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SubjectRe: [PATCH v2 09/27] thunderbolt: Convert switch to a device
On Fri, May 26, 2017 at 7:09 PM, Mika Westerberg
<mika.westerberg@linux.intel.com> 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.

--
With Best Regards,
Andy Shevchenko

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