On 07/03/13 13:43, Inki Dae wrote:
I do not understand why you keep referring to the SoC dtsi. Im my
example, I said that it is made up and joined from both SoC dtsi and
board dts.
So, of course, lcd controller nodes and dcon are part of dove.dtsi
because they are physically available on every Dove SoC.
Also, the connection from lcd0 to the external HDMI encoder node
is in the board dts because you can happily build a Dove SoC board
with a different HDMI encoder or with no encoder at all.
The video-card super node is not in any way specific to DRM and
In case of fbdev, framebuffer driver would use lcd0 or lcd1 driver, or lcd0
and lcd1 drivers which are placed in drivers/video/backlight/.
And let's assume the following:
On board A
Display controller ------------- lcd 0
On board B
Display controller ------------- lcd 1
On board C
Display controller ------------- lcd 0 and lcd 1
Without the super node, user could configure Linux kernel through menuconfig
like below;
board A: enabling lcd 0, and disabling lcd 1,
board B: disabling lcd 0, and enabling lcd 1,
board C: enabling lcd 0 and lcd 1.
All we have to do is to configure menuconfig to enable only drivers for
certain board. Why does fbdev need the super node? Please give me comments
if there is my missing point.
I assume when you say "configure menuconfig" you mean
"create a CONFIG_DISPLAY_CONTROLLER_AS_USED_ON_BOARD_A,
CONFIG_DISPLAY_CONTROLLER_AS_USED_ON_BOARD_B, ..." ?
This finally will require you to have
(a) #ifdef mess for every single board _and_ driver above
(b) new CONFIG_.._BOARD_D plus new #ifdefs in fbdev driver for every
new board
(c) A new set of the above CONFIG_/#ifdef for DRM driver
This can also be done with device_tree and supernode approach,
so for your example above:
BoardA.dts:
video { card0 { video-devices = <&lcd0>; }; };
BoardB.dts:
video { card0 { video-devices = <&lcd1>; }; };
BoardC.dts:
video { card0 { video-devices = <&lcd0 &lcd1>; }; };
and in the driver your are prepared for looping over the video-devices
property and parsing the compatible string of the nodes passed.
Sebastian
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