10. Config file ``Option'' entries

Option entries are permitted in most sections and subsections of the config file. There are two forms of option entries:

Option "option-name"

A boolean option.

Option "option-name" "option-value"

An option with an arbitrary value.

The option entries are handled by the parser, and a list of the parsed options is included with each of the appropriate data structures that the drivers have access to. The data structures used to hold the option information are opaque to the driver, and a driver must not access the option data directly. Instead, the common layer provides a set of functions that may be used to access, check and manipulate the option data.

First, the low level option handling functions. In most cases drivers would not need to use these directly.

pointer xf86FindOption(pointer options, const char *name)

Takes a list of options and an option name, and returns a handle for the first option entry in the list matching the name. Returns NULL if no match is found.

char *xf86FindOptionValue(pointer options, const char *name)

Takes a list of options and an option name, and returns the value associated with the first option entry in the list matching the name. If the matching option has no value, an empty string ("") is returned. Returns NULL if no match is found.

void xf86MarkOptionUsed(pointer option)

Takes a handle for an option, and marks that option as used.

void xf86MarkOptionUsedByName(pointer options, const char *name)

Takes a list of options and an option name and marks the first option entry in the list matching the name as used.

Next, the higher level functions that most drivers would use.

void xf86CollectOptions(ScrnInfoPtr pScrn, pointer extraOpts)

Collect the options from each of the config file sections used by the screen (pScrn) and return the merged list as pScrn->options. This function requires that pScrn->confScreen, pScrn->display, pScrn->monitor, pScrn->numEntities, and pScrn->entityList are initialised. extraOpts may optionally be set to an additional list of options to be combined with the others. The order of precedence for options is extraOpts, display, confScreen, monitor, device.

void xf86ProcessOptions(int scrnIndex, pointer options,
          OptionInfoPtr optinfo)

Processes a list of options according to the information in the array of OptionInfoRecs (optinfo). The resulting information is stored in the value fields of the appropriate optinfo entries. The found fields are set to TRUE when an option with a value of the correct type if found, and FALSE otherwise. The type field is used to determine the expected value type for each option. Each option in the list of options for which there is a name match (but not necessarily a value type match) is marked as used. Warning messages are printed when option values don't match the types specified in the optinfo data.

NOTE: If this function is called before a driver's screen number is known (e.g., from the ChipProbe() function) a scrnIndex value of -1 should be used.

The OptionInfoRec is defined as follows:

        typedef struct {
            double freq;
            int units;
        } OptFrequency;

        typedef union {
            unsigned long       num;
            char *              str;
            double              realnum;
            Bool                bool;
            OptFrequency        freq;
        } ValueUnion;

        typedef enum {
            OPTV_NONE = 0,
            OPTV_INTEGER,
            OPTV_STRING,     /* a non-empty string */
            OPTV_ANYSTR,     /* Any string, including an empty one */
            OPTV_REAL,
            OPTV_BOOLEAN,
            OPTV_FREQ
        } OptionValueType;

        typedef enum {
            OPTUNITS_HZ = 1,
            OPTUNITS_KHZ,
            OPTUNITS_MHZ
        } OptFreqUnits;

        typedef struct {
            int                 token;
            const char*         name;
            OptionValueType     type;
            ValueUnion          value;
            Bool                found;
        } OptionInfoRec, *OptionInfoPtr;
        

OPTV_FREQ can be used for options values that are frequencies. These values are a floating point number with an optional unit name appended. The unit name can be one of "Hz", "kHz", "k", "MHz", "M". The multiplier associated with the unit is stored in freq.units, and the scaled frequency is stored in freq.freq. When no unit is specified, freq.units is set to 0, and freq.freq is unscaled.

Typical usage is to setup a static array of OptionInfoRecs with the token, name, and type fields initialised. The value and found fields get set by xf86ProcessOptions(). For cases where the value parsing is more complex, the driver should specify OPTV_STRING, and parse the string itself. An example of using this option handling is included in the Sample Driver section.

void xf86ShowUnusedOptions(int scrnIndex, pointer options)

Prints out warning messages for each option in the list of options that isn't marked as used. This is intended to show options that the driver hasn't recognised. It would normally be called near the end of the ChipScreenInit() function, but only when serverGeneration == 1.

OptionInfoPtr xf86TokenToOptinfo(OptionInfoPtr table, int token)

Returns a pointer to the OptionInfoRec in table with a token field matching token. Returns NULL if no match is found.

Bool xf86IsOptionSet(OptionInfoPtr table, int token)

Returns the found field of the OptionInfoRec in table with a token field matching token. This can be used for options of all types. Note that for options of type OPTV_BOOLEAN, it isn't sufficient to check this to determine the value of the option. Returns FALSE if no match is found.

char *xf86GetOptValString(OptionInfoPtr table, int token)

Returns the value.str field of the OptionInfoRec in table with a token field matching token. Returns NULL if no match is found.

Bool xf86GetOptValInteger(OptionInfoPtr table, int token,
          int *value)

Returns via *value the value.num field of the OptionInfoRec in table with a token field matching token. *value is only changed when a match is found so it can be safely initialised with a default prior to calling this function. The function return value is as for xf86IsOptionSet().

Bool xf86GetOptValULong(OptionInfoPtr table, int token,
          unsigned long *value)

Like xf86GetOptValInteger(), except the value is treated as an unsigned long.

Bool xf86GetOptValReal(OptionInfoPtr table, int token,
          double *value)

Like xf86GetOptValInteger(), except that value.realnum is used.

Bool xf86GetOptValFreq(OptionInfoPtr table, int token,
          OptFreqUnits expectedUnits, double *value)

Like xf86GetOptValInteger(), except that the value.freq data is returned. The frequency value is scaled to the units indicated by expectedUnits. The scaling is exact when the units were specified explicitly in the option's value. Otherwise, the expectedUnits field is used as a hint when doing the scaling. In this case, values larger than 1000 are assumed to have be specified in the next smallest units. For example, if the Option value is "10000" and expectedUnits is OPTUNITS_MHZ, the value returned is 10.

Bool xf86GetOptValBool(OptionInfoPtr table, int token, Bool *value)

This function is used to check boolean options (OPTV_BOOLEAN). If the function return value is FALSE, it means the option wasn't set. Otherwise *value is set to the boolean value indicated by the option's value. No option value is interpreted as TRUE. Option values meaning TRUE are "1", "yes", "on", "true", and option values meaning FALSE are "0", "no", "off", "false". Option names both with the "no" prefix in their names, and with that prefix removed are also checked and handled in the obvious way. *value is not changed when the option isn't present. It should normally be set to a default value before calling this function.

Bool xf86ReturnOptValBool(OptionInfoPtr table, int token, Bool def)

This function is used to check boolean options (OPTV_BOOLEAN). If the option is set, its value is returned. If the options is not set, the default value specified by def is returned. The option interpretation is the same as for xf86GetOptValBool().

int xf86NameCmp(const char *s1, const char *s2)

This function should be used when comparing strings from the config file with expected values. It works like strcmp(), but is not case sensitive and space, tab, and `_' characters are ignored in the comparison. The use of this function isn't restricted to parsing option values. It may be used anywhere where this functionality required.