linux-kernel - Re: [PATCH 2/2] drivers/core/of: Add symlink to device-tree from devices with an OF node

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Message-ID: <CAL_JsqKWJmt9e5hts1F6Yv_FqodJ6pkmqmxBqBp=Y33w+dPj9w@mail.gmail.com>
Date:	Tue, 17 Feb 2015 09:00:47 -0600
From:	Rob Herring <robherring2@...il.com>
To:	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	Grant Likely <grant.likely@...aro.org>,
	Olof Johansson <olof@...om.net>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH 2/2] drivers/core/of: Add symlink to device-tree from
 devices with an OF node

+GregKH

On Sun, Feb 15, 2015 at 9:59 PM, Benjamin Herrenschmidt
<benh@...nel.crashing.org> wrote:
> So I've been annoyed lately with having a bunch of devices such as i2c
> eeproms (for use by VPDs, server world !) and other bits and pieces that
> I want to be able to identify from userspace, and possibly provide
> additional data about from FW.
>
> Basically, it boils down to correlating the sysfs device with the OF
> tree device node, so that user space can use device-tree info such as
> additional "location" or "label" (or whatever else we can come up with)
> properties to identify a given device, or get some attributes of use
> about it, etc...
>
> Now, so far, we've done that in some subsystem in a fairly ad-hoc basis
> using "devspec" properties. For example, PCI creates them if it can
> correlate the probed device with a DT node. Some powerpc specific busses
> do that too.
>
> However, i2c doesn't and it would be nice to have something more generic
> since technically any device can have a corresponding device tree node
> these days.
>
> This patch achieves this by adding an "of_node" symlink to devices that
> have a non-NULL dev->of_node pointer.

Doesn't this need sysfs documentation?

> Signed-off-by: Benjamin Herrenschmidt <benh@...nel.crashing.org>

I don't mind applying, but this is Greg's code.

Rob

> ---
>  drivers/base/core.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
>
> diff --git a/drivers/base/core.c b/drivers/base/core.c
> index 97e2baf..61ef574 100644
> --- a/drivers/base/core.c
> +++ b/drivers/base/core.c
> @@ -469,6 +469,7 @@ static int device_add_attrs(struct device *dev)
>  {
>         struct class *class = dev->class;
>         const struct device_type *type = dev->type;
> +       struct device_node *of_node;
>         int error;
>
>         if (class) {
> @@ -493,6 +494,13 @@ static int device_add_attrs(struct device *dev)
>                         goto err_remove_dev_groups;
>         }
>
> +       of_node = dev_of_node(dev);
> +       if (of_node) {
> +               error = sysfs_create_link(&dev->kobj, &of_node->kobj, "of_node");
> +               if (error)
> +                       dev_warn(dev, "Error %d creating of_node link\n", error);
> +       }
> +
>         return 0;
>
>   err_remove_dev_groups:
>
>
>
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