On Thu, Jul 04, 2013 at 10:45:40AM +0200, Sebastian Hesselbarth wrote:
On 07/04/13 10:33, Sascha Hauer wrote:
A componentized device never completes and it doesn't have to. A componentized device can start once there is a path from an input (crtc, i2s unit) to an output (connector, speaker).
Consider what happens with a supernode approach. Your board provides a devicetree which has a supernode with hdmi and lvds referenced. Now you build a kernel with the hdmi driver disabled. You would still expect the lvds port to be working without having the kernel wait for the supernode being complete.
Without supernode you can just start once you have everything between the crtc and lvds nodes. If later a hdmi device joins in then you can either notify the users (provided the DRM/KMS API supports it) or just ignore it until the DRM device gets reopened.
Sascha,
that is what it is all about. You assume you a priori know what devices will be required for the componentized device to successfully output a video stream.
We have shown setups where you don't know what is required. Cubox _needs_ lcd0 and hdmi-transmitter,
Then your Cubox devicetree has a link (that's how they call it in v4l2, a link doesn't necessarily is a direct connection but can have multiple devices in it) between lcd0 and hdmi.
olpc just needs lcd0 and has built-in hdmi in the SoC (IIRC).
And olpc has a link with lcd0 as the source and the builtin hdmi.
The driver needs to know what to wait for, and that is given by the DT super-node.
You need a source (described in the devicetree), a sink (also described in the devicetree) and a link between them, nothing more.
I consider kernels with missing drivers compared to what is given in the DT as broken setup.
What if your devicetree describes components not yet in mainline. Would you consider mainline kernels broken then?
Sascha