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Date: Tue, 3 Nov 2015 22:18:12 +0100
From: Boris Brezillon <boris.brezillon@free-electrons.com>
To: Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>
Cc: Renaud Barbier <renaud.barbier@ge.com>, "linux-mtd@lists.infradead.org"
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Subject: Re: nand_flash_detect_onfi error
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On Tue, 3 Nov 2015 17:59:01 -0300
Ezequiel Garcia <ezequiel@vanguardiasur.com.ar> wrote:

> On 3 November 2015 at 17:25, Boris Brezillon
> <boris.brezillon@free-electrons.com> wrote:
> [..]
> >
> > Hm, sorry but I don't like this idea. ->cmdfunc() is not supposed to
> > retrieve any data before ->read_xxx() is called. I know some
> > controllers retrieve data ahead of time and then provide the previously
> > stored data when ->read_buf() is called, but that's not a good practice
> > to assume it will work this way on all controllers (actually I keep
> > thinking the sane implementations are those waiting for the
> > ->read_buf() call before starting retrieving the data from the NAND
> > chip).
> >
> 
> Right. We've discussed this in the past, and although I don't recall
> the details,
> I recall you were right.
> 
> In any case, I just wanted to mention that if Renaud is getting
> a read beyond the buffer, then probably the driver needs fixing.
> 

My bad, I thought the "read beyond the buffer" thing mentioned by
Renaud was something generic. Now I get your point, and I agree: it
should be fixed in the NAND controller driver, either by increasing the
read buffer or by reworking the implementation to delay data retrieval
until ->read_buf() is called.

-- 
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com