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 ‘onenand_check_features’:
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 <[email protected]>
Signed-off-by: Gustavo A. R. Silva <[email protected]>
---
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 - ? */
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 - ? */
case ONENAND_DEVICE_DENSITY_1Gb:
/* A-Die has all block unlock */
--
2.21.0
Sorry for being late to speaking up on this. I missed something in the
code the first time I read the thread, that now stood out to me. Notes
below...
On Wed, May 22, 2019 at 01:04:46PM -0500, Gustavo A. R. Silva wrote:
> 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)
Reverse-order review, second hunk first:
> 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 - ? */
>
> case ONENAND_DEVICE_DENSITY_1Gb:
> /* A-Die has all block unlock */
So, I think the ONENAND_DEVICE_DENSITY_2Gb should be a "break". Though,
actually, it doesn't matter:
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;
case ONENAND_DEVICE_DENSITY_1Gb:
/* A-Die has all block unlock */
if (process)
this->options |= ONENAND_HAS_UNLOCK_ALL;
break;
Falling through from ONENAND_DEVICE_DENSITY_2Gb to
ONENAND_DEVICE_DENSITY_1Gb will actually have no side-effects:
ONENAND_HAS_UNLOCK_ALL was unconditionally set in ..._2Gb, so there is
no reason to fall through to ..._1Gb. (But falling through is harmless.)
Now the first hunk:
> if ((this->version_id & 0xf) == 0xe)
> this->options |= ONENAND_HAS_NOP_1;
> }
> + /* Fall through - ? */
>
case ONENAND_DEVICE_DENSITY_4Gb:
if (ONENAND_IS_DDP(this))
this->options |= ONENAND_HAS_2PLANE;
else if (numbufs == 1) {
this->options |= ONENAND_HAS_4KB_PAGE;
this->options |= ONENAND_HAS_CACHE_PROGRAM;
/*
* There are two different 4KiB pagesize chips
* and no way to detect it by H/W config values.
*
* To detect the correct NOP for each chips,
* It should check the version ID as workaround.
*
* Now it has as following
* KFM4G16Q4M has NOP 4 with version ID 0x0131
* KFM4G16Q5M has NOP 1 with versoin ID 0x013e
*/
if ((this->version_id & 0xf) == 0xe)
this->options |= ONENAND_HAS_NOP_1;
}
Falling through from ONENAND_DEVICE_DENSITY_4Gb to
ONENAND_DEVICE_DENSITY_2Gb looks like it would mean that
ONENAND_HAS_2PLANE would be unconditionally set for ...4Gb, which seems
very strange to expect:
if (ONENAND_IS_DDP(this))
this->options |= ONENAND_HAS_2PLANE;
...
if (!ONENAND_IS_DDP(this))
this->options |= ONENAND_HAS_2PLANE;
However! This happens later:
if (ONENAND_IS_4KB_PAGE(this))
this->options &= ~ONENAND_HAS_2PLANE;
i.e. falling through to ...2Gb (which sets ONENAND_HAS_2PLANE) has no
effect because when ONENAND_HAS_2PLANE isn't set (numbufs == 1), it gets
_cleared_ by the above code due to ONENAND_HAS_4KB_PAGE getting set:
#define ONENAND_IS_4KB_PAGE(this) \
(this->options & ONENAND_HAS_4KB_PAGE)
Unfortunately, though, it's less clear about ONENAND_HAS_UNLOCK_ALL,
which is getting set unconditionally for ...4Gb currently (due to the
fallthrough to ...2Gb). However, this happens later:
if (FLEXONENAND(this)) {
this->options &= ~ONENAND_HAS_CONT_LOCK;
this->options |= ONENAND_HAS_UNLOCK_ALL;
}
...
#define FLEXONENAND(this) \
(this->device_id & DEVICE_IS_FLEXONENAND)
So it's possible this fall through has no effect (are all 4Gb density
devices also FLEXONENAND devices?)
Setting a "break" after 4Gb may remove ONENAND_HAS_UNLOCK_ALL in the
!FLEXONENAND(this) case. Does anyone have real hardware to test with?
Thoughts?
--
Kees Cook
On Wed, 22 May 2019 13:04:46 -0500
"Gustavo A. R. Silva" <[email protected]> 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 ‘onenand_check_features’:
> 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 <[email protected]>
> Signed-off-by: Gustavo A. R. Silva <[email protected]>
> ---
> 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 */
On Wed, May 22, 2019 at 11:37:05PM +0200, Boris Brezillon wrote:
> > @@ -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 */
>
Your reply was much more to-the-point than mine. :) I'd agree: retain
existing behavior (ONENAND_HAS_UNLOCK_ALL) and add breaks.
--
Kees Cook
On Wed, 22 May 2019 14:30:11 -0700
Kees Cook <[email protected]> wrote:
> Sorry for being late to speaking up on this. I missed something in the
> code the first time I read the thread, that now stood out to me. Notes
> below...
>
> On Wed, May 22, 2019 at 01:04:46PM -0500, Gustavo A. R. Silva wrote:
> > 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)
>
> Reverse-order review, second hunk first:
>
> > 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 - ? */
> >
> > case ONENAND_DEVICE_DENSITY_1Gb:
> > /* A-Die has all block unlock */
>
> So, I think the ONENAND_DEVICE_DENSITY_2Gb should be a "break". Though,
> actually, it doesn't matter:
>
> 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;
>
> case ONENAND_DEVICE_DENSITY_1Gb:
> /* A-Die has all block unlock */
> if (process)
> this->options |= ONENAND_HAS_UNLOCK_ALL;
> break;
>
> Falling through from ONENAND_DEVICE_DENSITY_2Gb to
> ONENAND_DEVICE_DENSITY_1Gb will actually have no side-effects:
> ONENAND_HAS_UNLOCK_ALL was unconditionally set in ..._2Gb, so there is
> no reason to fall through to ..._1Gb. (But falling through is harmless.)
>
> Now the first hunk:
>
> > if ((this->version_id & 0xf) == 0xe)
> > this->options |= ONENAND_HAS_NOP_1;
> > }
> > + /* Fall through - ? */
> >
>
> case ONENAND_DEVICE_DENSITY_4Gb:
> if (ONENAND_IS_DDP(this))
> this->options |= ONENAND_HAS_2PLANE;
> else if (numbufs == 1) {
> this->options |= ONENAND_HAS_4KB_PAGE;
> this->options |= ONENAND_HAS_CACHE_PROGRAM;
> /*
> * There are two different 4KiB pagesize chips
> * and no way to detect it by H/W config values.
> *
> * To detect the correct NOP for each chips,
> * It should check the version ID as workaround.
> *
> * Now it has as following
> * KFM4G16Q4M has NOP 4 with version ID 0x0131
> * KFM4G16Q5M has NOP 1 with versoin ID 0x013e
> */
> if ((this->version_id & 0xf) == 0xe)
> this->options |= ONENAND_HAS_NOP_1;
> }
>
> Falling through from ONENAND_DEVICE_DENSITY_4Gb to
> ONENAND_DEVICE_DENSITY_2Gb looks like it would mean that
> ONENAND_HAS_2PLANE would be unconditionally set for ...4Gb, which seems
> very strange to expect:
>
> if (ONENAND_IS_DDP(this))
> this->options |= ONENAND_HAS_2PLANE;
> ...
> if (!ONENAND_IS_DDP(this))
> this->options |= ONENAND_HAS_2PLANE;
Oops, didn't notice the ! on the second test.
>
> However! This happens later:
>
> if (ONENAND_IS_4KB_PAGE(this))
> this->options &= ~ONENAND_HAS_2PLANE;
>
> i.e. falling through to ...2Gb (which sets ONENAND_HAS_2PLANE) has no
> effect because when ONENAND_HAS_2PLANE isn't set (numbufs == 1), it gets
> _cleared_ by the above code due to ONENAND_HAS_4KB_PAGE getting set:
Are you sure !DDP implies num_bufs == 1?
>
> #define ONENAND_IS_4KB_PAGE(this) \
> (this->options & ONENAND_HAS_4KB_PAGE)
>
>
> Unfortunately, though, it's less clear about ONENAND_HAS_UNLOCK_ALL,
> which is getting set unconditionally for ...4Gb currently (due to the
> fallthrough to ...2Gb). However, this happens later:
>
> if (FLEXONENAND(this)) {
> this->options &= ~ONENAND_HAS_CONT_LOCK;
> this->options |= ONENAND_HAS_UNLOCK_ALL;
> }
> ...
> #define FLEXONENAND(this) \
> (this->device_id & DEVICE_IS_FLEXONENAND)
>
> So it's possible this fall through has no effect (are all 4Gb density
> devices also FLEXONENAND devices?)
>
All this look suspicious, and even if the fall through logic
has no side effects in practice (which I'm still not sure is the case),
I think it'd be better to explicitly set the flags that have
to be set in each case statement and add breaks.
On Wed, May 22, 2019 at 11:57:38PM +0200, Boris Brezillon wrote:
> All this look suspicious, and even if the fall through logic
> has no side effects in practice (which I'm still not sure is the case),
> I think it'd be better to explicitly set the flags that have
> to be set in each case statement and add breaks.
Yeah, totally agreed. :)
--
Kees Cook
On 5/22/19 5:20 PM, Kees Cook wrote:
> On Wed, May 22, 2019 at 11:57:38PM +0200, Boris Brezillon wrote:
>> All this look suspicious, and even if the fall through logic
>> has no side effects in practice (which I'm still not sure is the case),
>> I think it'd be better to explicitly set the flags that have
>> to be set in each case statement and add breaks.
>
> Yeah, totally agreed. :)
>
Thank you, Kees and Boris for the feedback. Some external opinions were
certainly much needed here.
I'll just wait for any comments from the MTD guys.
Thanks
--
Gustavo