Why is this a kernel-level driver, rather than a userspace application
that uses libusb to send the single vendor-specific command required?
Since this command would be applicable to many CarPlay devices, with
many different VID/PIDs, it would seem to make more sense as a
userspace app that took a reference to a USB device or VID/PID.


On Tue, Mar 13, 2018 at 11:02 PM, Chunfeng Yun
<chunfeng....@mediatek.com> wrote:
> From bf48dcd9cb254576cfea373c9a5d2ab996408895 Mon Sep 17 00:00:00 2001
> From: Chunfeng Yun <chunfeng....@mediatek.com>
> Date: Tue, 13 Mar 2018 11:47:38 +0800
> Subject: [PATCH] Add Apple Carplay driver
> Some Apple devices which support Carplay can enter USB Host Mode from USB
> Device Mode after receiving a specific USB Vendor Request. There is a
> requirement apply to accesssories that support the USB dual role switch
> feature, and must have a USB-A receptacle that is capable of functioning
> in both USB Host and USB Device roles.
> It means that the driver should supports manual Dual-Role switch, due to
> no IDDIG pin is avaliable.
> There is no suitable place to add this spicific USB Vendor Request, so
> here I extract a single driver which allow user force to send it by a debug
> interface when need it, and keep it independent on USB Dual-Role Controller
> Drivers.
> But to implement carplay feature, there are some requirments for USB Dual-Role
> Driver:
> 1. supports manual dual-role switch, such as, by a debug interface;
> 2. keep vbus alive even when switch host into device mode;
> More information please refer to "Chapter 46. USB Role Switch" in
> MFI Accessroy Interface Specification.pdf
> Chunfeng Yun (1):
>   usb: misc: supports Apple Carplay driver
>  drivers/usb/misc/Kconfig   |    9 +++
>  drivers/usb/misc/Makefile  |    1 +
>  drivers/usb/misc/carplay.c |  193 
> ++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 203 insertions(+)
>  create mode 100644 drivers/usb/misc/carplay.c
> --
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Matthew Dharm
Former Maintainer, USB Mass Storage driver for Linux

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