[PATCH v2 07/16] usb: hub: Power on connected M.2 E-key connectors

[Bartosz Golaszewski]

On Wed, 10 Jun 2026 10:40:41 +0200, Chen-Yu Tsai <wenst at chromium.org> said:
> The new M.2 E-key connector can have a USB connection. For the USB device
> on this connector to work, its power must be enabled and the W_DISABLE2#
> signal deasserted. The connector driver handles this and provides a
> toggle over the power sequencing API.
>
> This feature currently only supports a directly connected (no mux in
> between) M.2 E-key connector. Existing USB connector types are not
> covered. The USB A connector was recently added to the onboard devices
> driver. USB B connectors have historically been managed by the USB
> gadget or dual-role device controller drivers. USB C connectors are
> handled by TCPM drivers.
>
> The power sequencing API does not know whether a power sequence provider
> is not needed or not available yet, so we only request it for connectors
> that we know need it, which at this time is just the E-key connector.
>
> On the USB side, the port firmware node (if present) is tied to the
> usb_port device. This device is used to acquire the power sequencing
> descriptor. This allows the provider to tell the different ports on one
> hub apart.
>
> This feature is not implemented in the onboard USB devices driver. The
> power sequencing API expects the consumer device to make the request,
> but there is no device node to instantiate a platform device to tie
> the driver to. The connector is not a child node of the USB host or
> hub, and the graph connection is from a USB port to the connector.
> And the connector itself already has a driver.
>
> Power sequencing is not directly enabled in the connector driver as
> that would completely decouple the timing of it from the USB subsystem.
> It would not be possible for the USB subsystem to toggle the power
> for a power cycle or to disable the port.
>
> This change depends on another change to make the power sequencing
> framework bool instead of tristate. The USB core and hub driver are
> bool, so if the power sequencing framework is built as a module, the
> kernel will fail to link.
>

That bit needs to go away I suppose?

I see Andy has some suggestions but in general I like this approach much better
than adding the pwrseq_get_index() function. Thanks!

Bartosz