lkml.org 
[lkml]   [2016]   [May]   [17]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    From
    Date
    SubjectRe: [PATCH v2 6/6] doc: dt: Document the target root overlay method
    On Mon, May 16, 2016 at 3:18 PM, Pantelis Antoniou
    <pantelis.antoniou@konsulko.com> wrote:
    > Add a description of the target root overlay method to the overlay
    > documention file.
    >
    > Signed-off-by: Pantelis Antoniou <pantelis.antoniou@konsulko.com>
    > ---
    > Documentation/devicetree/overlay-notes.txt | 8 ++++++++
    > 1 file changed, 8 insertions(+)
    >
    > diff --git a/Documentation/devicetree/overlay-notes.txt b/Documentation/devicetree/overlay-notes.txt
    > index 6995fc1..3e8df30 100644
    > --- a/Documentation/devicetree/overlay-notes.txt
    > +++ b/Documentation/devicetree/overlay-notes.txt
    > @@ -104,6 +104,10 @@ If your board has multiple slots/places where a single overlay can work
    > and each slot is defined by a node, you can use the
    > of_overlay_create_target_index() method to select the target.
    >
    > +For overlays on probeable busses, use the of_overlay_create_target_root() method
    > +in which you supply a device node as a target root, and which all target
    > +references in the overlay are performed relative to that node.

    This needs a better explanation and an example. "Applying overlays to
    multiple places for probeable busses" is not sufficient. Describe what
    is the problem/flow, and then how does the implementation work. I
    don't think this problem is limited to probeable busses either. Not
    knowing the target to apply the overlay to is the same problem for
    connectors with non-probeable signals.

    I find a couple of things problematic with the implementation. There's
    no way to validate that an overlay should apply to a base node. If
    users just always make the target "/", then any overlay can apply to
    any location the nodes could apply anywhere. It requires a kernel
    change for every location you want to apply the overlay to. Maybe I
    don't understand the usecase.

    I feel like we are creating too many syntax's to apply overlays. I get
    that there are different usecases, but that doesn't necessarily mean
    the syntax needs to be different.

    > +
    > Overlay DTS Format
    > ------------------
    >
    > @@ -141,3 +145,7 @@ contains the information required to map from a phandle to a tree location.
    > Using a target index requires the use of a selector target on the call to
    > of_overlay_create_target_index(). I.e. passing an index of 0 will select the
    > target in the foo node, an index of 1 the bar node, etc.
    > +
    > +Note that when using the target root create method all target references must
    > +lie under the target root node. I.e. the overlay is not allowed to 'break' out
    > +of the root.

    That is not enforceable though, right?

    Rob

    \
     
     \ /
      Last update: 2016-05-17 15:21    [W:2.090 / U:0.196 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site