Re: Zero copy between ISR, kernel and User

[Wink Saville <wink@saville.com>]

Stephen Hemminger wrote:
> On Tue, 26 Sep 2006 21:01:45 -0700
> Wink Saville <wink@saville.com> wrote:
>
>   
>> Hello,
>>
>> I would like to allow the transferring of data between ISR's, kernel and 
>> user code, without requiring copying. I envision allocating buffers in 
>> the kernel and then mapping them so that they appear at the same 
>> addresses to all code, and never being swapped out of memory.
>>
>> Is this feasible for all supported Linux architectures and is there 
>> existing code that someone could point me towards?
>>
>> Regards,
>>
>> Wink Saville
>>
>>     
>
> Your better off having application mmap a device, then transfer
> the data to there. Something like AF_PACKET.
>
>   
Is there some reason a kernel module can't mmap first, for instance I 
assume display drivers might do that? One of the reasons I need it to 
done in the kernel first is that data could come from the device or 
other entities before the application is running.

But I will study AF_PACKET handling.

Thanks,

Wink