Re: [PATCH v2 09/27] thunderbolt: Convert switch to a device

[Mika Westerberg]

On Sat, May 27, 2017 at 06:45:24PM +0300, Andy Shevchenko wrote:
> On Fri, May 26, 2017 at 7:09 PM, Mika Westerberg
> <mika.westerberg@xxxxxxxxxxxxxxx> wrote:
> > Thunderbolt domain consists of switches that are connected to each
> > other, forming a bus. This will convert each switch into a real Linux
> > device structure and adds them to the domain. The advantage here is
> > that we get all the goodies from the driver core, like reference
> > counting and sysfs hierarchy for free.
> >
> > Also expose device identification information to the userspace via new
> > sysfs attributes.
> >
> > In order to support internal connection manager (ICM) we separate switch
> > configuration into its own function (tb_switch_configure()) which is
> > only called by the existing native connection manager implementation
> > used on Macs.
> 
> > +       /*
> > +        * The newer controllers include fused UUID as part of link
> > +        * controller specific registers
> > +        */
> > +       cap = tb_switch_find_vsec_cap(sw, TB_VSEC_CAP_LINK_CONTROLLER);
> > +       if (cap > 0) {
> > +               tb_sw_read(sw, uuid, TB_CFG_SWITCH, cap + 3, 4);
> > +       } else {
> > +               /*
> > +                * By default the UUID will be based on UID where upper two
> > +                * dwords are filled with ones.
> > +                */
> > +               uuid[0] = sw->uid & 0xffffffff;
> > +               uuid[1] = (sw->uid >> 32) & 0xffffffff;
> > +               uuid[2] = 0xffffffff;
> > +               uuid[3] = 0xffffffff;
> > +       }
> 
> It might make sense to add some comment as we discussed earlier
> (privately) about (non-)compatibiliness with UUID by spec and why 0xff
> are used.

OK, I'll update the comment here and also reword the attribute
description in sysfs-bus-thunderbolt.