[PATCH] staging: gpib: Remove a dead condition in if statement

[PATCH] staging: gpib: Remove a dead condition in if statement

[Everest K.C.]

The variable `residue` is an unsigned int, also the function
`fluke_get_dma_residue` returns an unsigned int. The value of
an unsigned int can only be 0 at minimum.
The less-than-zero comparision can never be true.
Fix it by removing the dead condition in the if statement.

This issue was reported by Coverity Scan.
Report:
CID 1600782: (#1 of 1): Macro compares unsigned to 0 (NO_EFFECT)
unsigned_compare: This less-than-zero comparison of an unsigned value
is never true. residue < 0U.

Fixes: 55936779f496 ("staging: gpib: Add Fluke cda based cards GPIB driver")
Signed-off-by: Everest K.C. <everestkc@everestkc.com.np>
---
 drivers/staging/gpib/eastwood/fluke_gpib.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/staging/gpib/eastwood/fluke_gpib.c b/drivers/staging/gpib/eastwood/fluke_gpib.c
index f9f149db222d..51b4f9891a34 100644
--- a/drivers/staging/gpib/eastwood/fluke_gpib.c
+++ b/drivers/staging/gpib/eastwood/fluke_gpib.c
@@ -644,7 +644,7 @@ static int fluke_dma_read(gpib_board_t *board, uint8_t *buffer,
 	 */
 	usleep_range(10, 15);
 	residue = fluke_get_dma_residue(e_priv->dma_channel, dma_cookie);
-	if (WARN_ON_ONCE(residue > length || residue < 0))
+	if (WARN_ON_ONCE(residue > length))
 		return -EFAULT;
 	*bytes_read += length - residue;
 	dmaengine_terminate_all(e_priv->dma_channel);
-- 
2.43.0

Re: [PATCH] staging: gpib: Remove a dead condition in if statement

[Shuah Khan]

On 10/15/24 14:06, Everest K.C. wrote:
> The variable `residue` is an unsigned int, also the function
> `fluke_get_dma_residue` returns an unsigned int. The value of
> an unsigned int can only be 0 at minimum.
> The less-than-zero comparision can never be true.
> Fix it by removing the dead condition in the if statement.
> 
> This issue was reported by Coverity Scan.
> Report:
> CID 1600782: (#1 of 1): Macro compares unsigned to 0 (NO_EFFECT)
> unsigned_compare: This less-than-zero comparison of an unsigned value
> is never true. residue < 0U.
> 
> Fixes: 55936779f496 ("staging: gpib: Add Fluke cda based cards GPIB driver")
> Signed-off-by: Everest K.C. <everestkc@everestkc.com.np>
> ---
>   drivers/staging/gpib/eastwood/fluke_gpib.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/staging/gpib/eastwood/fluke_gpib.c b/drivers/staging/gpib/eastwood/fluke_gpib.c
> index f9f149db222d..51b4f9891a34 100644
> --- a/drivers/staging/gpib/eastwood/fluke_gpib.c
> +++ b/drivers/staging/gpib/eastwood/fluke_gpib.c
> @@ -644,7 +644,7 @@ static int fluke_dma_read(gpib_board_t *board, uint8_t *buffer,
>   	 */
>   	usleep_range(10, 15);
>   	residue = fluke_get_dma_residue(e_priv->dma_channel, dma_cookie);
> -	if (WARN_ON_ONCE(residue > length || residue < 0))
> +	if (WARN_ON_ONCE(residue > length))

Are you sure this is the right fix? length is size_t
fluke_get_dma_residue() returns unsigned int - yes
the coverity report is correct, but should fluke_get_dma_residue()
return size_t?

>   		return -EFAULT;
>   	*bytes_read += length - residue;

bytes_read is also size_t

>   	dmaengine_terminate_all(e_priv->dma_channel);

The patch should indicate it is against next. [PATCH next].

thanks,
-- Shuah

Re: [PATCH] staging: gpib: Remove a dead condition in if statement

[Everest K.C.]

On Tue, Oct 15, 2024 at 4:47 PM Shuah Khan <skhan@linuxfoundation.org> wrote:
>
> On 10/15/24 14:06, Everest K.C. wrote:
> > The variable `residue` is an unsigned int, also the function
> > `fluke_get_dma_residue` returns an unsigned int. The value of
> > an unsigned int can only be 0 at minimum.
> > The less-than-zero comparision can never be true.
> > Fix it by removing the dead condition in the if statement.
> >
> > This issue was reported by Coverity Scan.
> > Report:
> > CID 1600782: (#1 of 1): Macro compares unsigned to 0 (NO_EFFECT)
> > unsigned_compare: This less-than-zero comparison of an unsigned value
> > is never true. residue < 0U.
> >
> > Fixes: 55936779f496 ("staging: gpib: Add Fluke cda based cards GPIB driver")
> > Signed-off-by: Everest K.C. <everestkc@everestkc.com.np>
> > ---
> >   drivers/staging/gpib/eastwood/fluke_gpib.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/staging/gpib/eastwood/fluke_gpib.c b/drivers/staging/gpib/eastwood/fluke_gpib.c
> > index f9f149db222d..51b4f9891a34 100644
> > --- a/drivers/staging/gpib/eastwood/fluke_gpib.c
> > +++ b/drivers/staging/gpib/eastwood/fluke_gpib.c
> > @@ -644,7 +644,7 @@ static int fluke_dma_read(gpib_board_t *board, uint8_t *buffer,
> >        */
> >       usleep_range(10, 15);
> >       residue = fluke_get_dma_residue(e_priv->dma_channel, dma_cookie);
> > -     if (WARN_ON_ONCE(residue > length || residue < 0))
> > +     if (WARN_ON_ONCE(residue > length))
>
> Are you sure this is the right fix? length is size_t
> fluke_get_dma_residue() returns unsigned int - yes
> the coverity report is correct, but should fluke_get_dma_residue()
> return size_t?
I agree that it looks kind of inconsistent. The variable residue returned
by fluke_get_dma_residue() is defined in a u32 defined in struct dma_tx_state.
I will wait for the feedback from the maintainers on this.
> >               return -EFAULT;
> >       *bytes_read += length - residue;
>
> bytes_read is also size_t
>
> >       dmaengine_terminate_all(e_priv->dma_channel);
>
> The patch should indicate it is against next. [PATCH next].
The patch was created from linux staging.
> thanks,
> -- Shuah
>
>
Thanks,
Everest K.C.

Re: [PATCH] staging: gpib: Remove a dead condition in if statement

[Greg KH]

On Tue, Oct 15, 2024 at 02:06:47PM -0600, Everest K.C. wrote:
> The variable `residue` is an unsigned int, also the function
> `fluke_get_dma_residue` returns an unsigned int. The value of
> an unsigned int can only be 0 at minimum.
> The less-than-zero comparision can never be true.
> Fix it by removing the dead condition in the if statement.
> 
> This issue was reported by Coverity Scan.
> Report:
> CID 1600782: (#1 of 1): Macro compares unsigned to 0 (NO_EFFECT)
> unsigned_compare: This less-than-zero comparison of an unsigned value
> is never true. residue < 0U.
> 
> Fixes: 55936779f496 ("staging: gpib: Add Fluke cda based cards GPIB driver")

Again, a code cleanup does not deserve a "Fixes:" tag, sorry.

thanks,

greg k-h