[patch 1/5] Staging: VME Framework for the Linux Kernel

Martyn Welch martyn.welch at gefanuc.com
Mon Aug 10 16:40:07 UTC 2009

Emilio G. Cota wrote:
> Emilio G. Cota wrote:
>> I've had a closer look; it seems to me that most of it is unnecessary;
>> there's no show those lists to a driver. I'd just provide a single
>> 'do_dma(attributes)' call that sleeps until it's done (or similar).
> s/there's no show/there's no point in showing/
> Basically the driver simply shouldn't care about these DMA
> lists. It just wants to get the work done, no matter how.
> E.
I have provided helper functions to aid with filling out structures that 
define the attributes, these are then pointed to by a generic DMA 
transfer structure. Bar the helper functions to aid in completing these 
commonly filled structures, at this level I can't see much difference. 
However rather than targeting a the "single shot" operation of the DMA 
controller I have provided the ability for the driver writer to use the 
link-list mode.

If the driver writer wants a "single shot" effect, there's little 
overhead in creating a one item link-list and executing it. However, 
without support for this mode the author is stuck with single shot 
transfers.  If the author wants to perform scatter gather type 
transfers, without this functionality in the API - which is supported by 
all the bridges I have seen - he won't be able to easily avail himself 
of this functionality and get "work done".


Martyn Welch MEng MPhil MIET (Principal Software Engineer)   T:+44(0)1327322748
GE Fanuc Intelligent Platforms Ltd,        |Registered in England and Wales
Tove Valley Business Park, Towcester,      |(3828642) at 100 Barbirolli Square,
Northants, NN12 6PF, UK T:+44(0)1327359444 |Manchester,M2 3AB  VAT:GB 927559189

More information about the devel mailing list