在哪儿linux内核配置usb,linux usb gadget kernel配置

reference:

https://www.linux4sam.org/bin/view/Linux4SAM/USBGadgetConfig

there are TWO kind of gadget configuration

1) USB Gadget functions configurable through configfs(config it in userspace)

2) USB Gadget precomposed configurations(config it in kernel)

1. USB Gadget functions configurable through configfs

A Linux USB "gadget" can be set up through configfs.

If this is the case, the USB functions (which from the host's

perspective are seen as interfaces) and configurations are

specified simply by creating appropriate directories in configfs.

Associating functions with configurations is done by creating

appropriate symbolic links.

For more information see Documentation/usb/gadget_configfs.txt.

USB Gadget ConfigFS is an interface that allows definition of arbitrary functions and configurations to define an application specific USB composite device from userspace.

2. USB Gadget precomposed configurations

A Linux "Gadget Driver" talks to the USB Peripheral Controller

driver through the abstract "gadget" API.  Some other operating

systems call these "client" drivers, of which "class drivers"

are a subset (implementing a USB device class specification).

A gadget driver implements one or more USB functions using

the peripheral hardware.

Gadget drivers are hardware-neutral, or "platform independent",

except that they sometimes must understand quirks or limitations

of the particular controllers they work with.  For example, when

a controller doesn't support alternate configurations or provide

enough of the right types of endpoints, the gadget driver might

not be able work with that controller, or might need to implement

a less common variant of a device class protocol.

The available choices each represent a single precomposed USB

gadget configuration. In the device model, each option contains

both the device instantiation as a child for a USB gadget

controller, and the relevant drivers for each function declared

by the device.

once we insmod gadget driver we can use it!!

This option configures the gadget directly from the kernel config using precomposed configuration. The are multiple options here from simple devices like CDC ACM, Mass storgae, RNDIS, etc. to composite devices like Ethernet + ACM

choose serial gadget