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Message-ID: <20110408165252.GB27556@angua.secretlab.ca>
Date: Fri, 8 Apr 2011 09:52:52 -0700
From: Grant Likely <grant.likely@...retlab.ca>
To: Andres Salomon <dilinger@...ued.net>
Cc: devicetree-discuss@...ts.ozlabs.org, Daniel Drake <dsd@...top.org>,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/4] of: rework of_attach_node, removing CONFIG_OF_DYNAMIC
On Thu, Mar 17, 2011 at 05:32:33PM -0700, Andres Salomon wrote:
> Remove the OF_DYNAMIC config option, which makes of_attach_node/of_detach_node
> available without a specific config option. CONFIG_OF_DYNAMIC wasn't actually
> being used by anything, as the drivers which made use of of_attach_node
> weren't depending upon or selecting it.
>
> This also reworks of_attach_node to honor node ordering by time, rather than
> creating the allnext/sibling list in reverse order. This has a number of
> ramifications worth mentioning:
>
> - 'last_child' is added to the device_node struct, and used to figure out
> where a node should be added in the tree. This will take the place of
> the 'next' field.
> - 'allnodes' is no longer used. It is assumed that the parent node is already
> attached to the tree. What this really means is a simple assignment of
> "allnodes = root_node;" prior to calling of_attach_node(root_node).
> - The sibling list is guaranteed to retain order by insertion (later
> insertions showing up later in the list).
> - There are no similar guarantees for the allnext list with respect to
> parents, their children, and their siblings. While siblings are
> guaranteed to be ordered by time, children may come before a sibling,
> or after. That is, one ordering of the allnext list may be: "/", "/pci",
> "/isa", "/pci/foo", "/pci/bar". Another perfectly valid ordering (and
> this *will* happen depending upon how insertions are done) is: "/",
> "/pci", "/pci/foo", "/pci/bar", "/isa". The only thing that is
> guaranteed is that the sibling list will be "/pci", "/isa" (if "/isa"
> is added later), and that "/pci" will come before "/isa" in the allnext
> list.
>
> Signed-off-by: Andres Salomon <dilinger@...ued.net>
Hi Andres, comment below.
> ---
> drivers/of/Kconfig | 4 ----
> drivers/of/base.c | 47 ++++++++++++++++++++++++++++++++---------------
> include/linux/of.h | 5 ++---
> 3 files changed, 34 insertions(+), 22 deletions(-)
>
> diff --git a/drivers/of/Kconfig b/drivers/of/Kconfig
> index d06a637..ba90122 100644
> --- a/drivers/of/Kconfig
> +++ b/drivers/of/Kconfig
> @@ -26,10 +26,6 @@ config OF_EARLY_FLATTREE
> config OF_PROMTREE
> bool
>
> -config OF_DYNAMIC
> - def_bool y
> - depends on PPC_OF
> -
> config OF_ADDRESS
> def_bool y
> depends on !SPARC
> diff --git a/drivers/of/base.c b/drivers/of/base.c
> index 710b53b..9e94267 100644
> --- a/drivers/of/base.c
> +++ b/drivers/of/base.c
> @@ -849,27 +849,46 @@ int prom_update_property(struct device_node *np,
> return 0;
> }
>
> -#if defined(CONFIG_OF_DYNAMIC)
> -/*
> - * Support for dynamic device trees.
> - *
> - * On some platforms, the device tree can be manipulated at runtime.
> - * The routines in this section support adding, removing and changing
> - * device tree nodes.
> - */
> -
> /**
> * of_attach_node - Plug a device node into the tree and global list.
> */
> void of_attach_node(struct device_node *np)
> {
> + struct device_node *parent;
> unsigned long flags;
>
> + parent = np->parent;
> + if (!parent)
> + return;
> +
> write_lock_irqsave(&devtree_lock, flags);
> - np->sibling = np->parent->child;
> - np->allnext = allnodes;
> - np->parent->child = np;
> - allnodes = np;
> + if (parent->child) {
> + /*
> + * We have at least 1 sibling, and last_child points to the
> + * last one that we've inserted.
> + *
> + * After insertion, the current node will be the last sibling
> + * in the sibling list (maintaining tree order), but will come
> + * before any siblings' children in the allnext list. That
> + * holds true so long as the device tree is generated in a
> + * depth-first fashion. Children added later may screw with
> + * the allnext ordering, but siblings are always guaranteed to
> + * remain in the order in which they were added.
> + */
> + parent->last_child->sibling = np;
> + np->allnext = parent->last_child->allnext;
> + parent->last_child->allnext = np;
> +
> + } else {
> + /*
> + * This node is an only child. Allnext descends into the
> + * child nodes from the parent.
> + */
> + parent->child = np;
> + np->allnext = parent->allnext;
> + parent->allnext = np;
> + }
> + parent->last_child = np;
Hmmm... this screams to me that it shouldn't be open-coded. Instead,
it really should be using list_head. Unfortunately, that is a more
complex change, but I don't think I want to open code a new list
implementation.
blech. I need to think about that more.
g.
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