As there is only one bit used in 'flags', and it is only used in case
update_interval is not null, we can move the bit to UpdateIntervalData.

The size of UpdateIntervalData does not increase (on 32 bit).

Reduces RAM usage by 3.6KB (tested on a Pixracer).

 - uORB topics should not be Devices with bus, address, device id

 - keep portions of internal add/remove helpers

This fixes the case where a topic instance is already subscribed, and
advertised later. The subscriber will create the DeviceNode with default
priority, and the advertiser will just use the existing DeviceNode,
without updating to the requested priority.

Also added builtin command wait_for_topic

Signed-off-by: Mark Charlebois <charlebm@gmail.com>

The limits the maximum queue size to 255, which I think is ok for the
forseable future.

sizeof(uORB::DeviceNode) is reduces from 128 to 112 on NuttX, and with
~80 instances, this saves over 1KB of RAM.

this makes it consistent with other functions, like px4_task_spawn_cmd()
and px4_task_kill()

uORB was refactored in order to support the MuORB changes required
for QURT. Those changes wil be added in a subsequent commit.

The files are split out by posix and nuttx so the changes are visible.
When this has been tested, the files can be re-merged and re-tested.

Signed-off-by: Mark Charlebois <charlebm@gmail.com>

Changed "linux" target to "posix". Most of the changes are shared with
QuRT and with OSX. The Linux specific parts are in for i2c which uses
<linux/i2c.h> and <linux/i2c-dev.h>.

There is also a check for __PX4_LINUX in mavlink for a tty ioctl that is
not supported.

Signed-off-by: Mark Charlebois <charlebm@gmail.com>

To avoid confusion when a real device and a virtual device is
being used, changed CDev to VDev for Linux.

Signed-off-by: Mark Charlebois <charlebm@gmail.com>

Signed-off-by: Mark Charlebois <charlebm@gmail.com>

Modified code to use OS independent header file for config settings.

Signed-off-by: Mark Charlebois <charlebm@gmail.com>

this keeps it small enough to fit in a float, which makes it possible
to see the full value in a MAVLink tlog

Conflicts:
	mavlink/include/mavlink/v1.0

this device ID identifies a specific device via the tuple of (bus, bus
type, address, devtype). This allows device specific configuration
data to be stored along with a device ID, so the code can know when
the user has changed device configuration (such as removing an
external compass), and either invalidate the device configuration or
force the user to re-calibrate

this allows drivers to register generic device names for a device
class, with automatic class instance handling

this allows drivers to register generic device names for a device
class, with automatic class instance handling

Add direct-access methods to the base Device class, so that there's a common way of talking to drivers regardless of which of the specialised classes they derive from.

Make the Device destructor public and virtual, so that arbitrary devices can be deleted. Likewise for classes that derive from it.

Make Device::init public so that arbitrary devices can be initialised after being returned by factories.