[prev in list] [next in list] [prev in thread] [next in thread] 

List:       kiobuf-io-devel
Subject:    Re: [Kiobuf-io-devel] DMAing to/from user space
From:       Jochen Strohbeck <strohbeck () gmx ! net>
Date:       2001-03-02 16:34:28
[Download RAW message or body]


"Stephen C. Tweedie" wrote:

> What driver?  kiobufs are just data containers.  The raw.c driver _is_
> a device driver which uses kiobufs.


Basically what I need:

'the application':

- allocate buffer ('malloc()')
- tell the driver about that buffer 
- tell the driver to start dma xfer
- ...

'the driver':

- lock this buffer
- find out everything about this buffer (start addr, no pages, ...)
  to build scatter/gather table for dma controller
- start dma
- tell the application that dma has finished
- ...

I'm purely guessing what these functions are used for in raw.c
(BTW: Is this code used to access raw block devices ? I always thought
that there was no way to bypass the disk cache in 2.2.x kernels ! But
now it's too late ...)

err = alloc_kiovec(1, &iobuf);
-> alloc kiobuf(s) ?

err = map_user_kiobuf(rw, iobuf, (unsigned long) buf, iosize);
-> lock buf(fer) ?

err = brw_kiovec(rw, 1, &iobuf, dev, b, sector_size);
-> copy data ?

unmap_kiobuf(iobuf);
-> unlock buf(fer) ?

free_kiovec(1, &iobuf);
-> free kiobuf(s) ? 


How can I find out the physical (bus) address(es) of the xfer buffer to
build dma lists for scatter/gather ? 


Please tell me if I'm in the wrong show ...

Jochen

_______________________________________________
Kiobuf-io-devel mailing list
Kiobuf-io-devel@lists.sourceforge.net
http://lists.sourceforge.net/lists/listinfo/kiobuf-io-devel

[prev in list] [next in list] [prev in thread] [next in thread]