Re: [RESEND v5 07/21] mtd: rawnand: Create a new enumeration to describe OOB placement

[Miquel Raynal <miquel.raynal@xxxxxxxxxxx>]

Hi Boris,

Boris Brezillon <boris.brezillon@xxxxxxxxxxxxx> wrote on Wed, 27 May
2020 00:39:04 +0200:

> On Tue, 26 May 2020 21:56:19 +0200
> Miquel Raynal <miquel.raynal@xxxxxxxxxxx> wrote:
> 
> > There is currently a confusion between the ECC type/mode/provider
> > (eg. hardware, software, on-die or none) and the ECC bytes placement.
> > 
> > Create a new enumeration to describe this placement.
> > 
> > Signed-off-by: Miquel Raynal <miquel.raynal@xxxxxxxxxxx>
> > Reviewed-by: Boris Brezillon <boris.brezillon@xxxxxxxxxxxxx>
> > ---
> >  drivers/mtd/nand/raw/nand_base.c |  4 ++++
> >  include/linux/mtd/rawnand.h      | 12 ++++++++++++
> >  2 files changed, 16 insertions(+)
> > 
> > diff --git a/drivers/mtd/nand/raw/nand_base.c b/drivers/mtd/nand/raw/nand_base.c
> > index ef70ca0828c3..a4470a19c805 100644
> > --- a/drivers/mtd/nand/raw/nand_base.c
> > +++ b/drivers/mtd/nand/raw/nand_base.c
> > @@ -5018,6 +5018,10 @@ static const char * const nand_ecc_modes[] = {
> >  	[NAND_ECC_ON_DIE]	= "on-die",
> >  };
> >  
> > +static const char * const nand_ecc_placement[] = {
> > +	[NAND_ECC_PLACEMENT_INTERLEAVED] = "interleaved",
> > +};
> > +
> >  static int of_get_nand_ecc_mode(struct device_node *np)
> >  {
> >  	const char *pm;
> > diff --git a/include/linux/mtd/rawnand.h b/include/linux/mtd/rawnand.h
> > index 8187056dd3a0..6eb4d91b07eb 100644
> > --- a/include/linux/mtd/rawnand.h
> > +++ b/include/linux/mtd/rawnand.h
> > @@ -92,6 +92,18 @@ enum nand_ecc_mode {
> >  	NAND_ECC_ON_DIE,
> >  };
> >  
> > +/**
> > + * enum nand_ecc_placement - NAND ECC placement
> > + * @NAND_ECC_PLACEMENT_FREE: The driver can decide where to put ECC bytes.  
> 
> Can we name that one UNDEFINED instead of FREE, and it's not really the
> driver that decides (unless you have a choice or use SW ECC), more the ECC
> engine itself.

Ack.

> 
> > + *                           Default behavior is to put them at the end of the
> > + *                           OOB area.  
> 
> I wouldn't even define a default behavior here, but instead add a value for
> OOB/TAIL placement.

This is for legacy reasons, maybe I should not say it is a default, but
rather a common location (or say nothing).

> 
> > + * @NAND_ECC_PLACEMENT_INTERLEAVED: Syndrome layout: interleave data and OOB.  
> 
> 
> 									     ^ECC bytes
> 
> > + */
> > +enum nand_ecc_placement {
> > +	NAND_ECC_PLACEMENT_FREE,
> > +	NAND_ECC_PLACEMENT_INTERLEAVED,
> > +};
> > +
> >  enum nand_ecc_algo {
> >  	NAND_ECC_UNKNOWN,
> >  	NAND_ECC_HAMMING,  
> 

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