Limitations of the PMI

The following limitations exist in the PMI: 

   *  PMI does not provide a graphical interface. 

   *  PMI does not provide a means of accessing addresses that are 
      internal to the video controller and are not mappable into the CPU 
      space. 

   *  Save and Restore Hardware State Services have certain limitations 
      (see "Save and Restore State" in this chapter). 

   *  PMI does not provide the means to manipulate certain video 
      parameters outside the context of the SetMode section. 

      PMI does allow, and it requires, indirect management of all of the 
      parameters within the Mode Set sections. For example, there are no 
      services for the manipulation of the hardware cursor or RAMDAC 
      outside the context of a mode set. These services are an integral 
      part of the SetMode. 

      Programming of the monitor timing is considered a special case. It 
      is an integral part of the SetMode, but it also can be independently 
      invoked, if the .PMI file defines a SetMonitorTimings section. The 
      same is true for manipulation of the active display size. If the PMI 
      file contains a TuneDisplay section, this manipulation is offered 
      independently. 

   *  Port descriptions have some limitations, as follows: 

        -  Ports that require double or triple indirection cannot be 
           adequately described in the PMI language. 

        -  I/O addresses that serve as latches, or flip-flops, cannot be 
           successfully described. 

        -  There are no provisions for describing port addresses that 
           define different registers depending on the read or write 
           access. 

           These limitations have an influence on the level and success of 
           the adapter virtualization using the system-provided virtual 
           driver. See [TrapRegs] in PMI Sections.