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Date: Wed, 16 Apr 2014 16:23:15 -0500
From: delicious quinoa <delicious.quinoa@...il.com>
To: Pantelis Antoniou <pantelis.antoniou@...sulko.com>
Cc: Grant Likely <grant.likely@...retlab.ca>,
Rob Herring <robherring2@...il.com>,
Stephen Warren <swarren@...dotorg.org>,
Matt Porter <matt.porter@...aro.org>,
Koen Kooi <koen@...inion.thruhere.net>,
Alison Chaiken <Alison_Chaiken@...tor.com>,
Dinh Nguyen <dinh.linux@...il.com>,
Jan Lubbe <jluebbe@...net.de>,
Alexander Sverdlin <alexander.sverdlin@....com>,
Michael Stickel <ms@...able.de>,
Guenter Roeck <linux@...ck-us.net>,
Dirk Behme <dirk.behme@...il.com>,
Sascha Hauer <s.hauer@...gutronix.de>,
Michael Bohan <mbohan@...eaurora.org>,
Ionut Nicu <ioan.nicu.ext@....com>,
Michal Simek <monstr@...str.eu>,
Matt Ranostay <mranostay@...il.com>,
"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
linux-kernel <linux-kernel@...r.kernel.org>,
Pete Popov <pete.popov@...sulko.com>,
Dan Malek <dan.malek@...sulko.com>,
Georgi Vlaev <georgi.vlaev@...sulko.com>
Subject: Re: [PATCH v3 0/7] Introducing (yet again) Device Tree Overlays
On Thu, Apr 3, 2014 at 3:40 PM, delicious quinoa
<delicious.quinoa@...il.com> wrote:
> On Fri, Mar 28, 2014 at 1:27 PM, delicious quinoa
> <delicious.quinoa@...il.com> wrote:
>> On Tue, Mar 18, 2014 at 4:55 PM, Pantelis Antoniou
>> <pantelis.antoniou@...sulko.com> wrote:
>>> The following patchset introduces Device Tree overlays, a method
>>> of dynamically altering the kernel's live Device Tree, along with
>>> a generic interface to use it in a board agnostic manner.
>>>
>>> It is dependent on Grant Likely's DT kobjectification patches located
>>> in his tree as queued for -next.
>>>
>>> It relies on the following previously submitted patches/patchsets:
>>>
>>> * OF: Add [__]of_find_node_by_full_name
>>> * OF: Utility helper functions for dynamic nodes
>>> * of: Make of_find_node_by_path() handle /aliases
>>>
>>> To compile overlays you need the DTC compiler patch
>>>
>>> * "dtc: Dynamic symbols & fixup support (v2)"
>>>
>>> Changes since V2:
>>> * Use of a configfs board agnostic overlay method
>>> * Use of per bus handlers instead of hardcoded behaviour
>>> * Optional target-path overlay target, which allows one to use standard
>>> DTBs without resolution options.
>>>
>>> Changes since V1:
>>>
>>> * Removal of any bits related to a specific board (beaglebone).
>>> * Introduced a platform agnostic interface using /proc/device-tree-overlay
>>> * Various bug fixes related to i2c device handling have been squashed in.
>>>
>>>
>>> Pantelis Antoniou (7):
>>> OF: Introduce Device Tree resolve support.
>>> OF: Introduce DT overlay support.
>>> OF: DT-Overlay configfs interface
>>> OF: platform: Add overlay bus handler
>>> OF: i2c: Add overlay bus handler
>>> OF: spi: Add overlay bus handler
>>> of: i2c: Export single device registration method
>>>
>>> .../devicetree/dynamic-resolution-notes.txt | 25 +
>>> Documentation/devicetree/overlay-notes.txt | 187 +++++
>>> drivers/base/platform.c | 99 ++-
>>> drivers/i2c/i2c-core.c | 186 +++--
>>> drivers/of/Kconfig | 24 +
>>> drivers/of/Makefile | 3 +
>>> drivers/of/configfs.c | 272 +++++++
>>> drivers/of/overlay.c | 895 +++++++++++++++++++++
>>> drivers/of/resolver.c | 376 +++++++++
>>> drivers/spi/spi.c | 345 +++++---
>>> include/linux/i2c.h | 10 +
>>> include/linux/of.h | 170 ++++
>>> 12 files changed, 2440 insertions(+), 152 deletions(-)
>>> create mode 100644 Documentation/devicetree/dynamic-resolution-notes.txt
>>> create mode 100644 Documentation/devicetree/overlay-notes.txt
>>> create mode 100644 drivers/of/configfs.c
>>> create mode 100644 drivers/of/overlay.c
>>> create mode 100644 drivers/of/resolver.c
>>
>> I can get a NULL pointer when I apply and remove an overlay and the
>> conditions are right. The overlay applies correctly. The crash is
>> when I do the rmdir. My overlay is:
>>
>> /dts-v1/;
>> /plugin/;
>> / {
>> fragment@0 {
>> target-path="/soc";
>> __overlay__ {
>> #address-cells = <1>;
>> #size-cells = <1>;
>> agpio0: agpio0 {
>> compatible = "altr,pio-1.0";
>> reg = <0xff210040 0x10>;
>
> Added some printks and got a bit further with debug. If I leave this
> as-is, the platform device has 2 resources. We get the NULL pointer in
> __release_resource() when releasing the first one (reg). If I remove
> this one line ('reg =') the crash goes away. So in this case, we are
> ok when releasing an irq resource but get a NULL pointer when removing
> a reg resource. Don't know why at this point.
The crash is confirmed on v4 patches as well. The immediate cause of the crash:
static int __release_resource(struct resource *old)
{
struct resource *tmp, **p;
p = &old->parent->child;
for (;;) {
tmp = *p; <===kablooey
...
when __release_resource() is called for the reg resource, it does 'p =
&olde->parent->child' and then crashes when it does 'tmp = *p'.
Root cause: It appears that there isn't any code in drivers/of/ that
eventually calls __request_resource() or __insert_resource() so the
resource's parents/sibling pointers are never initialized. Maybe I'm
missing some patches or something.
Alan Tull
aka
delicious quinoa
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