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Message-ID: <5b5833aa0512291323o1fe50d23m5f9fe6dc00f5f876@mail.gmail.com>
Date: Thu, 29 Dec 2005 17:23:52 -0400
From: Anderson Lizardo <anderson.lizardo@gmail.com>
To: Anderson Lizardo <anderson.lizardo@gmail.com>,
       Pierre Ossman <drzeus-list@drzeus.cx>,
       Anderson Briglia <anderson.briglia@indt.org.br>,
       Anderson Lizardo <anderson.lizardo@indt.org.br>,
       linux-omap-open-source@linux.omap.com, linux-kernel@vger.kernel.org,
       Carlos Eduardo Aguiar <carlos.aguiar@indt.org.br>,
       Russell King - ARM Linux <linux@arm.linux.org.uk>,
       Tony Lindgren <tony@atomide.com>, David Brownell <david-b@pacbell.net>
Subject: Re: [patch 0/5] Add MMC password protection (lock/unlock) support
In-Reply-To: <20051229200939.GA1113@flint.arm.linux.org.uk>
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On 12/29/05, Russell King <rmk+lkml@arm.linux.org.uk> wrote:
> On Thu, Dec 29, 2005 at 03:06:15PM -0400, Anderson Lizardo wrote:
> > On 12/15/05, Russell King <rmk+lkml@arm.linux.org.uk> wrote:
> > > Reading through the specs I have here, block sizes seem to be all over
> > > the place.  The MMC card specs seem to imply that any block size can
> > > be set, from 0 bytes to 2^32-1 bytes.
> > >
> > > The PXA MMC interface specification allows the block size to be anything
> > > from 1 to 1023 bytes, excluding CRC.  It is unclear whether a value of 0
> > > means 1024.
> > >
> > > The MMCI specification allows the block size to be specified as a power
> > > of two, from 1 to 2048 bytes, excluding CRC.
> >
> > By "allows" do you mean we can set the block size to arbitrary values
> > on MMCI too?
>
> No - that's not what I said.  I said "power of two, from 1 to 2048
> bytes excluding CRC."

Ah, so you meant "only allows", sorry for the confusion.

> > The MMC specification v4.1 is clear in one thing: the SET_BLOCKLEN
> > command should be issued prior to the actual LOCK_UNLOCK command with
> > *exactly* the password length + 2 bytes (which contains the operation
> > mode bits and the password length in bytes). The MMC password
> > unlocking (and other password operations, FWIW) doesn't work on the
> > OMAP host if the SET_BLOCKLEN command argument and the block size of
> > the data transfer itself do not match.
>
> Since passwords are limited to a maximum of 16 characters, this means
> that only passwords of length 2, 6, and 14 are possible with MMCI.
> All other passwords are invalid and/or impossible with this host.

What do you suggest in this case? So far the MMCI host seems the only
one (from those supported by mainline tree) that has such limitation.

--
Anderson Lizardo
Embedded Linux Lab - 10LE
Nokia Institute of Technology - INdT
Manaus - Brazil
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