Writing Device Drivers

Creating and Updating Properties

To create a property for a driver, or to update an existing property, use an interface from the DDI driver update interfaces such as ddi_prop_update_int(9F) or ddi_prop_update_string(9F) with the appropriate property type. See Table 4–1 for a list of available property interfaces. These interfaces are typically called from the driver's attach(9E) entry point. In the following example, ddi_prop_update_string()creates a string property called pm-hardware-state with a value of needs-suspend-resume.

     /* The following code is to tell cpr that this device
     * needs to be suspended and resumed.
    (void) ddi_prop_update_string(device, dip,
         "pm-hardware-state", "needs-suspend-resume");

In most cases, using a ddi_prop_update() routine is sufficient for updating a property. Sometimes, however, the overhead of updating a property value that is subject to frequent change can cause performance problems. See prop_op() Entry Point for a description of using a local instance of a property value to avoid using ddi_prop_update().