Re: [PATCH 1/2] of: implement of_append_property

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

On 09.08.22 09:26, Marco Felsch wrote:
> Hi Ahmad,
> 
> On 22-08-09, Ahmad Fatoum wrote:
>> board code fix up the device tree for OS consumption. Sometimes it's
>> useful for the fixup to append onto an existing property.
>> Add a helper that simplifies this.
> 
> do you have a particular use-case for this?

I have two boards that aren't yet upstream with board support
code using this:

 - One uses it to append onto the model string information about the
   SoM revision

 - One parses a format from an EEPROM and fixes up the device tree
   accordingly. If it encounters the same tag twice, it appends
   onto the previous property instead of overwriting.

I figured if I needed it twice, it can be useful to others as well.
The tests should ensure it doesn't bit rot until hardware is
finalized and board support is upstreamed.

Cheers,
Ahmad 


> 
> Regards,
>   Marco
> 
>> Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
>> ---
>>  drivers/of/base.c | 36 ++++++++++++++++++++++++++++++++++++
>>  include/of.h      |  8 ++++++++
>>  2 files changed, 44 insertions(+)
>>
>> diff --git a/drivers/of/base.c b/drivers/of/base.c
>> index 101b2f74c74f..0893bdf3e04f 100644
>> --- a/drivers/of/base.c
>> +++ b/drivers/of/base.c
>> @@ -2321,6 +2321,42 @@ int of_set_property(struct device_node *np, const char *name, const void *val, i
>>  	return 0;
>>  }
>>  
>> +int of_append_property(struct device_node *np, const char *name, const void *val, int len)
>> +{
>> +	struct property *pp;
>> +	void *buf = NULL;
>> +	int orig_len = 0;
>> +
>> +	if (!np)
>> +		return -ENOENT;
>> +
>> +	pp = of_find_property(np, name, NULL);
>> +	if (pp) {
>> +		buf = pp->value;
>> +		orig_len = pp->length;
>> +	}
>> +
>> +	buf = realloc(buf, orig_len + len);
>> +	if (!buf)
>> +		return -ENOMEM;
>> +
>> +	memcpy(buf + orig_len, val, len);
>> +
>> +	if (pp) {
>> +		pp->value = buf;
>> +		pp->length += len;
>> +
>> +		if (pp->value_const) {
>> +			memcpy(buf, pp->value_const, orig_len);
>> +			pp->value_const = NULL;
>> +		}
>> +	} else {
>> +		pp = __of_new_property(np, name, buf, len);
>> +	}
>> +
>> +	return 0;
>> +}
>> +
>>  int of_property_sprintf(struct device_node *np,
>>  			const char *propname, const char *fmt, ...)
>>  {
>> diff --git a/include/of.h b/include/of.h
>> index c65cef5a5a7c..97b4b3dd79bd 100644
>> --- a/include/of.h
>> +++ b/include/of.h
>> @@ -131,6 +131,8 @@ extern struct device_node *of_get_cpu_node(int cpu, unsigned int *thread);
>>  
>>  extern int of_set_property(struct device_node *node, const char *p,
>>  			const void *val, int len, int create);
>> +extern int of_append_property(struct device_node *np, const char *p,
>> +			      const void *val, int len);
>>  extern struct property *of_new_property(struct device_node *node,
>>  				const char *name, const void *data, int len);
>>  extern struct property *of_new_property_const(struct device_node *node,
>> @@ -515,6 +517,12 @@ static inline int of_set_property(struct device_node *node, const char *p,
>>  	return -ENOSYS;
>>  }
>>  
>> +static inline int of_append_property(struct device_node *np, const char *p,
>> +				      const void *val, int len)
>> +{
>> +	return -ENOSYS;
>> +}
>> +
>>  static inline struct property *of_new_property(struct device_node *node,
>>  				const char *name, const void *data, int len)
>>  {
>> -- 
>> 2.30.2
>>
>>
>>
> 


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