linux-kernel - Re: [PATCH v3 3/4] mtd: rawnand: Add support manufacturer specific suspend/resume operation

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Date:   Wed, 11 Mar 2020 09:01:01 +0100
From:   Boris Brezillon <boris.brezillon@...labora.com>
To:     masonccyang@...c.com.tw
Cc:     allison@...utok.net, bbrezillon@...nel.org,
        frieder.schrempf@...tron.de, juliensu@...c.com.tw,
        linux-kernel@...r.kernel.org, linux-mtd@...ts.infradead.org,
        miquel.raynal@...tlin.com, rfontana@...hat.com, richard@....at,
        s.hauer@...gutronix.de, stefan@...er.ch, tglx@...utronix.de,
        vigneshr@...com, yuehaibing@...wei.com
Subject: Re: [PATCH v3 3/4] mtd: rawnand: Add support manufacturer specific
 suspend/resume operation

On Wed, 11 Mar 2020 14:13:57 +0800
masonccyang@...c.com.tw wrote:

> Hi Boris,
> 
> > > > ---
> > > >  drivers/mtd/nand/raw/nand_base.c | 11 ++++++++---
> > > >  include/linux/mtd/rawnand.h      |  4 ++++
> > > >  2 files changed, 12 insertions(+), 3 deletions(-)
> > > > 
> > > > diff --git a/drivers/mtd/nand/raw/nand_base.c   
> b/drivers/mtd/nand/raw/nand_base.c
> > > > index 769be81..b44e460 100644
> > > > --- a/drivers/mtd/nand/raw/nand_base.c
> > > > +++ b/drivers/mtd/nand/raw/nand_base.c
> > > > @@ -4327,7 +4327,9 @@ static int nand_suspend(struct mtd_info *mtd)
> > > >     struct nand_chip *chip = mtd_to_nand(mtd);
> > > > 
> > > >     mutex_lock(&chip->lock);
> > > > -   chip->suspended = 1;
> > > > +   if (chip->_suspend)
> > > > +      if (!chip->_suspend(chip))
> > > > +         chip->suspended = 1;  
> > 
> > Shouldn't you propagate the error to the caller if chip->_suspend()
> > fails?  
> 
> Currently, chip->suspend() just do sending command to nand chip and
> I think caller could check chip->suspend = 1 or 0 to know the status
> of nand chip.

No, it can't. The caller (AKA the MTD layer) has no idea about this
chip->suspend field, actually it doesn't even know about the nand_chip
struct. The mtd->_suspend() hook is here to abstract HW details, so
it's the raw NAND framework responsibility to propagate the error code
returned by chip->suspend().