Configuration: Attribute Definition Files

The attributes that can be used on a device are defined in two +configuration files. .

Config.hcf +file

The purpose of this file, config.hcf, is to define the attributes that have meaning on this hardware. It specifies +whether attributes:

are read-only
can be read +and written
are simply stored +by the HAL - the non-derived attributes
require calls +to other components to obtain or set their values - the derived attributes.

The file must be created in the ...\Variant\hal\... directory.

Note that:

all supported +attributes must have an entry in the Config file config.hcf
all non-derived +attributes also need an entry in theValues file values.hda.

The build system uses the Perl script halcfg.pl to convert text information in the Config file into a C++ source +file before the C++ compiler is invoked. The generated binary maps +to the data members defined in the HalInternal class. Note that this class is internal to Symbian.

After initial +implementation, any changes to the files will be picked up by the +supplied makefile, ...\hal\config.mke. The necessary +changes are made to the generated config.cpp file +when the HAL is built.

Any additional functions must be added +to the implementation file by hand, e.g. in a file called imp.cpp. However, this would be unusual because all likely +functions are already implemented in ...\hal\src\userhal.cpp.

The config file consists of a number of lines of text in +the form:

where the pair of square brackets indicates optional items.

<attrib>

This is one of the values of the enumeration HALData::TAttribute in the source file ...\hal\inc\hal_data.h

<prop1>, <prop2>,...

These are optional property +specifications defined by the enumeration HALData::TAttributeProperty in the source file ...\hal\inc\hal_data.h. +Where more than one property is specified, they are separated by commas. +If specified, the initial colon is required. Currently, only the two +properties EValid and ESettable are defined. Note that any substring which is not ambiguous within +the enumerated type is acceptable; matching is not case sensitive.

The property EValid is defined implicitly +for all attributes that appear in the Config file. It indicates that +the attribute is meaningful on this platform. Attributes that do not +appear in the Config file do not have this property, and calls to HAL::Get() or HAL::Set() which refer +to those attributes return KErrNotSupported.

The property ESettable, means that an attribute +is modifiable. Calls to HAL::Set() for attributes +without this property return KErrNotSupported.

<implementation>

Defines whether an attribute is derived. It can be:

0, which means +that the specified attribute is not derived, but is just a constant +stored by the HAL.
the name of +a function used to implement HAL::Get() and HAL::Set() for that specified attribute.

Comments

The order in which attributes are defined +is not important. Comments may be included by starting a line with +//. A comment must be on its own line and cannot be appended +to an attribute specification.

Values.hda +file

The purpose of this file, values.hda, is to specify the initial values of the non-derived attributes, those attributes which are simply stored in, and +retrieved from, the HAL. It must be created in the ...\variant\hal\... directory.

The build system uses the Perl script halcfg.pl to convert text information in the Values file +into a C++ source file before the C++ compiler is invoked.

After initial implementation, any changes to the file will be picked +up by the supplied makefile, ...\hal\config.mke. The necessary changes are made to the generated values.cpp file when the HAL is built.

Any additional functions must +be added to the implementation file by hand, e.g. in a file called imp.cpp. However, this would be unusual because all likely +functions are already implemented in ...\hal\src\userhal.cpp.

The values file consists of a number of lines of text in +the form:

<attrib>

This is one of the values of the enumeration HALData::TAttribute defined in the header file ...\hal\inc\hal_data.h.

<value>

This is the initial value of the attribute. +It may be specified in various ways, but depends on the attribute, +and may be one of the following:

a decimal integer +constant
a hexadecimal +integer constant, by prepending 0x
an enumerated +value for those attributes that have a corresponding enumeration in ...\hal\inc\hal_data.h. Note that any substring which +is not ambiguous within the enumerated type is acceptable; matching +is not case sensitive. For example, intel would be +an acceptable abbreviation for EManufacturer_Intel in the enumeration HALData::TManufacturer.
bit1 ++ bit2 + ... + bitn, for those attributes with corresponding +bitmask enumerations in ...\hal\inc\hal_data.h, and declared with the bitmask pseudo-keyword. bit1, bit2 etc. are values of the enumeration. +Any substring which is not ambiguous within the bitmask type is acceptable +and matching is not case sensitive.

Comments

Attributes EMachineUid and EManufacturer should be allocated UID values +in the normal way. These values should be placed in the values file +and in product specific header files, not in ...\hal\inc\hal_data.h.

Example +of a non-derived attribute

A line similar to the following +in the values.hda file defines the machine Uid +to the HAL, and shows how a value is paired to an attribute.

EMachineUid= 0x1000a682

A line similar to the following in the config.hcf file indicates that the value is not derived but is simply stored +by the HAL.

EMachineUid= 0

Example +(1) of a derived attribute

The following line in the config.hcf file shows how to configure the API for the +display contrast. This states that the display contrast is settable, +and that the function to do this is called ProcessDisplayContrast.

EDisplayContrast : set = ProcessDisplayContrast

Example +(2) of a derived attribute

The following lines in the config.hcf file shows how to configure the API for the +display size.

EDisplayXPixels=ProcessDisplayCurrentModeInfo +EDisplayYPixels=ProcessDisplayCurrentModeInfo

This +is read only information, so the entries do not contain the "set" +keyword. The values are derived via the API function ProcessDisplayCurrentModeInfo, and there is no corresponding entry in values.hda.