On 09/20/2010 02:31 PM, Andrew Morton wrote:

On Mon, 20 Sep 2010 16:11:31 +0200
Ohad Ben-Cohen[off-list ref]  wrote:

   

quoted

Occasionally, drivers care about the value that idr associates with
their pointers.

Today we have idr_get_new_above() which allocates a new idr entry
above or equal to a given starting id, but sometimes drivers need to
force an exact value.

To overcome this small API gap, drivers are wrapping idr_get_new_above
and then either BUG_ON() or just call idr_remove() and returns -EBUSY
when idr allocates them an id which is different than their requested
value.

There are only a handful of users who need this (see below. especially
note the i2c comment :), but it might be nice to have such an API (a
bit less of code, and a bit less error prone).

Would something like the below be desirable/acceptable ?
     

It seems OK to me - it's an improvement over what we have now.

   

Looks ok to me also.  This is exactly what cxgb* needs.  IE the driver 
manages the ID space and never expects an idr insertion to fail because 
its already inserted.  That constitutes a driver bug (which is why the 
BUG_ON() is there :)).

Steve.