README.md



System / usbmsc USB storage driver

This add-on registers a block device driver, then exports the block the device
using the USB storage class driver. In order to use this add-on, your
board-specific logic must provide the function:

void board_usbmsc_initialize(void);


This function will be called by the system/usbmsc indirectly via the boarctl
BOARDIOC_USBDEV_CONTROL command in order to do the actual registration of the
block device drivers. For examples of the implementation of
board_usbmsc_initialize() see
boards/arm/lpc214x/mcu123-lpc214x/src/up_usbmsc.c or
boards/arm/stm32/stm3210e-eval/src/usbmsc.c.

Configuration options:


CONFIG_NSH_BUILTIN_APPS – This add-on can be built as two NSH built-in
commands if this option is selected: msconn will connect the USB mass
storage device; msdis will disconnect the USB storage device.
CONFIG_LIB_BOARDCTL – Enables the boardctl() interfaces.
CONFIG_BOARDCTL_USBDEVCTRL – Enables the BOARDIOC_USBDEV_CONTROL
boardctl() command.
CONFIG_SYSTEM_USBMSC_NLUNS – Defines the number of logical units (LUNs)
exported by the USB storage driver. Each LUN corresponds to one exported block
driver (or partition of a block driver). May be 1, 2, or 3. Default is
1.
CONFIG_SYSTEM_USBMSC_DEVMINOR1 – The minor device number of the block driver
for the first LUN. For example, N in /dev/mmcsdN. Used for registering the
block driver. Default is zero.
CONFIG_SYSTEM_USBMSC_DEVPATH1 – The full path to the registered block
driver. Default is /dev/mmcsd0
CONFIG_SYSTEM_USBMSC_DEVMINOR2 and CONFIG_SYSTEM_USBMSC_DEVPATH2

Similar parameters that would have to be provided if
CONFIG_SYSTEM_USBMSC_NLUNS is 2 or 3. No defaults.
CONFIG_SYSTEM_USBMSC_DEVMINOR3 and CONFIG_SYSTEM_USBMSC_DEVPATH3

Similar parameters that would have to be provided if
CONFIG_SYSTEM_USBMSC_NLUNS is 3. No defaults.
CONFIG_SYSTEM_USBMSC_DEBUGMM – Enables some debug tests to check for memory
usage and memory leaks.


If CONFIG_USBDEV_TRACE is enabled (or CONFIG_DEBUG_FEATURES and
CONFIG_DEBUG_USB), then the code will also manage the USB trace output. The
amount of trace output can be controlled using:


CONFIG_SYSTEM_USBMSC_TRACEINIT – Show initialization events.

CONFIG_SYSTEM_USBMSC_TRACECLASS – Show class driver events.

CONFIG_SYSTEM_USBMSC_TRACETRANSFERS – Show data transfer events.

CONFIG_SYSTEM_USBMSC_TRACECONTROLLER – Show controller events.

CONFIG_SYSTEM_USBMSC_TRACEINTERRUPTS – Show interrupt-related events.


Error results are always shown in the trace output

Note 1: When built as an NSH add-on command (CONFIG_NSH_BUILTIN_APPS=y),
Caution should be used to assure that the SD drive (or other storage device) is
not in use when the USB storage device is configured. Specifically, the SD
driver should be unmounted like:

nsh> mount -t vfat /dev/mmcsd0 /mnt/sdcard  # Card is mounted in NSH
...
nsh> umount /mnd/sdcard                     # Unmount before connecting USB!!!
nsh> msconn                                 # Connect the USB storage device
...
nsh> msdis                                  # Disconnect USB storate device
nsh> mount -t vfat /dev/mmcsd0 /mnt/sdcard  # Restore the mount


Failure to do this could result in corruption of the SD card format.

Note 2: This add-on used internal USB device driver interfaces. As such, it
relies on internal OS interfaces that are not normally available to a user-space
program. As a result, this add-on cannot be used if a NuttX is built as a
protected, supervisor kernel (CONFIG_BUILD_PROTECTED or
CONFIG_BUILD_KERNEL).