Christos Zoulas wrote:
> In article <2C639E24-25C7-4083-B000-973CC36DD05C@shagadelic.org>,
> Jason Thorpe  <thorpej@shagadelic.org> wrote:
>   
>> On Jun 6, 2006, at 10:29 AM, Garrett D'Amore wrote:
>>
>>     
>>> That's not a bad idea.  Is there an example for passing properties in
>>> ioctls, or is there another way to exchange this data?
>>>       
>> proplib is new enough that it's not being used for this purpose yet.   
>> However, it's perfect for the "capabilities supported" / "options  
>> enabled" kind of thing, where the list might grow in the future  
>> (beyond 32-bits worth of features, perhaps).
>>
>> As for how to pass it back and forth, prop_dictionary_externalize()  
>> before sending it across the boundary, prop_dictionary_internalize()  
>> when receiving it from across the boundary.  Maybe we should even  
>> make a generic ioctl argument:
>>
>> struct plistref {
>> 	const char *plist_ptr;
>> 	size_t plist_len;
>> };
>>
>> Then your hypothetical "get capabilities" ioctl could be:
>>
>> #define	FOOGETCAPS	_IOWR('f', 0, struct plistref)
>>
>> and your "get properties" / "set properties" could be:
>>
>> #define	FOOSETPROPS	_IOW('f', 1, struct plistref)
>> #define	FOOGETPROPS	_IOWR('f', 2, struct plistref)
>>
>> We could probably even have a generic helper function in the kernel,  
>> and a corresponding one in userspace, that took care of the temporary  
>> buffer allocation, etc.
>>
>>     
>
> shouldn't the pointer be const void *?
>   

I wouldn't think so.  As a "packed" property list, it really is a
character array.  Making it void * would just mean having to add casting
later to do the pointer arithmetic necessary to unpack it.

    -- Garrett
> christos
>   


-- 
Garrett D'Amore, Principal Software Engineer
Tadpole Computer / Computing Technologies Division,
General Dynamics C4 Systems
http://www.tadpolecomputer.com/
Phone: 951 325-2134  Fax: 951 325-2191