Subject: Re: qtopia
To: Garrett D'Amore <>
From: Jason Thorpe <>
List: tech-kern
Date: 06/06/2006 10:55:09
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.

-- thorpej