From 93d444d1aade59b5e88f41b71c842a00ab950c64 Mon Sep 17 00:00:00 2001
From: Andrew Tridgell <tridge@samba.org>
Date: Tue, 8 Jul 2014 21:09:12 +1000
Subject: [PATCH] device: added a _device_id to all drivers

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
---
 src/drivers/device/device.cpp | 12 ++++++++++++
 src/drivers/device/device.h   | 25 +++++++++++++++++++++++++
 src/drivers/device/i2c.cpp    |  8 +++++++-
 src/drivers/device/spi.cpp    |  6 ++++++
 src/drivers/drv_device.h      |  7 +++++++
 5 files changed, 57 insertions(+), 1 deletion(-)

diff --git a/src/drivers/device/device.cpp b/src/drivers/device/device.cpp
index 6834551493..f1f777dce0 100644
--- a/src/drivers/device/device.cpp
+++ b/src/drivers/device/device.cpp
@@ -42,6 +42,7 @@
 #include <nuttx/arch.h>
 #include <stdio.h>
 #include <unistd.h>
+#include <drivers/drv_device.h>
 
 namespace device
 {
@@ -93,6 +94,13 @@ Device::Device(const char *name,
 	_irq_attached(false)
 {
 	sem_init(&_lock, 0, 1);
+        
+	/* setup a default device ID. When bus_type is UNKNOWN the
+	   other fields are invalid */
+	_device_id.devid_s.bus_type = DeviceBusType_UNKNOWN;
+	_device_id.devid_s.bus = 0;
+	_device_id.devid_s.address = 0;
+	_device_id.devid_s.devtype = 0;
 }
 
 Device::~Device()
@@ -238,6 +246,10 @@ Device::write(unsigned offset, void *data, unsigned count)
 int
 Device::ioctl(unsigned operation, unsigned &arg)
 {
+	switch (operation) {
+	case DEVIOCGDEVICEID:
+		return (int)_device_id.devid;
+	}
 	return -ENODEV;
 }
 
diff --git a/src/drivers/device/device.h b/src/drivers/device/device.h
index d99f229220..c98386eb07 100644
--- a/src/drivers/device/device.h
+++ b/src/drivers/device/device.h
@@ -124,9 +124,34 @@ public:
 	 */
 	virtual int	ioctl(unsigned operation, unsigned &arg);
 
+	/*
+	  device bus types for DEVID
+	 */
+	enum DeviceBusType {
+		DeviceBusType_UNKNOWN = 0,
+		DeviceBusType_I2C     = 1,
+		DeviceBusType_SPI     = 2
+	};
+
+	/*
+	  broken out 
+	 */
+	struct DeviceStructure {
+		enum DeviceBusType bus_type;
+		uint8_t bus;       // which instance of the bus type
+		uint8_t address;   // address on the bus (eg. I2C address)
+		uint8_t devtype;   // device class specific device type
+	};
+
+	union DeviceId {
+		struct DeviceStructure devid_s;
+		uint32_t devid;
+	};
+
 protected:
 	const char	*_name;			/**< driver name */
 	bool		_debug_enabled;		/**< if true, debug messages are printed */
+	union DeviceId	_device_id;             /**< device identifier information */
 
 	/**
 	 * Constructor
diff --git a/src/drivers/device/i2c.cpp b/src/drivers/device/i2c.cpp
index a416801eb7..286778c014 100644
--- a/src/drivers/device/i2c.cpp
+++ b/src/drivers/device/i2c.cpp
@@ -62,6 +62,12 @@ I2C::I2C(const char *name,
 	_frequency(frequency),
 	_dev(nullptr)
 {
+	// fill in _device_id fields for a I2C device
+	_device_id.devid_s.bus_type = DeviceBusType_I2C;
+	_device_id.devid_s.bus = bus;
+	_device_id.devid_s.address = address;
+	// devtype needs to be filled in by the driver
+	_device_id.devid_s.devtype = 0;     
 }
 
 I2C::~I2C()
@@ -201,4 +207,4 @@ I2C::transfer(i2c_msg_s *msgv, unsigned msgs)
 	return ret;
 }
 
-} // namespace device
\ No newline at end of file
+} // namespace device
diff --git a/src/drivers/device/spi.cpp b/src/drivers/device/spi.cpp
index 1ab1dc6997..200acac05a 100644
--- a/src/drivers/device/spi.cpp
+++ b/src/drivers/device/spi.cpp
@@ -75,6 +75,12 @@ SPI::SPI(const char *name,
 	_dev(nullptr),
 	_bus(bus)
 {
+	// fill in _device_id fields for a SPI device
+	_device_id.devid_s.bus_type = DeviceBusType_SPI;
+	_device_id.devid_s.bus = bus;
+	_device_id.devid_s.address = (uint8_t)device;
+	// devtype needs to be filled in by the driver
+	_device_id.devid_s.devtype = 0; 
 }
 
 SPI::~SPI()
diff --git a/src/drivers/drv_device.h b/src/drivers/drv_device.h
index b310beb746..19d55cef38 100644
--- a/src/drivers/drv_device.h
+++ b/src/drivers/drv_device.h
@@ -59,4 +59,11 @@
 /** check publication block status */
 #define DEVIOCGPUBBLOCK	_DEVICEIOC(1)
 
+/**
+ * Return device ID, to enable matching of configuration parameters
+ * (such as compass offsets) to specific sensors
+ */
+#define DEVIOCGDEVICEID	_DEVICEIOC(2)
+
+
 #endif /* _DRV_DEVICE_H */