[RESEND] drm/stm: fix warning about multiplication in condition

Message ID 20170906131331.2691300-1-arnd@arndb.de
State Accepted
Commit 3ff558e78bc517f10a1b087989f3fda87038b48c
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Series
  • [RESEND] drm/stm: fix warning about multiplication in condition
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Commit Message

Arnd Bergmann Sept. 6, 2017, 1:13 p.m.
gcc-7 complains about multiplying within a condition being
suspicious:

drivers/gpu/drm/stm/dw_mipi_dsi-stm.c: In function 'dsi_pll_get_clkout_khz':
drivers/gpu/drm/stm/dw_mipi_dsi-stm.c:117:10: error: '*' in boolean context, suggest '&&' instead [-Werror=int-in-bool-context]

The code here is correct, but can be easily rephrased to make
that more obvious. I also swap out the error handling and the normal
code path for clarity.

Fixes: b0f09a3c69d9 ("drm/stm: Add STM32 DSI controller driver")
Acked-by: Philippe Cornu <philippe.cornu@st.com>

Tested-by: Philippe Cornu <philippe.cornu@st.com>

Signed-off-by: Arnd Bergmann <arnd@arndb.de>

---
Originally sent on July 25, but never made it into linux-next.
The warning is currently disabled in mainline, but this seems
to be a legitimate instance, and we may want to turn it back
on in the future.
---
 drivers/gpu/drm/stm/dw_mipi_dsi-stm.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

-- 
2.9.0

Comments

Archit Taneja Sept. 7, 2017, 5:29 a.m. | #1
Hi Benjamin,

This should be pushed to drm-misc by you, right?

Thanks,
Archit

On 09/06/2017 06:43 PM, Arnd Bergmann wrote:
> gcc-7 complains about multiplying within a condition being

> suspicious:

> 

> drivers/gpu/drm/stm/dw_mipi_dsi-stm.c: In function 'dsi_pll_get_clkout_khz':

> drivers/gpu/drm/stm/dw_mipi_dsi-stm.c:117:10: error: '*' in boolean context, suggest '&&' instead [-Werror=int-in-bool-context]

> 

> The code here is correct, but can be easily rephrased to make

> that more obvious. I also swap out the error handling and the normal

> code path for clarity.

> 

> Fixes: b0f09a3c69d9 ("drm/stm: Add STM32 DSI controller driver")

> Acked-by: Philippe Cornu <philippe.cornu@st.com>

> Tested-by: Philippe Cornu <philippe.cornu@st.com>

> Signed-off-by: Arnd Bergmann <arnd@arndb.de>

> ---

> Originally sent on July 25, but never made it into linux-next.

> The warning is currently disabled in mainline, but this seems

> to be a legitimate instance, and we may want to turn it back

> on in the future.

> ---

>   drivers/gpu/drm/stm/dw_mipi_dsi-stm.c | 8 +++++---

>   1 file changed, 5 insertions(+), 3 deletions(-)

> 

> diff --git a/drivers/gpu/drm/stm/dw_mipi_dsi-stm.c b/drivers/gpu/drm/stm/dw_mipi_dsi-stm.c

> index 568c5d0461ea..e5b6310240fe 100644

> --- a/drivers/gpu/drm/stm/dw_mipi_dsi-stm.c

> +++ b/drivers/gpu/drm/stm/dw_mipi_dsi-stm.c

> @@ -113,11 +113,13 @@ static enum dsi_color dsi_color_from_mipi(enum mipi_dsi_pixel_format fmt)

>   

>   static int dsi_pll_get_clkout_khz(int clkin_khz, int idf, int ndiv, int odf)

>   {

> +	int divisor = idf * odf;

> +

>   	/* prevent from division by 0 */

> -	if (idf * odf)

> -		return DIV_ROUND_CLOSEST(clkin_khz * ndiv, idf * odf);

> +	if (!divisor)

> +		return 0;

>   

> -	return 0;

> +	return DIV_ROUND_CLOSEST(clkin_khz * ndiv, divisor);

>   }

>   

>   static int dsi_pll_get_params(int clkin_khz, int clkout_khz,

> 


-- 
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
a Linux Foundation Collaborative Project
Daniel Vetter Sept. 8, 2017, 6:30 a.m. | #2
On Thu, Sep 07, 2017 at 10:59:49AM +0530, Archit Taneja wrote:
> Hi Benjamin,

> 

> This should be pushed to drm-misc by you, right?


I applied it. I guess Philippe Cornu should also become drm-misc committer
instead of just acking a patch and hoping fairies will pick it up.
-Daniel

> 

> Thanks,

> Archit

> 

> On 09/06/2017 06:43 PM, Arnd Bergmann wrote:

> > gcc-7 complains about multiplying within a condition being

> > suspicious:

> > 

> > drivers/gpu/drm/stm/dw_mipi_dsi-stm.c: In function 'dsi_pll_get_clkout_khz':

> > drivers/gpu/drm/stm/dw_mipi_dsi-stm.c:117:10: error: '*' in boolean context, suggest '&&' instead [-Werror=int-in-bool-context]

> > 

> > The code here is correct, but can be easily rephrased to make

> > that more obvious. I also swap out the error handling and the normal

> > code path for clarity.

> > 

> > Fixes: b0f09a3c69d9 ("drm/stm: Add STM32 DSI controller driver")

> > Acked-by: Philippe Cornu <philippe.cornu@st.com>

> > Tested-by: Philippe Cornu <philippe.cornu@st.com>

> > Signed-off-by: Arnd Bergmann <arnd@arndb.de>

> > ---

> > Originally sent on July 25, but never made it into linux-next.

> > The warning is currently disabled in mainline, but this seems

> > to be a legitimate instance, and we may want to turn it back

> > on in the future.

> > ---

> >   drivers/gpu/drm/stm/dw_mipi_dsi-stm.c | 8 +++++---

> >   1 file changed, 5 insertions(+), 3 deletions(-)

> > 

> > diff --git a/drivers/gpu/drm/stm/dw_mipi_dsi-stm.c b/drivers/gpu/drm/stm/dw_mipi_dsi-stm.c

> > index 568c5d0461ea..e5b6310240fe 100644

> > --- a/drivers/gpu/drm/stm/dw_mipi_dsi-stm.c

> > +++ b/drivers/gpu/drm/stm/dw_mipi_dsi-stm.c

> > @@ -113,11 +113,13 @@ static enum dsi_color dsi_color_from_mipi(enum mipi_dsi_pixel_format fmt)

> >   static int dsi_pll_get_clkout_khz(int clkin_khz, int idf, int ndiv, int odf)

> >   {

> > +	int divisor = idf * odf;

> > +

> >   	/* prevent from division by 0 */

> > -	if (idf * odf)

> > -		return DIV_ROUND_CLOSEST(clkin_khz * ndiv, idf * odf);

> > +	if (!divisor)

> > +		return 0;

> > -	return 0;

> > +	return DIV_ROUND_CLOSEST(clkin_khz * ndiv, divisor);

> >   }

> >   static int dsi_pll_get_params(int clkin_khz, int clkout_khz,

> > 

> 

> -- 

> Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,

> a Linux Foundation Collaborative Project

> _______________________________________________

> dri-devel mailing list

> dri-devel@lists.freedesktop.org

> https://lists.freedesktop.org/mailman/listinfo/dri-devel


-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch

Patch

diff --git a/drivers/gpu/drm/stm/dw_mipi_dsi-stm.c b/drivers/gpu/drm/stm/dw_mipi_dsi-stm.c
index 568c5d0461ea..e5b6310240fe 100644
--- a/drivers/gpu/drm/stm/dw_mipi_dsi-stm.c
+++ b/drivers/gpu/drm/stm/dw_mipi_dsi-stm.c
@@ -113,11 +113,13 @@  static enum dsi_color dsi_color_from_mipi(enum mipi_dsi_pixel_format fmt)
 
 static int dsi_pll_get_clkout_khz(int clkin_khz, int idf, int ndiv, int odf)
 {
+	int divisor = idf * odf;
+
 	/* prevent from division by 0 */
-	if (idf * odf)
-		return DIV_ROUND_CLOSEST(clkin_khz * ndiv, idf * odf);
+	if (!divisor)
+		return 0;
 
-	return 0;
+	return DIV_ROUND_CLOSEST(clkin_khz * ndiv, divisor);
 }
 
 static int dsi_pll_get_params(int clkin_khz, int clkout_khz,