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

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Date:   Tue, 22 Nov 2016 15:46:25 +0000
From:   Sudeep Holla <sudeep.holla@....com>
To:     Sekhar Nori <nsekhar@...com>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Kevin Hilman <khilman@...libre.com>,
        Michael Turquette <mturquette@...libre.com>,
        Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        Mark Rutland <mark.rutland@....com>,
        Peter Ujfalusi <peter.ujfalusi@...com>,
        Russell King <linux@...linux.org.uk>
Cc:     Sudeep Holla <sudeep.holla@....com>,
        LKML <linux-kernel@...r.kernel.org>,
        arm-soc <linux-arm-kernel@...ts.infradead.org>,
        linux-drm <dri-devel@...ts.freedesktop.org>,
        linux-devicetree <devicetree@...r.kernel.org>,
        Jyri Sarha <jsarha@...com>,
        Tomi Valkeinen <tomi.valkeinen@...com>,
        David Airlie <airlied@...ux.ie>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Robin Murphy <robin.murphy@....com>
Subject: Re: [PATCH 1/3] of: base: add support to get machine compatible
 string

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 ?

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)

> This is the code for reference:
>
> +int of_machine_get_model_name(const char **model)
> +{
> +       int error;
> +
> +       if (!of_node_get(of_root))
> +               return -EINVAL;
> +
> +       error = of_property_read_string(of_root, "model", model);
> +       if (error)
> +               error = of_property_read_string_index(of_root, "compatible",
> +                                                     0, model);
> +       of_node_put(of_root);
> +
> +       return error;
> +}
> +EXPORT_SYMBOL(of_machine_get_model_name);
>
> Thanks,
> Sekhar
>

-- 
Regards,
Sudeep