Using QtOpenCL with multiple devices

[elmigranto]

I have 2 videocards (2 GPUs each) (Radeon HD 6990). I'm trying to use both of them in my calculations.
Querying AMD APP platform returns correct number of avail. OpenCL-devices, so I'm creating context with QList< QCLDevice > containing 4 GPUs.

Then I'm creating QCLProgram using QCLContext::createProgramFromSourceFile().

@ clContext.create(clDevices)
clProgram = clContext.createProgramFromSourceFile("test.cl");
/* setting compilier params... */
clProgram.build(clCompilierOptions)@

Problem is, clProgram only sees 1 gpu (clProgram.devices() returns 1). Documentation says:
@bool QCLProgram::build ( const QList<QCLDevice> & devices, const QString & options = QString() )
/If devices is not empty, the program will only be built for devices in the specified list.
Otherwise the program will be built for all devices on the program's context./@
However, using QList<QCLDevice>() as first param leads to same result.

Any advices? Thanks.