Re: [PATCH 1/2] mtd: nand: Drop mtd.owner requirement in nand_scan

[Boris Brezillon <boris.brezillon@free-electrons.com>]

On Fri, 1 Apr 2016 15:26:49 -0700
Brian Norris <computersforpeace@gmail.com> wrote:

> On Fri, Apr 01, 2016 at 06:29:23PM -0300, Ezequiel Garcia wrote:
> > Since commit 807f16d4db95 ("mtd: core: set some defaults
> > when dev.parent is set"), it's now legal for drivers
> > to call nand_scan and nand_scan_ident without setting
> > mtd.owner.
> > 
> > Drop the check and while at it remove the BUG() abuse.
> > 
> > Signed-off-by: Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>

Acked-by: Boris Brezillon <boris.brezillon@free-electrons.com>

> > ---
> >  drivers/mtd/nand/nand_base.c | 10 +---------
> >  1 file changed, 1 insertion(+), 9 deletions(-)
> > 
> > diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
> > index c3733a10a6e7..befa04ef4a04 100644
> > --- a/drivers/mtd/nand/nand_base.c
> > +++ b/drivers/mtd/nand/nand_base.c
> > @@ -4013,7 +4013,6 @@ static int nand_dt_init(struct nand_chip *chip)
> >   * This is the first phase of the normal nand_scan() function. It reads the
> >   * flash ID and sets up MTD fields accordingly.
> >   *
> > - * The mtd->owner field must be set to the module of the caller.
> >   */
> >  int nand_scan_ident(struct mtd_info *mtd, int maxchips,
> >  		    struct nand_flash_dev *table)
> > @@ -4433,19 +4432,12 @@ EXPORT_SYMBOL(nand_scan_tail);
> >   *
> >   * This fills out all the uninitialized function pointers with the defaults.
> >   * The flash ID is read and the mtd/chip structures are filled with the
> > - * appropriate values. The mtd->owner field must be set to the module of the
> > - * caller.
> > + * appropriate values.
> >   */
> >  int nand_scan(struct mtd_info *mtd, int maxchips)
> >  {
> >  	int ret;
> >  
> > -	/* Many callers got this wrong, so check for it for a while... */
> > -	if (!mtd->owner && caller_is_module()) {
> > -		pr_crit("%s called with NULL mtd->owner!\n", __func__);
> > -		BUG();
> > -	}
> 
> Ooh, yikes! Forgot this was there. I guess no one noticed, because fewer
> drivers are using plain nand_scan() these days (instead of splitting up
> nand_scan_ident() and nand_scan_tail()), and also, many NAND users don't
> run their drivers as modules.
> 
> Anyway, this is probably worth -stable, right? (i.e., "Fixes:
> 807f16d4db95 ..." and "Cc: <stable@vger.kernel.org>")
> 
> I can take this directly, or Boris, if you feel like there will be other
> for-v4.5 NAND material, you can queue this up instead.

No, take it directly.

On a more general note, not sure creating a nand/fixes branch and
sending you PRs after each -rc (if fixes are available of course) is
really efficient. Maybe I'm wrong, but I don't expect to see more than a
couple of fixes per release, and it's probably better if you keep
taking them directly (with my acks).

What do you think?


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