nuttx/Documentation/components/drivers/special/usbhost.rst
raiden00pl 07c4bf0048 !arch/stm32: move stm32l1 and finalize the directory split
Move the stm32l1 sources, headers and boards into arch/arm/src/stm32l1,
arch/arm/include/stm32l1 and boards/arm/stm32l1, then finalize the split:
source each split family directly in arch/arm/Kconfig and boards/Kconfig and
remove the now-empty combined arch/arm/src/stm32 and boards/arm/stm32 trees.

BREAKING CHANGE: The legacy STM32 architecture and board paths were split into
stm32f1, stm32l1, stm32f2, stm32f3, stm32f4, and stm32g4 directories.
Out-of-tree boards must move from stm32 to the matching split family.

Signed-off-by: raiden00pl <raiden00@railab.me>
2026-06-24 14:54:44 -03:00

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6.1 KiB
ReStructuredText

=====================
USB Host-Side Drivers
=====================
- **USB host controller driver** abstracts the host controller
device in the target chip. Each USB host controller driver
must implement an instance of ``struct usbhost_driver_s`` and
``struct usbhost_connection_s`` defined in
``include/nuttx/usb/usbhost.h``.
- ``struct usbhost_driver_s`` provides the interface between
the USB host driver and the USB host class driver.
- ``struct usbhost_connection_s`` provides the interface between
the USB host driver and platform-specific connection management
and device enumeration logic.
**Examples**: ``arch/arm/src/lpc17xx_40xx/lpc17_40_usbhost.c``,
``arch/arm/src/common/stm32/stm32_otgfshost_m3m4_v1.c``,
``arch/arm/src/sama5/sam_ohci.c``, and
``arch/arm/src/sama5/sam_ehci.c``.
- **USB host class driver** abstracts USB peripherals connected to
the USB host controller. Each USB host class driver must implement
an instance of ``struct usbhost_class_s`` defined also in
``include/nuttx/usb/usbhost.h``.
**Examples**: ``drivers/usbhost/usbhost_storage.c``
- **USB Host Class Driver Registry**. The NuttX USB host
infrastructure includes a *registry*. During its
initialization, each USB host class driver must call the
interface, ``usbhost_registerclass()`` in order to add its
interface to the registry. Later, when a USB device is
connected, the USB host controller will look up the USB host
class driver that is needed to support the connected device in
this registry.
**Examples**: ``drivers/usbhost/usbhost_registry.c``,
``drivers/usbhost/usbhost_registerclass.c``, and
``drivers/usbhost/usbhost_findclass.c``,
- **Detection and Enumeration of Connected Devices**. Each USB
host device controller supports two methods that are used to
detect and enumeration newly connected devices (and also detect
disconnected devices):
- ``int (*wait)(FAR struct usbhost_connection_s *drvr, FAR const bool *connected);``
Wait for a device to be connected or disconnected.
- ``int (*enumerate)(FAR struct usbhost_connection_s *drvr, int rhpndx);``
Enumerate the device connected to a root hub port. As part
of this enumeration process, the driver will (1) get the
device's configuration descriptor, (2) extract the class ID
info from the configuration descriptor, (3) call
``usbhost_findclass(``) to find the class that supports this
device, (4) call the ``create()`` method on the
``struct usbhost_registry_s interface`` to get a class
instance, and finally (5) call the ``connect()`` method of
the ``struct usbhost_class_s`` interface. After that, the
class is in charge of the sequence of operations.
- **Binding USB Host-Side Drivers**. USB host-side controller
drivers are not normally directly accessed by user code, but
are usually bound to another, higher level USB host class
driver. The class driver exports the standard NuttX device
interface so that the connected USB device can be accessed just
as with other, similar, on-board devices. For example, the USB
host mass storage class driver
(``drivers/usbhost/usbhost_storage.c``) will register a
standard, NuttX block driver interface (like ``/dev/sda``) that
can be used to mount a file system just as with any other other
block driver instance. In general, the binding sequence is:
#. Each USB host class driver includes an initialization entry
point that is called from the application at initialization
time. This driver calls ``usbhost_registerclass()`` during
this initialization in order to makes itself available in
the event the device that it supports is connected.
**Examples**: The function ``usbhost_msc_initialize()`` in
the file ``drivers/usbhost/usbhost_storage.c``
#. Each application must include a *waiter* thread that
(1) calls the USB host controller driver's ``wait()`` to
detect the connection of a device, and then (2) call the USB
host controller driver's ``enumerate`` method to bind the
registered USB host class driver to the USB host controller
driver.
#. As part of its operation during the binding operation, the
USB host class driver will register an instances of a
standard NuttX driver under the ``/dev`` directory. To
repeat the above example, the USB host mass storage class
driver (``drivers/usbhost/usbhost_storage.c``) will register
a standard, NuttX block driver interface (like ``/dev/sda``)
that can be used to mount a file system just as with any
other other block driver instance.
**Examples**: See the call to ``register_blockdriver()`` in
the function ``usbhost_initvolume()`` in the file
``drivers/usbhost/usbhost_storage.c``.
CDC-ECM Host Class Driver
=========================
The CDC-ECM (Ethernet Control Model) host class driver
(``drivers/usbhost/usbhost_cdcecm.c``) supports USB devices that expose
a network interface using the USB Communications Device Class Ethernet
Control Model. Common device types include:
- **USB-to-Ethernet adapters** that implement CDC-ECM, providing wired
Ethernet connectivity over a USB port.
- **Cellular modems and similar devices** that expose a CDC-ECM
interface for IP connectivity, such as LTE modems operating in USB
tethering mode.
When a compatible device is connected and enumerated, the driver
registers a standard NuttX Ethernet network interface — for example
``eth0`` — and integrates with the NuttX networking stack in exactly the
same way as any on-board Ethernet driver. Normal network configuration
can then be applied to the interface using standard NSH commands::
ifup eth0
ifconfig eth0 192.168.1.10 netmask 255.255.255.0
Or with DHCP via the ``netinit`` daemon when
``CONFIG_NETINIT_DHCPC=y`` is selected.
The driver is registered by calling ``usbhost_cdcecm_initialize()``
during board initialization, before the USB host waiter thread begins
enumerating devices.
**Examples**: ``drivers/usbhost/usbhost_cdcecm.c``,
``boards/arm/stm32h5/nucleo-h563zi/configs/nshusbnet/defconfig``.