Re: [PATCH] mtd: onenand_base: Avoid fall-through warnings
From: Boris Brezillon
Date: Wed May 22 2019 - 17:39:57 EST
On Wed, 22 May 2019 13:04:46 -0500
"Gustavo A. R. Silva" <gustavo@xxxxxxxxxxxxxx> wrote:
> NOTICE THAT:
>
> "...we don't know whether we need fallthroughs or breaks there and this
> is just a change to avoid having new warnings when switching to
> -Wimplicit-fallthrough but this change might be entirely wrong."[1]
>
> See the original thread of discussion here:
>
> https://lore.kernel.org/patchwork/patch/1036251/
>
> So, in preparation to enabling -Wimplicit-fallthrough, this patch silences
> the following warnings:
>
> drivers/mtd/nand/onenand/onenand_base.c: In function âonenand_check_featuresâ:
> drivers/mtd/nand/onenand/onenand_base.c:3264:6: warning: this statement may fall through [-Wimplicit-fallthrough=]
> if (ONENAND_IS_DDP(this))
> ^
> drivers/mtd/nand/onenand/onenand_base.c:3284:2: note: here
> case ONENAND_DEVICE_DENSITY_2Gb:
> ^~~~
> drivers/mtd/nand/onenand/onenand_base.c:3288:17: warning: this statement may fall through [-Wimplicit-fallthrough=]
> this->options |= ONENAND_HAS_UNLOCK_ALL;
> drivers/mtd/nand/onenand/onenand_base.c:3290:2: note: here
> case ONENAND_DEVICE_DENSITY_1Gb:
> ^~~~
>
> Warning level 3 was used: -Wimplicit-fallthrough=3
>
> This patch is part of the ongoing efforts to enable
> -Wimplicit-fallthrough.
>
> [1] https://lore.kernel.org/lkml/20190509085318.34a9d4be@xps13/
>
> Cc: Miquel Raynal <miquel.raynal@xxxxxxxxxxx>
> Signed-off-by: Gustavo A. R. Silva <gustavo@xxxxxxxxxxxxxx>
> ---
> drivers/mtd/nand/onenand/onenand_base.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/drivers/mtd/nand/onenand/onenand_base.c b/drivers/mtd/nand/onenand/onenand_base.c
> index f41d76248550..6cf4df9f8c01 100644
> --- a/drivers/mtd/nand/onenand/onenand_base.c
> +++ b/drivers/mtd/nand/onenand/onenand_base.c
> @@ -3280,12 +3280,14 @@ static void onenand_check_features(struct mtd_info *mtd)
> if ((this->version_id & 0xf) == 0xe)
> this->options |= ONENAND_HAS_NOP_1;
> }
> + /* Fall through - ? */
So, the only thing that you'll re-use by falling through the next case
is the '->options |= ONENAND_HAS_UNLOCK_ALL' operation. I find it easier
to follow with an explicit copy of this line + a break.
>
> case ONENAND_DEVICE_DENSITY_2Gb:
> /* 2Gb DDP does not have 2 plane */
> if (!ONENAND_IS_DDP(this))
> this->options |= ONENAND_HAS_2PLANE;
> this->options |= ONENAND_HAS_UNLOCK_ALL;
> + /* Fall through - ? */
This fall through certainly doesn't make sense, as the only thing that
might be done in the 1Gb case is conditionally adding the
HAS_UNLOCK_ALL flag, and this flag is already unconditionally set.
Please add a break here.
>
> case ONENAND_DEVICE_DENSITY_1Gb:
> /* A-Die has all block unlock */