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Date:   Mon, 21 Oct 2019 09:44:35 +0200
From:   Boris Brezillon <boris.brezillon@collabora.com>
To:     masonccyang@mxic.com.tw
Cc:     bbrezillon@kernel.org, computersforpeace@gmail.com,
        dwmw2@infradead.org, frieder.schrempf@kontron.de,
        gregkh@linuxfoundation.org, juliensu@mxic.com.tw,
        linux-kernel@vger.kernel.org, linux-mtd@lists.infradead.org,
        marcel.ziswiler@toradex.com, marek.vasut@gmail.com,
        "Miquel Raynal" <miquel.raynal@bootlin.com>, richard@nod.at,
        tglx@linutronix.de, vigneshr@ti.com
Subject: Re: [PATCH RFC 2/3] mtd: rawnand: Add support Macronix Block
 Protection function
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On Mon, 21 Oct 2019 15:23:57 +0800
masonccyang@mxic.com.tw wrote:

> Hi Miquel,
> 
> 
> > > > > Then fill-in these two hooks from the manufacturer code, without   
> the
> > > > > postponed init.
> > > > >   
> > > > 
> > > > But in the final of nand_scan_tail(), mtd->_lock/_unlock will be
> > > > filled by NULL, right ?  
> > > 
> > > The NAND core should set mtd->_lock/_unlock() to NAND specific hooks   
> so
> > > that the MTD layer is abstracted and and drivers do not see it. Then,
> > > in the NAND helper, either there is no specific hook defined by a
> > > manufacturer driver and you return -ENOTSUPP, or you execute the
> > > defined hook.  
> > 
> > okay, patch specific manufacturer _lock/_unlock driver
> > in nand_manufacturer_init();
> > 
> > and in the final of nand_scan_tail()
> > if (!mtd->_lock)
> >  mtd->_lock = NULL;
> > if (!mtd->_unlock)
> >  mtd->_unlock = NULL;  
>  
> 
> I'm still considering of post_init() in nand_scan_tail() for
> MTD layer default call-back function replacement because
> there would be more call-back functions need it.
> i.e., 
> MTD->_lock/_unlokc
> MTD->_suspend/_resume

Again, that's something that needs to be abstracted so that both the
NAND manufacturer driver and the NAND controller driver can take
appropriate actions on suspend/resume operations.

> NTD->_point/_unpoint

->_point/_unpoint() are irrelevant for a NAND chip.

> ...
> 
> 
> actually, my patch series are including MTD->_locl/_unlock and 
> MTD->_suspend/_resume. how do you think ?

Miquel was suggesting to add nand_chip->{lock,unlock,is_locked}()
methods that would be implemented by the NAND manufacturer drivers, and
have generic wrappers implemented in nand_base.c:

static int nand_lock(struct mtd_info *mtd, loff_t ofs, uint64_t len)
{
	struct nand_chip *chip = mtd_to_nand(mtd);

	if (!chip->lock)
		return -ENOTSUPP;

	return chip->lock(chip, ofs, len);
}

...

If you do that, you won't need this post_init() hook.