[PATCH] mtdchar: handle chips that have user otp but no factory otp

[Uwe Kleine-König]

Hello,

On Sat, Mar 02, 2013 at 05:41:24PM +0200, Artem Bityutskiy wrote:
> On Mon, 2013-02-18 at 11:19 +0100, Uwe Kleine-König wrote:
> > Before this patch mtd_read_fact_prot_reg was used to check availability
> > for both MTD_OTP_FACTORY and MTD_OTP_USER access. This made accessing
> > user otp for chips that don't have a factory otp area impossible. So use
> > the right wrapper depending on the intended area to be accessed.
> > 
> > Signed-off-by: Uwe Kleine-König <u.kleine-koenig at pengutronix.de>
> > ---
> > Hello,
> > 
> > I'm currently working on accessing the user otp area of MT29F2G nand
> > flash that doesn't have a factory otp. Reading and writing are not ready
> > yet, but this change is an obvious prerequisite.
> > 
> > Best regards
> > Uwe
> > 
> >  drivers/mtd/mtdchar.c |   30 +++++++++++++++++++-----------
> >  1 file changed, 19 insertions(+), 11 deletions(-)
> > 
> > diff --git a/drivers/mtd/mtdchar.c b/drivers/mtd/mtdchar.c
> > index a6e7451..1f4034a 100644
> > --- a/drivers/mtd/mtdchar.c
> > +++ b/drivers/mtd/mtdchar.c
> > @@ -371,26 +371,34 @@ static int otp_select_filemode(struct mtd_file_info *mfi, int mode)
> >  	struct mtd_info *mtd = mfi->mtd;
> >  	size_t retlen;
> >  	int ret = 0;
> > -
> > -	/*
> > -	 * Make a fake call to mtd_read_fact_prot_reg() to check if OTP
> > -	 * operations are supported.
> > -	 */
> > -	if (mtd_read_fact_prot_reg(mtd, -1, 0, &retlen, NULL) == -EOPNOTSUPP)
> > -		return -EOPNOTSUPP;
> > +	int (*func)(struct mtd_info *, loff_t, size_t, size_t *, u_char *) =
> > +		NULL;
> > +	enum mtd_file_modes outmode = MTD_FILE_MODE_NORMAL;
> 
> In this particular case when we only have 2 modes I'd prefer to not
> introduce a function pointer variable but directly call the function.
I choosed the function pointer to reduce code duplication. Do function
pointer have a bad characteristic that I don't know? But actually I
don't care much and can resend without the function pointer.
> >  
> >  	switch (mode) {
> >  	case MTD_OTP_FACTORY:
> > -		mfi->mode = MTD_FILE_MODE_OTP_FACTORY;
> > +		outmode = MTD_FILE_MODE_OTP_FACTORY;
> > +		func = mtd_read_fact_prot_reg;
> >  		break;
> >  	case MTD_OTP_USER:
> > -		mfi->mode = MTD_FILE_MODE_OTP_USER;
> > +		outmode = MTD_FILE_MODE_OTP_USER;
> > +		func = mtd_read_user_prot_reg;
> >  		break;
> > -	default:
> > -		ret = -EINVAL;
> >  	case MTD_OTP_OFF:
> >  		break;
> > +	default:
> > +		ret = -EINVAL;
> 
> Probably in this case you need to 'return -EINVAL', otherwise you modify
> 'mfi->mode' below which is an unexpected side-effect of '-EINVAL'.
I don't remember, but I think I convinced myself that it doesn't hurt.
Still it's less surprising to not modify mfi, so OK.

Uwe

> >  	}
> > +
> > +	/*
> > +	 * Make a fake call to mtd_read_fact_prot_reg() or
> > +	 * mtd_read_user_prot_reg() to check if OTP operations are supported.
> > +	 */
> > +	if (func && func(mtd, -1, 0, &retlen, NULL) == -EOPNOTSUPP)
> > +		return -EOPNOTSUPP;
> > +
> > +	mfi->mode = outmode;
> > +
> >  	return ret;
> >  }
> >  #else
> 
> -- 
> Best Regards,
> Artem Bityutskiy
> 
> 

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
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