Re: XD/smartmedia - how to implement it right?

[Alex Dubov <oakad@yahoo.com>]

--- On Sat, 11/28/09, Maxim Levitsky <maximlevitsky@gmail.com> wrote:

> From: Maxim Levitsky <maximlevitsky@gmail.com>
> Subject: Re: XD/smartmedia - how to implement it right?
> To: "Alex Dubov" <oakad@yahoo.com>
> Cc: "Jörn Engel" <joern@logfs.org>, "linux-kernel" <linux-kernel@vger.kernel.org>, arnd@arndb.de, tglx@linutonix.de
> Date: Saturday, November 28, 2009, 2:36 AM
> On Fri, 2009-11-27 at 23:22 -0800,
> Alex Dubov wrote: 
> > > 
> > > The "mtd uses blocking calls" argument I can
> help
> > > with.  For some other
> > > project I've added non-blocking calls to mtd[1].
> > > 
> > > Biggest problems I see are a) the userspace
> interface and
> > > b) allowing
> > > both raw flash access through MTD and block
> device access
> > > with an FTL.
> > > 
> > > [1] http://lists.infradead.org/pipermail/linux-mtd/2009-November/028065.html
> > > 
> > > Jörn
> > 
> > I actually tried several approaches to this problem
> and I think, I have a good idea about how to create a fully
> asynchronous mtd driver, which can handle different device
> models. Unfortunately, I had other commitments so I couldn't
> advance my mtd stuff.
> > 
> > Recently I was going to go back to it, but then I was
> asked to implement some additional functionality in rapidio
> subsystem, which I'll have to take care of first.
> 
> Hi, 
> 
> First of all, thank you very much for your contributions.
> Could you explain, why we need an asynchronous mtd driver?

Because it's the future. ;-)

> 
> Also, as I understand the command interface more and more,
> it seems that
> 'magically' xD card had same interface as standard NAND
> flash chip.
> 
> I think I can implement the driver for each controller just
> like an nand
> chip driver.
> 

xD spec, first of all, is about flash-based ordinary block devices.
All the hard problems are in good r/w FTL implementation, which is
currently mostly absent from the MTD.