Enable enumeration of writeback connectors if both libdrm and the device
support it. The new Card::has_writeback() method report if the card
support writeback connectors.

Existing code that expect all connectors to model an output may be
confused by the sudden availability of new connectors. To handle this
issue,

- add a KMSXX_DISABLE_WRITEBACK_CONNECTORS environment variable to
  disable enumeration of writeback connectors, similarly to universal
  planes ; and

- ignore writeback connectors where no specific connector is requested
  (Card::get_first_connected_connector(),
  ResourceManager::reserve_connector() if no connector name is
  specified, and applications that use all connected outputs).

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

Add a new method to write the contents of a framebuffer to a file
descriptor. This can be used to capture frames from writeback
connectors.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

New templated conversion and test pattern code.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>

New pixel format code, from Python pixutils library.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>

Enables direct Python access to the framebuffer's buffer,
facilitating rapid image drawing capabilities.

Signed-off-by: LI Qingwu <Qing-wu.Li@leica-geosystems.com.cn>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>