On Mon, Mar 2, 2009 at 4:35 PM, Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote: > > OK. I think. > > - This approach will require a large number of edits each time an > attribute is added/removed. > > - otoh, removing nasty macros is always nice. > > - This approach will generate slower code (which doesn't matter > here). > > - Was it demonstrated that this approach generates less code? > It should generate less code, as compared to having two functions (show and store) per attribute, in which each function has about 4 lines and a local variable for the store functions (which is there for type validation). For both show and store functions, there still has to be code to get to the struct usb_xpad instance. As I was coding this interface, I found myself wishing for a macro-based system like module parameters have. For example, it would be nice to be able to do something like the following: DECLARE_SYSFS_INTERFACE(&xpad->dead_zone, uint, &check_dead_zone); which would create the needed show/store functions that worked with an unsigned int. The check_dead_zone function would be a validator function inside the module that would check the validity on a user-supplied value on store (in this case, to be sure it was at least 1024 below the stick limit) and return an error code if the value were out of range. Yes, the validator would be an extra function call, but this code doesn't run in an interrupt context, so the benefit of being able to centralize the functionality and simplify drivers might be worth the extra overhead. Mike -- Mike Murphy Ph.D. Candidate and NSF Graduate Research Fellow Clemson University School of Computing 120 McAdams Hall Clemson, SC 29634-0974 USA Tel: +1 864.656.2838 Fax: +1 864.656.0145 http://cirg.cs.clemson.edu/~mamurph -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
