• Tomi Valkeinen's avatar
    OMAPDSS: register only one display device per output · 1521653c
    Tomi Valkeinen authored
    We have boards with multiple panel devices connected to the same
    physical output, of which only one panel can be enabled at one time.
    Examples of these are Overo, where you can use different daughter boards
    that have different LCDs, and 3430SDP which has an LCD and a DVI output
    and a physical switch to select the active display.
    These are supported by omapdss so that we add all the possible display
    devices at probe, but the displays are inactive until somebody enables
    one. At this point the panel driver starts using the DSS, thus reserving
    the physcal resource and excluding the other panels.
    This is problematic:
    - Panel drivers can't allocate their resources properly at probe(),
      because the resources can be shared with other panels. Thus they can
      be only reserved at enable time.
    - Managing this in omapdss is confusing. It's not natural to have
      child devices, which may not even exist (for example, a daughterboard
      that is not connected).
    Only some boards have multiple displays per output, and of those, only
    very few have possibility of switching the display during runtime.
    Because of the above points:
    - We don't want to make omapdss and all the panel drivers more complex
      just because some boards have complex setups.
    - Only few boards support runtime switching, and afaik even then it's
      not required. So we don't need to support runtime switching.
    Thus we'll change to a model where we will have only one display device
    per output and this cannot be (currently) changed at runtime. We'll
    still have the possibility to select the display from multiple options
    during boot with the default display option.
    This patch accomplishes the above by changing how the output drivers
    register the display device. Instead of registering all the devices
    given from the board file, we'll only register one. If the default
    display option is set, the output driver selects that display from its
    displays. If the default display is not set, or the default display is
    not one of the output's displays, the output driver selects the first
    Signed-off-by: default avatarTomi Valkeinen <tomi.valkeinen@ti.com>