[U-Boot] [PATCH 07/26] libfdt: Add a function to write a property placeholder

[Simon Glass]

Hi David,

On 28 January 2016 at 22:29, David Gibson <david at gibson.dropbear.id.au> wrote:
> On Thu, Jan 28, 2016 at 09:39:27AM -0700, Simon Glass wrote:
>> The existing function to add a new property to a tree being built requires
>> that the entire contents of the new property be passed in. For some
>> applications it is more convenient to be able to add the property contents
>> later, perhaps by reading from a file. This avoids double-buffering of the
>> contents.
>>
>> Add a new function to support this and adust the existing fdt_property() to
>> use it.
>>
>> Signed-off-by: Simon Glass <sjg at chromium.org>
>
> So, obviously such a patch should really go towards upstream libfdt.
>
> I'm happy enough with the concept, but I don't like the name.
>
> I'd prefer fdt_property_reserve() - the idea being that it reserves
> space for the property but doesn't fill it in.

Sounds good. I'll work up a patch. I tend to sync with upstream one a
quarter or so.

>
>> ---
>>
>>  include/libfdt.h    | 16 ++++++++++++++++
>>  lib/libfdt/fdt_sw.c | 16 ++++++++++++++--
>>  2 files changed, 30 insertions(+), 2 deletions(-)
>>
>> diff --git a/include/libfdt.h b/include/libfdt.h
>> index e48c21a..c3f37ee 100644
>> --- a/include/libfdt.h
>> +++ b/include/libfdt.h
>> @@ -1181,6 +1181,22 @@ static inline int fdt_property_cell(void *fdt, const char *name, uint32_t val)
>>  {
>>       return fdt_property_u32(fdt, name, val);
>>  }
>> +
>> +/**
>> + * fdt_property_val - add a new property and return a pointer to its value
>> + *
>> + * @fdt: pointer to the device tree blob
>> + * @name: name of property to add
>> + * @len: length of property value in bytes
>> + * @valp: returns a pointer to where where the value should be placed
>> + *
>> + * returns:
>> + *   0, on success
>> + *   -FDT_ERR_BADMAGIC,
>> + *   -FDT_ERR_NOSPACE, standard meanings
>> + */
>> +int fdt_property_val(void *fdt, const char *name, int len, void **valp);
>> +
>>  #define fdt_property_string(fdt, name, str) \
>>       fdt_property(fdt, name, str, strlen(str)+1)
>>  int fdt_end_node(void *fdt);
>> diff --git a/lib/libfdt/fdt_sw.c b/lib/libfdt/fdt_sw.c
>> index 320a914..9c1df3d 100644
>> --- a/lib/libfdt/fdt_sw.c
>> +++ b/lib/libfdt/fdt_sw.c
>> @@ -175,7 +175,7 @@ static int _fdt_find_add_string(void *fdt, const char *s)
>>       return offset;
>>  }
>>
>> -int fdt_property(void *fdt, const char *name, const void *val, int len)
>> +int fdt_property_val(void *fdt, const char *name, int len, void **valp)
>>  {
>>       struct fdt_property *prop;
>>       int nameoff;
>> @@ -193,7 +193,19 @@ int fdt_property(void *fdt, const char *name, const void *val, int len)
>>       prop->tag = cpu_to_fdt32(FDT_PROP);
>>       prop->nameoff = cpu_to_fdt32(nameoff);
>>       prop->len = cpu_to_fdt32(len);
>> -     memcpy(prop->data, val, len);
>> +     *valp = prop->data;
>> +     return 0;
>> +}
>> +
>> +int fdt_property(void *fdt, const char *name, const void *val, int len)
>> +{
>> +     void *ptr;
>> +     int ret;
>> +
>> +     ret = fdt_property_val(fdt, name, len, &ptr);
>> +     if (ret)
>> +             return ret;
>> +     memcpy(ptr, val, len);
>>       return 0;
>>  }
>>

Regards,
Simon