On Thursday 15 November 2012, Rob Clark wrote:
On Thu, Nov 15, 2012 at 3:19 AM, Arnd Bergmann arnd@arndb.de wrote:
On Tuesday 13 November 2012, Russell King - ARM Linux wrote:
You're missing something; that is one of the greatest powers of open source. The many eyes (and minds) effect. Someone out there probably has a solution to whatever problem, the trick is to find that person. :)
I think we have a working solution for this for ARM. It won't be suitable for every arch, where they have 8-bit and 16-bit registers able to be allocated by the compiler, but for architectures where the minimum register size is 32-bit, what we have below should work.
I don't mind at all adding the extension to ARM, and I think it's pretty cool that you guys actually found a working solution.
The part that worries me is that we are making architecture independent code depend on a clever hack that may or may not be possible to implement on a given architecture, and that most architecture maintainers wouldn't know how to implement correctly even if it's possible.
I could always send a 3rd version with a comment smashed on about why that works if you think this is a problem..
Comments are always good, so I'd surely like to see those get added. As I said, I don't have any objections to the addition of your patch to the ARM code, which sounds useful to have.
I still haven't heard a conclusive argument why we need to use get_user() rather than copy_from_user() in the DRM code. Is this about a fast path where you want to shave off a few cycles for each call, or does this simplify the code structure, or something else?
Arnd