On Mon, 2019-08-05 at 12:06 +0200, Linus Walleij wrote:

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

quoted

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.

I look into the spec of fsa9480, it indeed detect many USB accessories.
But this driver is used for simplest cases that only uses micro
receptacle with id-pin/vbus-pin

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

Sorry, you mean provide a common API? could you please describe more
clearer about your suggestion?


Introducing a single driver using usb_role_switch will help to keep
transparent for USB controller driver, no matter it uses type-c or micro

Thanks a lot

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

Yours,
Linus Walleij

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