Re: [Qemu-arm] [Qemu-devel] [PATCH v6 2/8] device_tree: introduce load_device_tree_from_sysfs

[Rob Herring]

On Mon, Feb 1, 2016 at 10:22 AM, Eric Auger <address@hidden> wrote:
> Hi Rob,
> On 02/01/2016 05:15 PM, Rob Herring wrote:
>> On Mon, Feb 1, 2016 at 7:51 AM, Eric Auger <address@hidden> wrote:
>>> This function returns the host device tree blob from sysfs
>>> (/proc/device-tree). It uses a recursive function inspired
>>> from dtc read_fstree.
>>>
>>> Signed-off-by: Eric Auger <address@hidden>
>>>
>>> ---
>>> v5 -> v6:
>>> - fix some spelling mistakes
>>> - error_report + exit replaced by error_setg
>>> - const char *parent_node;
>>> - use g_strdup_printf instead of g_strjoin
>>> - add a doc comment for load_device_tree_from_sysfs
>>> v1 -> v2:
>>> - do not implement/expose read_fstree and load_device_tree_from_sysfs
>>>   if CONFIG_LINUX is not defined (lstat is not implemeted in mingw)
>>> - correct indentation in read_fstree
>>> - use /proc/device-tree symlink instead of /sys/firmware/devicetree/base
>>>   path (kernel.org/doc/Documentation/ABI/testing/sysfs-firmware-ofw)
>>> - use g_file_get_contents in read_fstree
>>> - introduce SYSFS_DT_BASEDIR macro and use strlen
>>> - exit on error in load_device_tree_from_sysfs
>>> - user error_setg
>>>
>>> RFC -> v1:
>>> - remove runtime dependency on dtc binary and introduce read_fstree
>>> ---
>>>  device_tree.c                | 99 
>>> ++++++++++++++++++++++++++++++++++++++++++++
>>>  include/sysemu/device_tree.h |  8 ++++
>>>  2 files changed, 107 insertions(+)
>>>
>>> diff --git a/device_tree.c b/device_tree.c
>>> index a9f5f8e..3797182 100644
>>> --- a/device_tree.c
>>> +++ b/device_tree.c
>>> @@ -17,6 +17,9 @@
>>>  #include <fcntl.h>
>>>  #include <unistd.h>
>>>  #include <stdlib.h>
>>> +#ifdef CONFIG_LINUX
>>> +#include <dirent.h>
>>> +#endif
>>>
>>>  #include "qemu-common.h"
>>>  #include "qemu/error-report.h"
>>> @@ -117,6 +120,102 @@ fail:
>>>      return NULL;
>>>  }
>>>
>>> +#ifdef CONFIG_LINUX
>>> +
>>> +#define SYSFS_DT_BASEDIR "/proc/device-tree"
>>
>> Use the sysfs path (/sys/firmware/device-tree/ IIRC) as this is just a
>> symlink to sysfs and /proc is considered the legacy path.
> I used the sysfs originally but I eventually found:
> https://www.kernel.org/doc/Documentation/ABI/testing/sysfs-firmware-ofw
> which states:
>
> "Userspace must not use the /sys/firmware/devicetree/base
> path directly, but instead should follow /proc/device-tree
> symlink. It is possible that the absolute path will change
> in the future, but the symlink is the stable ABI.
> "
>
> Do you confirm this statement is outdated.

Ah, no. My memory is just wrong. NM.

Rob