AW: DOC vs. IDE

[Richard A. Smith]

On Wed, 23 Oct 2002 14:28:23 -0600 (MDT), Ronald G Minnich wrote:

> On Wed, 23 Oct 2002, Christopher Bergeron wrote:
> 
> > That actually sounds like a brilliant idea.  I wonder if anyone on the
> > list can confirm performance... does the CFcard appear as a standard IDE
> > disk or is there a driver or anything necessary?
> 
> we're doing it here on the PCM-5823-A2 geode cards. We use CF as /dev/hdc,
> there is no /dev/hd1. Works fine.
> 

I'll pipe in a little bit of personal experience here.  If you are
_just_ using a CF with an IDE adapter then all is well and things
will work great.

During bringup and debug though its nice to have a big HD with a full
linux distribution on on it so you can develope on your target.

However if you are using a CF _and_ a normal IDE drive you may run
into a gotcha.  In the 2.2 linux IDE code there are clauses that if a
CF device is dectected on hda it will NOT probe for hdb.  Same goes
for hdc and hdd.  There is no output telling you its skipping it
either.  Apparently there were some early CF devices that did some
funky stuff with the diag signal (drive dection) and Andre (the 2.2
IDE maintainer) chose to blacklist all CF devices.

The fix is to feed the kernel some parameter like ide0=flash or
something similar to make it go ahead and probe.

I haven't looked at the 2.4.x IDE code so I don't know if it carried
over or not. 

But if you mysteriously don't have an hdb with a CF hooked up in your
system go check the IDE probing code before you pull you hair out
trying to figure out whats wrong with your hardware like I did.

--
Richard A. Smith                         Bitworks, Inc.               
rsmith at bitworks.com               479.846.5777 x104                        
Sr. Design Engineer        http://www.bitworks.com