Re: [PATCH 1/3] of: base: add support to get machine compatible string

[Sudeep Holla]

On 23/11/16 07:49, Sekhar Nori wrote:
> On Tuesday 22 November 2016 09:16 PM, Sudeep Holla wrote:
> > Hi Sekhar,
> >
> > On 22/11/16 15:06, Sekhar Nori wrote:
> > > Hi Sudeep,
> > >
> > > On Tuesday 22 November 2016 04:23 PM, Sudeep Holla wrote:
> > > > On 22/11/16 10:41, Bartosz Golaszewski wrote:
> > > > > Add a function allowing to retrieve the compatible string of the root
> > > > > node of the device tree.
> > > >
> > > > Rob has queued [1] and it's in -next today. You can reuse that if you
> > > > are planning to target this for v4.11 or just use open coding in your
> > > > driver for v4.10 and target this move for v4.11 to avoid cross tree
> > > > dependencies as I already mentioned in your previous thread.
> > >
> > > I dont have your original patch in my mailbox, but I wonder if
> > > returning a pointer to property string for a node whose reference has
> > > already been released is safe to do? Probably not an issue for the root
> > > node, but still feels counter-intuitive.
> >
> > I am not sure if I understand the issue here. Are you referring a case
> > where of_root is freed ?
>
> Yes, right, thats what I was hinting at. Since you are giving up the
> reference to the device node before the function returns, the user can
> be left with a dangling reference.

Yes I agree.

> > Also I have seen drivers today just using this pointer directly, but
> > it's better to copy the string(I just saw this done in one case)
>
> Hmm, the reference is given up before the API returns, so I doubt
> copying it later is any additional benefit.

True.

> I suspect this is a theoretical issue though since root device node is
> probably never freed.

Indeed, not sure if it's worth adding additional code to release the nod
at all call sites.

--
Regards,
Sudeep