lkml.org 
[lkml]   [2008]   [Jan]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: Question about DMA
On 01/27/2008 09:51 PM, Francis Moreau wrote:
> Hello,
>
> I have 2 questions regarding set_dma_addr(unsigned int channel,
> unsigned int addr) helper.
>
> 1/ Why does the function take only one address ? I would expect it
> to take both a source and a destination address for the dma controller
> to transfer data.

since your device is responsible for sending data from/to local memory. ISA dma
controller has only 2 registers -- 16-bit address to put incoming data to (get
outcoming from) + 8-bit nonincrementing page and 16-bit counter.

> 2/ The type of address parameter is an unsigned int. Why isn't it a dma_addr_t
> type ?

since isa dma controller can address up to 2^24 (16-bit address + 8-bit page)
bytes of memory, i.e. 16M.

Are you sure, you want use this API?



\
 
 \ /
  Last update: 2008-01-27 23:37    [W:0.216 / U:0.780 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site