Re: [PATCH v2 19/26] media: ov9650: fix bogus warnings

[Nicholas Mc Guire]

On Thu, Nov 02, 2017 at 10:06:06AM +, Nicholas Mc Guire wrote:
> On Wed, Nov 01, 2017 at 05:05:56PM -0400, Mauro Carvalho Chehab wrote:
> > The smatch logic gets confused with the syntax used to check if the
> > ov9650x_read() reads succedded:
> > drivers/media/i2c/ov9650.c:895 __g_volatile_ctrl() error: uninitialized 
> > symbol 'reg2'.
> > drivers/media/i2c/ov9650.c:895 __g_volatile_ctrl() error: uninitialized 
> > symbol 'reg1'.
> > 
> > There's nothing wrong with the original logic, except that
> > it is a little more harder to review.
> 
> Maybe I do not understand the original logic correctly but
> ov965x_read(...) is passing on the return value from 
> i2c_transfer() -> __i2c_transfer() and thus if one of those
> calls would have been a negativ error status it would have simply
> executed the next call to ov965x_read() and if that 
> call would have suceeded it would eventually reach the
> line " exposure = ((reg2 & 0x3f) << 10) | (reg1 << 2) |..."
> with the potential to operate on uninitialized registers reg0/1/2
> the current code sems only to handle error conditions in the last
> call to ov965x_read() correctly.

sorry - sent that out too fast - the logic is equivalent the negative
returns are treated correctly because only the success case is 
being returned explicidly as 0 in ov965x_read() return statement
by checking for the expecte return of 1 from i2c_transfer() wrapping
it to 0.

sorry for the noise.

thx!
hofrat

> 
> I think this is actually not an equivalent transform but a bug-fix
> of  case V4L2_CID_EXPOSURE_AUTO: (aside from being a code inconsistency)
> So should this not carry a 
>  Fixes: 84a15ded76ec ("[media] V4L: Add driver for OV9650/52 image sensors")
> tag ?
> 
> thx!
> hofrat
> 
> > 
> > So, let's stick with the syntax that won't cause read
> > issues.
> > 
> > Signed-off-by: Mauro Carvalho Chehab 
> 
> Reviewed-by: Nicholas Mc Guire 
> 
> > ---
> >  drivers/media/i2c/ov9650.c | 10 ++
> >  1 file changed, 6 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/media/i2c/ov9650.c b/drivers/media/i2c/ov9650.c
> > index 69433e1e2533..e519f278d5f9 100644
> > --- a/drivers/media/i2c/ov9650.c
> > +++ b/drivers/media/i2c/ov9650.c
> > @@ -886,10 +886,12 @@ static int __g_volatile_ctrl(struct ov965x *ov965x, 
> > struct v4l2_ctrl *ctrl)
> > if (ctrl->val == V4L2_EXPOSURE_MANUAL)
> > return 0;
> > ret = ov965x_read(client, REG_COM1, );
> > -   if (!ret)
> > -   ret = ov965x_read(client, REG_AECH, );
> > -   if (!ret)
> > -   ret = ov965x_read(client, REG_AECHM, );
> > +   if (ret < 0)
> > +   return ret;
> > +   ret = ov965x_read(client, REG_AECH, );
> > +   if (ret < 0)
> > +   return ret;
> > +   ret = ov965x_read(client, REG_AECHM, );
> > if (ret < 0)
> > return ret;
> > exposure = ((reg2 & 0x3f) << 10) | (reg1 << 2) |
> > -- 
> > 2.13.6
> > 

Re: [PATCH v2 19/26] media: ov9650: fix bogus warnings

[Nicholas Mc Guire]

On Wed, Nov 01, 2017 at 05:05:56PM -0400, Mauro Carvalho Chehab wrote:
> The smatch logic gets confused with the syntax used to check if the
> ov9650x_read() reads succedded:
>   drivers/media/i2c/ov9650.c:895 __g_volatile_ctrl() error: uninitialized 
> symbol 'reg2'.
>   drivers/media/i2c/ov9650.c:895 __g_volatile_ctrl() error: uninitialized 
> symbol 'reg1'.
> 
> There's nothing wrong with the original logic, except that
> it is a little more harder to review.

Maybe I do not understand the original logic correctly but
ov965x_read(...) is passing on the return value from 
i2c_transfer() -> __i2c_transfer() and thus if one of those
calls would have been a negativ error status it would have simply
executed the next call to ov965x_read() and if that 
call would have suceeded it would eventually reach the
line " exposure = ((reg2 & 0x3f) << 10) | (reg1 << 2) |..."
with the potential to operate on uninitialized registers reg0/1/2
the current code sems only to handle error conditions in the last
call to ov965x_read() correctly.

I think this is actually not an equivalent transform but a bug-fix
of  case V4L2_CID_EXPOSURE_AUTO: (aside from being a code inconsistency)
So should this not carry a 
 Fixes: 84a15ded76ec ("[media] V4L: Add driver for OV9650/52 image sensors")
tag ?

thx!
hofrat

> 
> So, let's stick with the syntax that won't cause read
> issues.
> 
> Signed-off-by: Mauro Carvalho Chehab 

Reviewed-by: Nicholas Mc Guire 

> ---
>  drivers/media/i2c/ov9650.c | 10 ++
>  1 file changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/media/i2c/ov9650.c b/drivers/media/i2c/ov9650.c
> index 69433e1e2533..e519f278d5f9 100644
> --- a/drivers/media/i2c/ov9650.c
> +++ b/drivers/media/i2c/ov9650.c
> @@ -886,10 +886,12 @@ static int __g_volatile_ctrl(struct ov965x *ov965x, 
> struct v4l2_ctrl *ctrl)
>   if (ctrl->val == V4L2_EXPOSURE_MANUAL)
>   return 0;
>   ret = ov965x_read(client, REG_COM1, );
> - if (!ret)
> - ret = ov965x_read(client, REG_AECH, );
> - if (!ret)
> - ret = ov965x_read(client, REG_AECHM, );
> + if (ret < 0)
> + return ret;
> + ret = ov965x_read(client, REG_AECH, );
> + if (ret < 0)
> + return ret;
> + ret = ov965x_read(client, REG_AECHM, );
>   if (ret < 0)
>   return ret;
>   exposure = ((reg2 & 0x3f) << 10) | (reg1 << 2) |
> -- 
> 2.13.6
> 

[PATCH v2 19/26] media: ov9650: fix bogus warnings

[Mauro Carvalho Chehab]

The smatch logic gets confused with the syntax used to check if the
ov9650x_read() reads succedded:
drivers/media/i2c/ov9650.c:895 __g_volatile_ctrl() error: uninitialized 
symbol 'reg2'.
drivers/media/i2c/ov9650.c:895 __g_volatile_ctrl() error: uninitialized 
symbol 'reg1'.

There's nothing wrong with the original logic, except that
it is a little more harder to review.

So, let's stick with the syntax that won't cause read
issues.

Signed-off-by: Mauro Carvalho Chehab 
---
 drivers/media/i2c/ov9650.c | 10 ++
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/drivers/media/i2c/ov9650.c b/drivers/media/i2c/ov9650.c
index 69433e1e2533..e519f278d5f9 100644
--- a/drivers/media/i2c/ov9650.c
+++ b/drivers/media/i2c/ov9650.c
@@ -886,10 +886,12 @@ static int __g_volatile_ctrl(struct ov965x *ov965x, 
struct v4l2_ctrl *ctrl)
if (ctrl->val == V4L2_EXPOSURE_MANUAL)
return 0;
ret = ov965x_read(client, REG_COM1, );
-   if (!ret)
-   ret = ov965x_read(client, REG_AECH, );
-   if (!ret)
-   ret = ov965x_read(client, REG_AECHM, );
+   if (ret < 0)
+   return ret;
+   ret = ov965x_read(client, REG_AECH, );
+   if (ret < 0)
+   return ret;
+   ret = ov965x_read(client, REG_AECHM, );
if (ret < 0)
return ret;
exposure = ((reg2 & 0x3f) << 10) | (reg1 << 2) |
-- 
2.13.6