Re: [PATCH v6 2/8] Documentation: of: Document graph bindings

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 




Hi Grant,

Am Freitag, den 07.03.2014, 18:27 +0000 schrieb Grant Likely:
> On Wed,  5 Mar 2014 10:20:36 +0100, Philipp Zabel <p.zabel@xxxxxxxxxxxxxx> wrote:
> > The device tree graph bindings as used by V4L2 and documented in
> > Documentation/device-tree/bindings/media/video-interfaces.txt contain
> > generic parts that are not media specific but could be useful for any
> > subsystem with data flow between multiple devices. This document
> > describes the generic bindings.
> > 
> > Signed-off-by: Philipp Zabel <p.zabel@xxxxxxxxxxxxxx>
> 
> See my comments on the previous version. My concerns are the handling of
> the optional 'ports' node and the usage of reverse links.

would this change address your concern about the reverse links? As the
preexisting video-interfaces.txt bindings mandate the reverse links, I
worry about introducing a second, subtly different binding. It should be
noted somewhere in video-interfaces.txt that the reverse links are
deprecated for the but still supported by the code for backwards
compatibility.

diff --git a/Documentation/devicetree/bindings/graph.txt b/Documentation/devicetree/bindings/graph.txt
index 1a69c07..eb6cae5 100644
--- a/Documentation/devicetree/bindings/graph.txt
+++ b/Documentation/devicetree/bindings/graph.txt
@@ -87,12 +87,13 @@ device {
 Links between endpoints
 -----------------------
 
-Each endpoint should contain a 'remote-endpoint' phandle property that points
-to the corresponding endpoint in the port of the remote device. In turn, the
-remote endpoint should contain a 'remote-endpoint' property. If it has one,
-it must not point to another than the local endpoint. Two endpoints with their
-'remote-endpoint' phandles pointing at each other form a link between the
-containing ports.
+Two endpoint nodes form a link between the two ports they are contained in
+if one contains a 'remote-endpoint' phandle property, pointing to the other
+endpoint. The endpoint pointed to should not contain a 'remote-endpoint'
+property itself. Which direction the phandle should point in depends on the
+device type. In general, links should be pointing outwards from central
+devices that provide DMA memory interfaces, such as display controller,
+video capture interface, or serial digital audio interface cores.
 
 device-1 {
         port {
@@ -104,8 +105,8 @@ device-1 {
 
 device-2 {
         port {
-                device_2_input: endpoint {
-                        remote-endpoint = <&device_1_output>;
+                device_2_input: endpoint { };
+                       /* no remote-endpoint, this endpoint is pointed at */
                 };
         };
 };

regards
Philipp

--
To unsubscribe from this list: send the line "unsubscribe devicetree" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html




[Index of Archives]     [Device Tree Compilter]     [Device Tree Spec]     [Linux Driver Backports]     [Video for Linux]     [Linux USB Devel]     [Linux PCI Devel]     [Linux Audio Users]     [Linux Kernel]     [Linux SCSI]     [XFree86]     [Yosemite Backpacking]
  Powered by Linux