On 09/12/2012 01:28 PM, Guennadi Liakhovetski wrote: > Hi Stephen > > On Wed, 12 Sep 2012, Stephen Warren wrote: > >> On 09/11/2012 09:51 AM, Guennadi Liakhovetski wrote: >>> This patch adds a document, describing common V4L2 device tree bindings. >>> >>> Co-authored-by: Sylwester Nawrocki <s.nawrocki@xxxxxxxxxxx> >>> Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@xxxxxx> >> >> Overall, I think this looks pretty reasonable, so: ... >> >>> + clock-frequency = <50000000>; /* max clock frequency */ >>> + clock-output-names = "mclk"; >>> + }; >>> + >>> + port { >> ... >>> + ceu0_0: link@0 { >>> + reg = <0>; >>> + remote = <&csi2_2>; >>> + immutable; >> >> Did we decide "immutable" was actually needed? Presumably the driver for >> the HW in question knows the HW isn't configurable, and would simply not >> attempt to apply any configuration even if the .dts author erroneously >> provided some? > > Well, I've been thinking about this today. I think, bridge drivers will Sorry, I'm not sure what a "bridge" driver is; is it any v4l2 device? > call centrally provided helper functions to enumerate links inside ports. Presumably a given driver would only parse the ports/links of its own DT node, and hence would be able to provide a parameter to any helper function that indicated the same information that "immutable" would? > While doing that they will want to differentiate between links to external > devices with explicit configuration, and links to internal devices, whose > configuration drivers might be able to figure out themselves. How should a > driver find out what device this link is pointing to? Should it follow the > "remote" phandle and then check the "compatible" property? The word > "immutable" is a hint, that this is a link to an internal device, but it > might either be unneeded or be transformed into something more > informative. I would imagine that a given driver would only ever parse its own DT node; the far end of any link is purely the domain of the other driver. I thought that each link node would contain whatever hsync-active, data-lanes, ... properties that were needed to configure the local device? -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html