Messages in this thread | | | Date | Sat, 5 Sep 1998 21:10:47 +0200 | Subject | Re:Kernel programming Q: new aligned memory | From | Inaky Perez Gonzalez <> |
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>>>>> "Gerard" == Gerard Roudier <groudier@club-internet.fr> writes:
Hi
Gerard> Linux-2.0 kernel allocator does not provide such power of 2 Gerard> alignments.
I'm safe from that [excerpt from uusbd/README]
uusbd/README> I'm using 2.1.116 to run this.. 2.0.x won't uusbd/README> work, nor I intend too, as 2.2 is forthcoming shortly uusbd/README> (in stereo where available).
I don't plan to support 2.0 in the USB stack. Too much changes to be aware of and it is still too alpha for ppl to use it ...
However, u r right, most drivers must work :)
Gerard> [ 5 minutes code removed ]
>> The point is, if the size of the object is smaller then the >> alignment, ask for a chunk sized as the alignment, else the >> size. The rounding to the next power of two will do the same when >> allocating.
Gerard> If you want to align a object on a power of 2 greater than the Gerard> lowest power of 2 greater than the object size, then you just Gerard> want to waste memory, in my opinion. Do you really need that ?
Yes I do. The UHCI and OHCI USB controllers expect a lot of its structures to be aligned (most to 16, some at 32, one for OHCI at 256). It's neccessary in order to save a lot of bits in descriptors. However, it is also doable, as most OSs do power-of-two allocation. I see sense on it.
>> It's dirty, could be optimized, etc, etc ... but hey, I did it in >> five minutes :)
Gerard> Most of things we did in five minutes or less generally donnot Gerard> smell good. :-))
Well, it seems to work, so I won't worry anymore until it really needs my attention :]. There are funnier things to do!
Cheers
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