Re: problems bringing up CF based file system (2.6.25)

Re: problems bringing up CF based file system (2.6.25)

[Rob Landley]

On Tuesday 27 May 2008 18:04:57 Adrian Bunk wrote:
> > I am not really worried about saving memory, I just am trying to
> > understand the reason the SCSI driver is included in the first place -
> > SCSI is a much heavier protocol than what is needed here - isn't it?
> >...
>
> ATAPI uses the SCSI command set, so using parts of the SCSI layer for
> implementing ATA support is not unreasonable.

The SCSI layer is actually _three_ layers (upper, mid, and lower).  It's a 
large and heavyweight solution that (last I checked) reimplements lots of 
stuff in the kernel's block layer.  It unnecessarily mixes together different 
types of transports so that plugging in a USB device can move where the 
kernel decides to put your compact flash device on the next boot, and then 
passes responsibility to udev to untangle the mess the kernel made by 
commingling different transport types in the first place.

Is it even possible to use just _parts_ of the SCSI layer, without sucking in 
the whole thing?

I think the fact it's called a "layer" is a bit of a hint, actually.  Don't 
embedded folks generally try to _avoid_ unnecessary layering, and pulling in 
large code libraries to perform a small task?

Rob
-- 
"One of my most productive days was throwing away 1000 lines of code."
  - Ken Thompson.
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Re: problems bringing up CF based file system (2.6.25)

[vb]

On Wed, May 28, 2008 at 8:17 PM, Rob Landley <rob-VoJi6FS/r0vR7s880joybQ@public.gmane.org> wrote:

>
> Is it even possible to use just _parts_ of the SCSI layer, without sucking in
> the whole thing?
>
> I think the fact it's called a "layer" is a bit of a hint, actually.  Don't
> embedded folks generally try to _avoid_ unnecessary layering, and pulling in
> large code libraries to perform a small task?
>


Good questions, it does seem quite excessive. Interestingly enough,
there is a platform option for the IDE driver as well
(CONFIG_BLK_DEV_PLATFORM): could it be the a better way to drive the
CF card in true IDE mode?

I must be missing something very basic, but can't get over this hurdle:

if I enable PATA platofrm, and define the card local bus/card in the
dts file, the card gets detected and properly recognized, but no
device seems to be created in /dev, so the card does not get mounted
when the board comes up.


If I enable CONFIG_BLK_DEV_PLATFORM instead (and no dts file
definitions), I can't get the probe function to be invoked, so the
card does not even get detected.

People, does anyone have CF card up and running in 2.6.25 - please,
share your secrets! :-)

Seriously, it is quite frustrating, I would really appreciate any extra hints,

TIA,
vadim

> Rob
> --
> "One of my most productive days was throwing away 1000 lines of code."
>  - Ken Thompson.
>
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