2 * Copyright (c) 2008 Nokia Corporation and/or its subsidiary(-ies).
4 * This component and the accompanying materials are made available
5 * under the terms of "Eclipse Public License v1.0"
6 * which accompanies this distribution, and is available
7 * at the URL "http://www.eclipse.org/legal/epl-v10.html".
9 * Initial Contributors:
10 * Nokia Corporation - initial contribution.
14 * Description: Sensor channel class definition
19 #ifndef SENSRVCHANNEL_H
20 #define SENSRVCHANNEL_H
23 #include <sensrvtypes.h>
24 #include <sensrvchannelconditionset.h>
25 #include <sensrvchannelinfo.h>
28 class MSensrvPropertyListener;
29 class MSensrvDataListener;
30 class MSensrvChannelConditionListener;
31 class CSensrvChannelCondition;
32 class CSensrvChannelListener;
36 * The CSensrvChannel class provides an API that allows clients to open, control, configure,
37 * receive data and receive notifications from a sensor channel.
39 * When instantiating CSensrvChannel an instance of TSensrvChannelInfo returned by
40 * CSensrvChannelFinder::FindChannelsL() must be used. This ensures that internal data used
41 * in identifying the chosen channel is passed back to Sensor Services in its entirety
42 * therefore ensuring correct operation. Not using the instance returned by
43 * CSensrvChannelFinder::FindChannelsL() will result in undefined behaviour.
45 * On instantiation of this class a session connection to the Sensor Server is made. The Sensor
46 * server is a transient server and is started, if not already running, when a session connection
47 * is made. The sensor server is shutdown when a device-configured timeout period expires after
48 * the last session connection has been dropped. The Sensor Server will not shutdown if there is
49 * a session connection to it.
51 * The instance of TSensrvChannelInfo returned by CSensrvChannelFinder::FindChannelsL()
52 * contains a channel Id which is only valid for the lifetime of the sensor server. If a client
53 * requires that this id remains unchanged then the client must ensure that an instance of either
54 * CSensrvChannelFinder or CSensrvChannel remains instantiated. This keeps a session connection with
55 * the server open which prevents the sensor server from shutting down.
57 * After creating an instance of this class a client would typically:
58 * 1. Check the configuration of the channel using GetPropertyL() or GetAllPropertuies().
59 * 2. Change the configuration where necessary using SetPropertiesL()
60 * 3. If SetPropertiesL() failed, because of higher priority clients of this same channel or higher
61 * priority clients of impacted channels on the same sensor, listen for notifications indicating
62 * when it is able to set properties using SetPropertyListenerl().
63 * 4. Listen for property changes using SetPropertyListenerl(). This notifies the client of property
64 * changes made by other clients of this same channel.
65 * 5. Listen for data and retrieve data on the channel using StartDataListeningL() and GetData().
66 * 6. Set trigger conditions for a 1 off notification when the condition is met using AddConditionL()
67 * and SetConditionListeningL().
69 * Its possible that there may be more than 1 client using the same sensor channel on the device. Each
70 * of these clients will have created their own instance of CSensrvChannel and can attempt to configure
71 * the sensor using the SetPropertyL() operation. To manage any contention between clients wishing to
72 * change the configuration of the sensor a concept of Client Priorities is employed. This means that a
73 * device creator assigns a pre-determined priority to a client. If a client has not been assigned a
74 * priority then it is assumed it has the lowest priority.
76 * When the SetPropertyL() operation is called the sensor server checks to see if the client has the
77 * highest Client Priority of all clients using that channel or using an impacted channel on the same
78 * sensor. If it has the property is set and all other clients of the channel are notified of the property
79 * change. If it has not the SetPropertyL() operation fails with KErrAccessDenied. If clients have
80 * the same priority then property setting is done on a first come first served basis.
82 * If a client is unable to set a property because of higher priority clients then the client should
83 * implement the MSensrvPropertyListener::SetPropertySuccessIndicationChanged() callback so that they can
84 * be notified when they are able to set properties.
86 * All client applications should be designed in such a way so that they are able to handle the situation
87 * where they are unable to configure a channel using the SetPropertyL() operation.
90 * Should application features be disabled or should the application shutdown in such conditions?
91 * Should features be disabled under certain channel configurations?
93 * This object is closed when deleted either by a call to operator delete or by the cleanup stack. No special
94 * cleanup code is necessary to close the object before deletion.
96 * @see CSensrvChannelFinder
97 * @lib sensrvclient.lib
101 NONSHARABLE_CLASS( CSensrvChannel ): public CBase
105 * Two-phased constructor.
107 * The Sensor Server uses aChannelInfo to identify the channel in the server that the returned object
111 * @param aChannelInfo The information that determines which channel object is created. This must
112 * be an object returned by CSensrvChannelFinder::FindChannelsL().
113 * @return Pointer to created CSensorChannel object
114 * @leave KErrNoMemory
115 * @leave One of the system-wide error codes
117 IMPORT_C static CSensrvChannel* NewL
118 ( const TSensrvChannelInfo& aChannelInfo );
121 * Two-phased constructor.
123 * The Sensor Server uses aChannelInfo to identify the channel in the server that the returned object
127 * @param aChannelInfo The information that determines which channel object is created. This must
128 * be an object returned by CSensrvChannelFinder::FindChannelsL().
129 * @return Pointer to created CSensorChannel object that is placed on the cleanup stack.
130 * @leave KErrNoMemory
131 * @leave One of the system-wide error codes
133 IMPORT_C static CSensrvChannel* NewLC
134 ( const TSensrvChannelInfo& aChannelInfo );
138 * Initializes and opens the channel. After the channel is opened, the client can set and get channel
139 * properties, add channel conditions and listen for sensor data.
142 * @leave KErrAlreadyExists if channel is already open
143 * @leave One of the system-wide error codes
145 virtual void OpenChannelL() = 0;
148 * Closes the channel.
150 * This object is closed when deleted either by a call to operator delete or by the cleanup stack. No special
151 * cleanup code is necessary to close the object before deletion.
154 * @return KErrNone if channel closing is successful, or one of the system-wide error codes
156 virtual TInt CloseChannel() = 0;
159 * Retrieves a channel information object related to this channel.
162 * @return Reference to the channel information object
164 virtual const TSensrvChannelInfo& GetChannelInfo() const = 0;
167 * Starts channel data listening on the channel.
169 * To use this operation clients must provide an object that inherits from MSensrvDataListener.
171 * When new data is available to be read, the client is notified by the
172 * MSensrvDataListener::DataReceived() callback. On receiving this notificaton the client should
173 * retrieve the data using the GetData() operation.
175 * Note that if a client is listening for both data and conditions on the channel then the lower
176 * desired count and buffering period provided in either start listening operation arguments will be
177 * used for both listeners. When either listener is stopped neither the desired count nor the
178 * buffering period shall be changed.
180 * For the best performance, always use the highest desired count and maximum count as the use case
181 * allows. This will reduce the overhead caused by a high volume of IPC context switches. However,
182 * be aware that higher counts need to reserve more memory.
185 * @param aDataListener Data listener for the channel. Must be valid until data listening is stopped.
186 * @param aDesiredCount Desired receiving buffer size defined as a count of the channel data objects.
187 * The maximum value is determined by sensor server internal channel buffer size, and minimum
188 * value is one. Any value outside these limits is interpreted as maximum possible value.
189 * The actual count of channel data objects received may be smaller than aDesiredCount, if a
190 * non-zero buffering period has been specified.
191 * The actual count of channel data objects received may larger, if aMaximumCount is bigger
192 * than aDesiredCount.
193 * If the sensor supplies data sporadically, and the clients requires every data object then
194 * aDesiredCount should be set to one to ensure that no data objects are missed.
195 * @param aMaximumCount Maximum receiving buffer size defined as a count of the channel data object.
196 * The Maximum value is determined by sensor server internal channel buffer size, and minimum
197 * value is aDesiredCount. Any value outside these limits is interpreted as maximum possible
199 * It is recommended that whenever aDesiredCount needs to be low and sensor has relatively high
200 * data rate, aMaximumCount is set to significantly higher than aDesiredCount to reduce IPC
201 * context switches and data loss.
202 * @param aBufferingPeriod Specifies the maximum time in milliseconds that sensor server waits before
203 * notifying the client that new data is available. It is possible that no new data is will be
204 * available when the client is notified.
205 * Zero timeout means that only desired and maximum counts are used in getting data.
206 * Using a buffering period results in lot of unnecessary IPC context switches if a sensor
207 * channel supplies data sporadically. It is therefore recommended that a buffering period is
208 * used only when it is absolutely vital to have data at specific intervals and using a low
209 * desired count is otherwise too expensive performance-wise.
210 * @leave KErrArgument if aDataListener is NULL, or if a negative argument is supplied
211 * @leave KErrNotFound if the channel is not open
212 * @leave KErrAlreadyExists if data listening has already started on the channel
213 * @leave One of the system-wide error codes
215 virtual void StartDataListeningL( MSensrvDataListener* aDataListener,
216 const TInt aDesiredCount,
217 const TInt aMaximumCount,
218 const TInt aBufferingPeriod ) = 0;
221 * Stop channel data listening.
224 * @return KErrNone if stopping successful or one of the system-wide error codes
226 virtual TInt StopDataListening() = 0;
229 * Get data items when the client is notified by the MSensrvDataListener::DataReceived() callback
230 * that new data is ready to be retrieved. The callback also indicates the number of data items
231 * contained in aData.
235 * How to retrieve data using TPckg
238 * void DataReceived(CSensrvChannel& aChannel, TInt aCount, TInt aDataLost )
240 * if(aChannel.GetChannelInfo().iChannelType == KSensrvChannelTypeIdAccelerometerXYZAxisData)
242 * TSensrvAccelerometerAxisData XYZData;
243 * TPckg<TSensrvAccelerometerAxisData> XYZPackage( XYZData );
244 * aChannel.GetData( XYZPackage );
250 * @param aData Reference to descriptor that contains the data. Typically this is a package buffer
251 * defined for data type of this channel. See channel specific data headers for details of
252 * the package types and data supported by a channel.
253 * @return KErrNotFound if data buffer is empty, KErrOverflow if aData is wrong size for data
254 * item, or one of the system-wide error codes
256 virtual TInt GetData( TDes8& aData ) = 0;
259 * Sets a property value for this channel. To manage any contention between multiple clients wishing
260 * to change the configuration of the sensor a concept of Client Priorities is employed. See class
261 * description for further information.
263 * The sensor plugin may police setting of properties by verifying that the client making the request
264 * has the necessary capabilities. If the client does not then it will return with KErrAccessDenied.
266 * @param aProperty Identifies the property that is to be set and its new value. Only the Property Id,
267 * Item Index and Property Value should be filled in. All other fields in TSensrvProperty are
269 * @return KErrNotFound if channel is not open or if the property does not exist, KErrAccessDenied
270 * if there are other clients for this channel or impacted channel on the same sensor with a
271 * higher Client Priority, KErrAccessDenied if the client does not have the required
272 * capabilities or one of the system-wide error codes
274 virtual TInt SetProperty( const TSensrvProperty& aProperty ) = 0;
277 * Gets a channel property value for this channel.
280 * @param aPropertyId Id of the property that is to be retrieved
281 * @param aItemIndex The Item Index of the property to be retrieved. This is mapped to a specific item
282 * in channel data structure. See channel specific data headers.
283 * @param aProperty Reference for a property object where property data is to be copied
284 * @leave KErrNotFound if channel is not open
285 * @leave KErrNotFound if property does not exist
286 * @leave KErrArgument if a negative argument is supplied
287 * @leave One of the system-wide error codes
289 virtual void GetPropertyL( const TSensrvPropertyId aPropertyId,
290 const TInt aItemIndex,
291 TSensrvProperty& aProperty ) = 0;
294 * Get a channel property value for this channel
297 * @param aPropertyId Id of the property that is to be retrieved
298 * @param aItemIndex Item Index of the property to be retrieved. This is mapped to a specific item
299 * in channel data structure. See channel specific data headers.
300 * @param aArrayIndex Array index of the property to be retrieved when the property is part of a
302 * @param aProperty Reference for a property object where property data is to be copied
303 * @leave KErrNotFound if channel is not open
304 * @leave KErrNotFound if property does not exist
305 * @leave KErrArgument if a negative argument is supplied
306 * @leave One of the system-wide error codes
308 virtual void GetPropertyL( const TSensrvPropertyId aPropertyId,
309 const TInt aItemIndex,
310 const TInt aArrayIndex,
311 TSensrvProperty& aProperty ) = 0;
314 * Get all properties for this channel
317 * @param aChannelPropertyList Reference for a property list where all property data is to be
318 * copied. Any existing data in the list will be lost.
319 * @leave KErrNotFound if channel is not open
320 * @leave One of the system-wide error codes
322 virtual void GetAllPropertiesL
323 ( RSensrvPropertyList& aChannelPropertyList ) = 0;
326 * Get all channel properties having the supplied Property Id. This is used when the property
327 * is an array property.
330 * @param aPropertyId Id of the property to be retrieved
331 * @param aChannelPropertyList Reference for a property list where all property data is to be
332 * copied. Any existing data in the list will be lost.
333 * @leave KErrNotFound if channel is not open
334 * @leave KErrNotFound if property does not exist
335 * @leave One of the system-wide error codes
337 virtual void GetAllPropertiesL
338 ( const TSensrvPropertyId aPropertyId,
339 RSensrvPropertyList& aChannelPropertyList ) = 0;
342 * Start property listening on this channel.
344 * To use this operation clients must provide an object that inherits from MSensrvPropertyListener.
346 * The client can use the property listener to get notifications when properties are changed and
347 * to get a notification when the client is able/unable to set properties because of higher priority
348 * clients have opened/closed the same sensor channel.
350 * If the client itself changes a property value, no notification is received for that property by
351 * the client. If another client changes a property on this channel or another channel that impacts
352 * this channel a notification will be received by the client.
354 * Some sensors support a number of channels with each channel having some common properties.
355 * Therefore changing a common property may result in notifications on a number of other channels
356 * supported by the sensor.
359 * @param aChannelPropertyListener Pointer to channel property listener callback instance. The
360 * channel property listener must be valid until the CSensrvChannel object is destroyed or
361 * listening has been stopped. Listening can be stopped using a NULL parameter.
362 * @leave KErrAlreadyExists if channel property listener has already been set
363 * @leave KErrNotFound if channel is not open
364 * @leave One of the system-wide error codes
366 virtual void SetPropertyListenerL
367 ( MSensrvPropertyListener* aChannelPropertyListener ) = 0;
370 * Add a channel ConditionSet to the channel.
372 * Channel ConditionSet's are used for channel condition listening and at least 1 ConditionSet must
373 * be added before listening can begin.
375 * When the conditions defined by the ConditionSet is met the client will be notified by the
376 * MSensrvChannelConditionListener::ConditionMet() callback and listening for this ConditionSet will
377 * cease. If a client wishes to listen for this ConditionSet again it must be added again.
379 * The client continues to own the ConditionSet object after a call to this function and must ensure
380 * that it is destroyed when no longer required.
382 * The client must ensure that the ConditionSet object is valid until it is no longer needed by the
383 * Sensor Server. This is either after the condition set has been removed by the client using
384 * RemoveConditionL() or the client has been notified that the condition has been met.
387 * @param aChannelConditionSet The channel condition set to be added.
388 * @leave KErrNotFound if channel is not open
389 * @leave KErrNotSupported if a channel does not support conditions.
390 * @leave One of the system-wide error codes
391 * @see CSensrvChannel::StartConditionListeningL()
393 virtual void AddConditionL( CSensrvChannelConditionSet& aChannelConditionSet ) = 0;
396 * Remove a channel ConditionSet from the channel.
398 * The same reference used to to add the Condition Set in AddConditionL(), must also be used to
401 * The removed channel ConditionSet is no longer used for channel condition listening.
403 * The client continues to own the ConditionSet object after a call to this function and must ensure
404 * that it is destroyed when no longer required.
407 * @param aChannelConditionSet The channel condition set to be removed.
408 * @leave KErrNotFound if channel is not open
409 * @leave One of the system-wide error codes
411 virtual void RemoveConditionL
412 ( CSensrvChannelConditionSet& aChannelConditionSet ) = 0;
415 * Start channel condition listening.
417 * To use this operation clients must provide an object that inherits from MSensrvChannelConditionListener.
419 * If the conditions of an added ConditionSet is met the MSensrvChannelConditionListener::ConditionMet()
420 * callback function will be called and listening for this ConditionSet will cease. If a client wishes
421 * to listen for the same ConditionSet again it must be added again.
423 * Note that if a client is listening for both data and conditions on the channel then the lower
424 * desired count and buffering period provided in either start listening operation arguments will be
425 * used for both listeners. When either listener is stopped neither the desired count nor the
426 * buffering period shall be changed.
429 * @param aChannelConditionListener Condition listener for the channel. Must be valid until data
430 * listening is stopped.
431 * @param aObjectCount Listening buffer size defined as a count of the channel data objects. When the
432 * desired object count is reached each ConditionSet is evaluated in turn. The maximum value is
433 * determined by sensor server internal channel buffer size, and minimum value is one. Any value
434 * outside these limits is interpreted as maximum possible value.
435 * @param aBufferingPeriod Specifies the maximum time in milliseconds that sensor server waits before
436 * evaluating new data.
437 * Zero timeout means that the sensor server only evaluates new data when the object count has been
439 * @leave KErrArgument if aChannelConditionListener is NULL, or if a negative argument is supplied
440 * @leave KErrNotFound if the channel is not open
441 * @leave KErrAlreadyExists if condition listening has already started on the channel
442 * @leave One of the system-wide error codes
444 virtual void StartConditionListeningL
445 ( MSensrvChannelConditionListener* aChannelConditionListener,
446 const TInt aObjectCount,
447 const TInt aBufferingPeriod ) = 0;
450 * Stop channel condition listening.
452 * All remaining unmet ConditionSet's are removed and channel condition listening is stopped.
454 * If the same ConditionSet's need to be used when condition listening has been restarted then they must be
458 * @return KErrNone if condition listening is successfully stopped or one of the system-wide error codes
460 virtual TInt StopConditionListening() = 0;
464 * Default constructor.
470 #endif //SENSRVCHANNEL_H