The eCos Component Writer's Guide
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# doc

## Name

Property doc -- The location of online-documentation for a configuration option.

## Synopsis

    cdl_option <name> {
        doc <URL;>
        …
    }

## Description

Users can only be expected to manipulate configuration options sensibly if they are given sufficient information about these options. There are three properties which serve to explain an option in plain text: the display property gives a textual alias for an option, which is usually more comprehensible than something like `CYGPKG_LIBC_TIME_ZONES`; the description property gives a longer description, typically a paragraph or so; the doc property specifies the location of additional on-line documentation related to a configuration option. In the context of a graphical tool the display string will be the primary way for users to identify configuration options; the description paragraph will be visible whenever the option is selected; the on-line documentation will only be accessed when the user explicitly requests it.

The documentation may be an absolute URL, but more generally the on-line documentation will be shipped with the package and can be accessed via a relative URL. If the package follows the directory layout conventions then the configuration tools will search for the specified html file first in the `doc` subdirectory of the package, then relative to the package directory itself. The URL may contain a `#` character to specify an anchor within a page.

Warning
At the time of writing the eCos packages in the standard distribution do not conform to the directory layout conventions when it comes to the documentation. Instead of organizing the documentation on a per-package basis and placing it in the corresponding `doc` sub-directories, all the documentation is kept in a central location. This should get addressed in a future release of the system. Third party component writers should follow the layout conventions.

## Example

    cdl_package CYGPKG_KERNEL {
        display       "eCos kernel"
        doc           ref/ecos-ref.4.html
        include_dir   cyg/kernel
        description   "
            This package contains the core functionality of the eCos
            kernel. It relies on functionality provided by various HAL
            packages and by the eCos infrastructure. In turn the eCos
            kernel provides support for other packages such as the device
            drivers and the uITRON compatibility layer."
        …
    }

## See Also

Properties description and display.

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