Re: [PATCH v8 00/11] add USB GPIO based connection detection driver

On Wed, Jul 24, 2019 at 10:51 AM Chunfeng Yun [off-list ref] wrote:

Because the USB Connector is introduced and the requirement of
usb-connector.txt binding, the old way using extcon to support
USB Dual-Role switch is now deprecated, meanwhile there is no
available common driver when use Type-B connector, typically
using an input GPIO to detect USB ID pin.

However while this was going on,
drivers/extcon/extcon-fsa9480.c was merged and that detects
not only GPIO on the USB port but multiplexed usecases such
as UART over the USB micro PHY (and no that UART is not
a USB UART, but an actual RX/TX over D-/D+).

That driver also measure a whole slew of funny resistance
values on the ID pin, that is how it does its job.

But for just "hey I'm plugged in" we can surely keep this
ID on GPIO detection in the USB subsystem.

I just get a bit insecure about how we should ideally
handle these "funny-PHY's".

Yours,
Linus Walleij

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