Re: [RFC] SPI core -- revisited

[Vitaly Wool <vwool@dev.rtsoft.ru>]

Arjan van de Ven wrote:

> > Nothing's gonna work in DMA case if he kills the wrappers.
> >    
>
> how is that??
>  
These functions are not exactly *wrappers*, there's some little 
additional logic inside.
spi-pnx0105_atmel.c uses spi_pnx_msg_buff_t structure to embed physical 
and virtual address and length of the memory area allocated by 
consistent_alloc, so if we just get rid of the alloc/free functions, 
we'll copy wrong data from the userspace and nothing'll work.

Let's look at it from another point. When a read request comes from the 
userspace to spi-dev, spi-dev should allocate  memory and copy the user 
data in there. The problem is it is not (and shouldn't be) aware whether 
the transfer is gonna be DMA or not so spi-dev can't choose 
theappropriate method of memory allocation. Therefore it's reasonable to 
let algorithm provide routines to do that.

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