(Fwd) Re: DOSFS bug fixes, IDE drivers and sample released

[Eugeny S. Mints]

On Mon, 3 Mar 2003, Thomas Doerfler wrote:

>
> ------- Forwarded message follows -------
> From:           	"Thomas Doerfler" <Thomas.Doerfler at imd-systems.de>
> Organization:   	IMD
> To:             	Chris Caudle <chris at chriscaudle.org>
> Date sent:      	Mon, 03 Mar 2003 09:01:38 +0100
> Subject:        	Re: DOSFS bug fixes, IDE drivers and sample released
> Copies to:      	Thomas Doerfler <Thomas.Doerfler at imd-systems.de>
> Priority:       	normal
>
>
>
> > On Sunday 02 March 2003 9:48 am, Joel Sherrill wrote:
> > > >filed as PR 367/368/369 in the GNATS system, see:
> >
> > Does the driver filed in PR 368 support DMA transfer yet, or programmed I/O
> > only?
> >
>
> It is really a minimal implementation, supporting PIO mode.
> Actually I am not so aware about various IDE transfer modes,
> the integration of DMA into the PC architecture an so on, my
> goal was to implement at least basic harddisc support.

Actually the answer is the following: DMA and POI modes are
entities which belong to generic high level ATA driver
implemented in ata.c file. In other words wether the data
will be transferred in PIO or DMA mode depends on ATA
commands issued. In general, low level IDE drivers (as
Thomas drivers written for i386 and mbx8xx) just "pass" ATA commands to an
IDE chip just by providing ability for writing any data to a
chip registers. In addition to the basic
functionality described above, current IDE drivers have
several routines for optimization of data read/write in PIO
mode (*_ide_read_block/*pc386_ide_write_block).

So, any low level IDE driver has ability to support PIO and
DMA modes by definition (but of course current low IDE
drivers may need some update for DMA support) and the issue
depends on generic ATA driver implementaion. Unfortunately, current ATA
driver implementation supports only PIO mode, but from the
beggining was designed to allow easy extension (I
mean addition of new ATA commands). So, generic ATA driver
should be modified for DMA mode support.

>
> So here is a lot of space to improve things :-)

Agree:)))

Hope, this helps,
                        Eugeny


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Eugeny S. Mints
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