be relying on the Linux enumeration numbering. How would userspace tell if that numbering is persistent or not other than looking at the DT itself (which isn't a good solution either)?

I don't understand though why userspace needs anything more that the mac address of a net device to provide a persistent name.

Rob
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