[PATCH 2/9] Add dtget utility to read property values from device tree

[Simon Glass]

Hi David,

On Thu, Jul 28, 2011 at 5:22 AM, Simon Glass <sjg at chromium.org> wrote:
> Hi David,
>
> On Tue, Jul 19, 2011 at 3:34 PM, David Gibson
> <david at gibson.dropbear.id.au> wrote:
>> On Tue, Jul 05, 2011 at 12:02:50PM -0700, Simon Glass wrote:
>>> This simply utility makes it easy for scripts to read values from the device
>>> tree.
[snip]

>>> +static int show_data_for_key(const void *blob, const char *format, int type,
>>> +                          char *key)
>>> +{
>>> +     char *ptr, *prop;
>>> +     int node, guess_node = 0;
>>> +     const void *value;
>>> +     int len;
>>> +
>>> +     /* First extract the property from the end */
>>> +     ptr = strrchr(key, '/');
>>> +     if (!ptr) {
>>> +             fprintf(stderr, "No node found in key '%s'\n", key);
>>> +             return 5;
>>> +     }
>>
>> This is wrong.  properties do not have paths - they exist in a
>> separate namespace to nodes.  The node path and property name should
>> be supplied as separate parameters.  As well as being actually right,
>> it will greatly simplify this function's convoluted logic.
>
> Well yes, but I feel that it makes it harder to use also. My thinking
> with this was to try to make it easy to extract information. In my
> view:
>
> /lcd/width
>
> is better than
>
> /lcd width
>
> But this is the kind of discussion / feedback I was hoping to get as I
> am new to device trees. My thoughts:
>
> 1. / is not generally used in property names so there is no conflict
> 2. Neither is there any ambiguity
> 3. The 'complex' logic is there to make life easy for the poor
> hard-pressed user.
> 4. Creating the concept of a sort-of unified name space for a device
> tree property is probably not a bad idea.

I didn't hear back on this so I going to assume this is reasonable,
and submit another patch set with your other comments addressed. The
intent of the fdt seems clearly hierarchical to me. Hope this is ok.

Regards,
Simon

>
[more snip]

>> --
>> David Gibson                    | I'll have my music baroque, and my code
>> david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
>>                                | _way_ _around_!
>> http://www.ozlabs.org/~dgibson
>>
>