87 lines
4.5 KiB
Plaintext
87 lines
4.5 KiB
Plaintext
NuttX-5.16
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The 63rd release of NuttX, Version 5.16, was made on January 10,
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2010 and is available for download from the SourceForge website.
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This release includes initial support for USB host in NuttX. The
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USB host infrastructure is new to NuttX. This initial USB host release
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is probably only beta quality; it is expected the some bugs remain
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in the logic and that the functionality requires extension.
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Below is a summary of the NuttX USB host implementation as extracted
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from the NuttX Porting Guide:
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6.3.9 USB Host-Side Drivers
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* include/nuttx/usb/usbhost.h. All structures and APIs needed to
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work with USB host-side drivers are provided in this header
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file.
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* struct usbhost_driver_s. Each USB host controller driver must
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implement an instance of struct usbhost_driver_s. This structure
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is defined in include/nuttx/usb/usbhost.h. Examples:
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arch/arm/src/lpc17xx/lpc17_usbhost.c.
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* struct usbhost_class_s. Each USB host class driver must implement
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an instance of struct usbhost_class_s. This structure is also
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defined in include/nuttx/usb/usbhost.h. Examples:
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drivers/usbhost/usbhost_storage.c
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* USB Host Class Driver Registry. The NuttX USB host infrastructure
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includes a registry. During its initialization, each USB host
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class driver must call the interface, usbhost_registerclass()
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in order add its interface to the registry. Later, when a USB
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device is connected, the USB host controller will look up the
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USB host class driver that is needed to support the connected
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device in this registry. Examples: drivers/usbhost/usbhost_registry.c,
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drivers/usbhost/usbhost_registerclass.c, and
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drivers/usbhost/usbhost_findclass.c,
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* Detection and Enumeration of Connected Devices. Each USB host
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device controller supports two methods that are used to detect
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and enumeration newly connected devices (and also detect
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disconnected devices):
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+ int (*wait)(FAR struct usbhost_driver_s *drvr, bool connected);
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Wait for a device to be connected or disconnected.
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+ int (*enumerate)(FAR struct usbhost_driver_s *drvr);
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Enumerate the connected device. As part of this enumeration
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process, the driver will (1) get the device's configuration
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descriptor, (2) extract the class ID info from the configuration
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descriptor, (3) call usbhost_findclass() to find the class
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that supports this device, (4) call the create() method on
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the struct usbhost_registry_s interface to get a class instance,
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and finally (5) call the connect() method of the struct
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usbhost_class_s interface. After that, the class is in charge
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of the sequence of operations.
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* Binding USB Host-Side Drivers. USB host-side controller drivers
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are not normally directly accessed by user code, but are usually
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bound to another, higher level USB host class driver. The class
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driver exports the standard NuttX device interface so that the
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connected USB device can be accessed just as with other, similar,
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on-board devices. For example, the USB host mass storage class
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driver (drivers/usbhost/usbhost_storage.c) will register a
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standard, NuttX block driver interface (like /dev/sda) that can
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be used to mount a file system just as with any other other
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block driver instance. In general, the binding sequence is:
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1. Each USB host class driver includes an initialization entry
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point that is called from the application at initialization
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time. This driver calls usbhost_registerclass() during this
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initialization in order to makes itself available in the
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event that the device that it supports is connected. Examples:
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The function usbhost_storageinit() in the file
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drivers/usbhost/usbhost_storage.c
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2. Each application must include a waiter thread thread that
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(1) calls the USB host controller driver's wait() to detect
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the connection of a device, and then (2) call the USB host
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controller driver's enumerate method to bind the registered
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USB host class driver to the USB host controller driver.
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Examples: The function nsh_waiter() in the file
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configs/nucleus2g/src/up_nsh.c and the function nsh_waiter()
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in the file configs/olimex-lpc1766stk/src/up_nsh.c.
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3. As part of its operation during the binding operation, the
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USB host class driver will register an instances of a standard
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NuttX driver under the /dev directory. To repeat the above
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example, the USB host mass storage class driver
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(drivers/usbhost/usbhost_storage.c) will register a standard,
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NuttX block driver interface (like /dev/sda) that can be
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used to mount a file system just as with any other other
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block driver instance. Examples: See the call to
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register_blockdriver() in the function usbhost_initvolume()
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in the file drivers/usbhost/usbhost_storage.c.
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