Messages in this thread | | | Date | Sun, 30 Mar 2008 21:29:06 +0900 (JST) | Subject | Re: [PATCH] atmel_spi: support zero length transfer (resend) | From | Atsushi Nemoto <> |
| |
On Sat, 29 Mar 2008 17:56:51 +0100, Haavard Skinnemoen <haavard.skinnemoen@atmel.com> wrote: > > Though some discussion about zero length transfer were raised by this > > patch last time, I think there were no explicit objection to this > > patch itself. > > Well, the patch doesn't seem to do any harm, but I can't see much of a > point to it either if zero-length transfers aren't going to be > allowed...
Well, some wired device might want long delay before first CLK edge. I think most device do not have such constraint, but ...
Anyway, SPI framework does not reject it. So I think the controller driver should accept it unless it is hard to support on that hardware.
> Also, if the length is zero, the driver will end up doing a memset with > length zero at some point. Is that allowed?
I believe memset() with zero length should be allowed. It seems ambiguous that dma_sync_single_for_device() with zero length is legal or not. Actually, it seems OK on ARM and AVR32.
--- Atsushi Nemoto
| |