[SeaBIOS] Booting from USB thumbdrives, older drives boot, newer drives don't.

Dave Frodin dave at camp.se-eng.com
Sun Mar 4 20:05:14 CET 2012


Kevin/Paolo,
Our concern was that actual rotating media (e.g. USB-to-SATA adapter) may have
problems without the cdb_mode_sense_geom(). I hope to have my hands on one 
tomorrow to do some testing.

Dave

----- Original Message -----
> From: "Kevin O'Connor" <kevin at koconnor.net>
> To: "Dave Frodin" <dave at camp.se-eng.com>, "Paolo Bonzini" <pbonzini at redhat.com>
> Cc: seabios at seabios.org
> Sent: Sunday, March 4, 2012 11:49:30 AM
> Subject: Re: [SeaBIOS] Booting from USB thumbdrives, older drives boot, newer drives don't.
> 
> On Fri, Mar 02, 2012 at 03:10:33PM -0700, Dave Frodin wrote:
> > Here are my latest results.
> > The sg_modes command has a "-a" option to dump out all of the
> > supported page codes
> >    - it reports that none of the thumbdrives (tested 9) support
> >    page code = 4
> >    - it reports that most of the thumbdrives (tested 9) support
> >    page code = 5
> >    - it commented that page code 5 is obsolete
> 
> Thanks Dave.  I appreciate your detailed analysis.
> 
> The call to cdb_mode_sense_geom() was only recently added.  I'm
> inclined to just remove the call.  Paolo, is there a use case where
> having the "physical" chs info is important?  SeaBIOS should generate
> good "virtual" chs info regardless, and the underlying "physical"
> info
> is only exported in a couple of places.
> 
> > Marc suggested that I leave the page_code set to 4 in order to
> > preserve functionality for drives that actually report valid CHS
> > geometry, and to add code that would clear the stall from the USB
> > controller and thumbdrive.
> 
> The SeaBIOS code really should know how to clear a stall.  However,
> it's a bit of a pain to do that in the general case.  (In the general
> case, we'd need to support clearing the stall from 16bit mode, which
> would require the ability to send control messages to the drive in
> 16bit mode.)
> 
> >   2) Is there any way to differentiate between a USB thumbdrive and
> >      a USB-to-SATA adapter?
> 
> I don't know of a way to detect it, but I haven't looked closely.
> 
> -Kevin
> 



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