media: renesas: rzg2l-cru: Simplify FIFO empty check

[PATCH] media: renesas: rzg2l-cru: Simplify FIFO empty check

Posted by Prabhakar 9 months, 2 weeks ago

From: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>

Simplify the `rzg2l_fifo_empty()` helper by removing the redundant
comparison in the return path. Now the function explicitly returns `true`
if the FIFO write and read pointers match, and `false` otherwise, improving
readability without changing behavior.

Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Closes: https://lore.kernel.org/all/aAtQThCibZCROETx@stanley.mountain/
Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
---
 drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c b/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
index 067c6af14e95..97faefcd6019 100644
--- a/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
+++ b/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
@@ -348,7 +348,7 @@ bool rzg2l_fifo_empty(struct rzg2l_cru_dev *cru)
 	if (amnfifopntr_w == amnfifopntr_r_y)
 		return true;
 
-	return amnfifopntr_w == amnfifopntr_r_y;
+	return false;
 }
 
 void rzg2l_cru_stop_image_processing(struct rzg2l_cru_dev *cru)
-- 
2.49.0

Re: [PATCH] media: renesas: rzg2l-cru: Simplify FIFO empty check

Posted by Laurent Pinchart 9 months, 2 weeks ago

Hi Prabhakar,

Thank you for the patch.

On Mon, Apr 28, 2025 at 10:52:08AM +0100, Prabhakar wrote:
> From: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
> 
> Simplify the `rzg2l_fifo_empty()` helper by removing the redundant
> comparison in the return path. Now the function explicitly returns `true`
> if the FIFO write and read pointers match, and `false` otherwise, improving
> readability without changing behavior.
> 
> Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
> Closes: https://lore.kernel.org/all/aAtQThCibZCROETx@stanley.mountain/
> Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
> ---
>  drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c b/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
> index 067c6af14e95..97faefcd6019 100644
> --- a/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
> +++ b/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
> @@ -348,7 +348,7 @@ bool rzg2l_fifo_empty(struct rzg2l_cru_dev *cru)
>  	if (amnfifopntr_w == amnfifopntr_r_y)
>  		return true;
>  
> -	return amnfifopntr_w == amnfifopntr_r_y;
> +	return false;

So the function always returned true. This seems to be a bug fix, please
add a Fixes: tag. The commit message should also make it clear that
you're fixing an issue, not just simplifying the code.

Personally I'd have written

diff --git a/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c b/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
index 067c6af14e95..3d0810b3c35e 100644
--- a/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
+++ b/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
@@ -345,8 +345,6 @@ bool rzg2l_fifo_empty(struct rzg2l_cru_dev *cru)
 	amnfifopntr_w = amnfifopntr & AMnFIFOPNTR_FIFOWPNTR;
 	amnfifopntr_r_y =
 		(amnfifopntr & AMnFIFOPNTR_FIFORPNTR_Y) >> 16;
-	if (amnfifopntr_w == amnfifopntr_r_y)
-		return true;

 	return amnfifopntr_w == amnfifopntr_r_y;
 }

but that's also a bit of a style preference.

>  }
>  
>  void rzg2l_cru_stop_image_processing(struct rzg2l_cru_dev *cru)

-- 
Regards,

Laurent Pinchart

Re: [PATCH] media: renesas: rzg2l-cru: Simplify FIFO empty check

Posted by Lad, Prabhakar 9 months, 2 weeks ago

Hi Laurent,

Thank you for the review.

On Mon, Apr 28, 2025 at 10:59 AM Laurent Pinchart
<laurent.pinchart@ideasonboard.com> wrote:
>
> Hi Prabhakar,
>
> Thank you for the patch.
>
> On Mon, Apr 28, 2025 at 10:52:08AM +0100, Prabhakar wrote:
> > From: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
> >
> > Simplify the `rzg2l_fifo_empty()` helper by removing the redundant
> > comparison in the return path. Now the function explicitly returns `true`
> > if the FIFO write and read pointers match, and `false` otherwise, improving
> > readability without changing behavior.
> >
> > Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
> > Closes: https://lore.kernel.org/all/aAtQThCibZCROETx@stanley.mountain/
> > Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
> > ---
> >  drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c b/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
> > index 067c6af14e95..97faefcd6019 100644
> > --- a/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
> > +++ b/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
> > @@ -348,7 +348,7 @@ bool rzg2l_fifo_empty(struct rzg2l_cru_dev *cru)
> >       if (amnfifopntr_w == amnfifopntr_r_y)
> >               return true;
> >
> > -     return amnfifopntr_w == amnfifopntr_r_y;
> > +     return false;
>
> So the function always returned true. This seems to be a bug fix, please
> add a Fixes: tag. The commit message should also make it clear that
> you're fixing an issue, not just simplifying the code.
>
No, the function returned true only if the pointers matched;
otherwise, amnfifopntr_w == amnfifopntr_r_y would return false. I was
simply removing the repetitive pointer check and directly returning
false at the end of the function, as we can be certain at that point.
Hence, I did not add a Fixes tag. Am I missing something?

> Personally I'd have written
>
> diff --git a/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c b/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
> index 067c6af14e95..3d0810b3c35e 100644
> --- a/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
> +++ b/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
> @@ -345,8 +345,6 @@ bool rzg2l_fifo_empty(struct rzg2l_cru_dev *cru)
>         amnfifopntr_w = amnfifopntr & AMnFIFOPNTR_FIFOWPNTR;
>         amnfifopntr_r_y =
>                 (amnfifopntr & AMnFIFOPNTR_FIFORPNTR_Y) >> 16;
> -       if (amnfifopntr_w == amnfifopntr_r_y)
> -               return true;
>
>         return amnfifopntr_w == amnfifopntr_r_y;
>  }
>
> but that's also a bit of a style preference.
>
I wanted to keep this consistent with the rz3e_fifo_empty(). If you
prefer the above I'll do that in v2.

Cheers,
Prabhakar

Re: [PATCH] media: renesas: rzg2l-cru: Simplify FIFO empty check

Posted by Laurent Pinchart 9 months, 2 weeks ago

On Mon, Apr 28, 2025 at 12:17:54PM +0100, Lad, Prabhakar wrote:
> On Mon, Apr 28, 2025 at 10:59 AM Laurent Pinchart wrote:
> > On Mon, Apr 28, 2025 at 10:52:08AM +0100, Prabhakar wrote:
> > > From: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
> > >
> > > Simplify the `rzg2l_fifo_empty()` helper by removing the redundant
> > > comparison in the return path. Now the function explicitly returns `true`
> > > if the FIFO write and read pointers match, and `false` otherwise, improving
> > > readability without changing behavior.
> > >
> > > Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
> > > Closes: https://lore.kernel.org/all/aAtQThCibZCROETx@stanley.mountain/
> > > Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
> > > ---
> > >  drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c b/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
> > > index 067c6af14e95..97faefcd6019 100644
> > > --- a/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
> > > +++ b/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
> > > @@ -348,7 +348,7 @@ bool rzg2l_fifo_empty(struct rzg2l_cru_dev *cru)
> > >       if (amnfifopntr_w == amnfifopntr_r_y)
> > >               return true;
> > >
> > > -     return amnfifopntr_w == amnfifopntr_r_y;
> > > +     return false;
> >
> > So the function always returned true. This seems to be a bug fix, please
> > add a Fixes: tag. The commit message should also make it clear that
> > you're fixing an issue, not just simplifying the code.
>
> No, the function returned true only if the pointers matched;
> otherwise, amnfifopntr_w == amnfifopntr_r_y would return false. I was
> simply removing the repetitive pointer check and directly returning
> false at the end of the function, as we can be certain at that point.
> Hence, I did not add a Fixes tag. Am I missing something?

Oops, you're right, my bad.

> > Personally I'd have written
> >
> > diff --git a/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c b/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
> > index 067c6af14e95..3d0810b3c35e 100644
> > --- a/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
> > +++ b/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
> > @@ -345,8 +345,6 @@ bool rzg2l_fifo_empty(struct rzg2l_cru_dev *cru)
> >         amnfifopntr_w = amnfifopntr & AMnFIFOPNTR_FIFOWPNTR;
> >         amnfifopntr_r_y =
> >                 (amnfifopntr & AMnFIFOPNTR_FIFORPNTR_Y) >> 16;
> > -       if (amnfifopntr_w == amnfifopntr_r_y)
> > -               return true;
> >
> >         return amnfifopntr_w == amnfifopntr_r_y;
> >  }
> >
> > but that's also a bit of a style preference.
>
> I wanted to keep this consistent with the rz3e_fifo_empty(). If you
> prefer the above I'll do that in v2.

Up to you.

-- 
Regards,

Laurent Pinchart

Re: [PATCH] media: renesas: rzg2l-cru: Simplify FIFO empty check

Posted by Lad, Prabhakar 9 months, 2 weeks ago

Hi Laurent,

On Mon, Apr 28, 2025 at 12:25 PM Laurent Pinchart
<laurent.pinchart@ideasonboard.com> wrote:
>
> On Mon, Apr 28, 2025 at 12:17:54PM +0100, Lad, Prabhakar wrote:
> > On Mon, Apr 28, 2025 at 10:59 AM Laurent Pinchart wrote:
> > > On Mon, Apr 28, 2025 at 10:52:08AM +0100, Prabhakar wrote:
> > > > From: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
> > > >
> > > > Simplify the `rzg2l_fifo_empty()` helper by removing the redundant
> > > > comparison in the return path. Now the function explicitly returns `true`
> > > > if the FIFO write and read pointers match, and `false` otherwise, improving
> > > > readability without changing behavior.
> > > >
> > > > Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
> > > > Closes: https://lore.kernel.org/all/aAtQThCibZCROETx@stanley.mountain/
> > > > Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
> > > > ---
> > > >  drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c | 2 +-
> > > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > >
> > > > diff --git a/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c b/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
> > > > index 067c6af14e95..97faefcd6019 100644
> > > > --- a/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
> > > > +++ b/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
> > > > @@ -348,7 +348,7 @@ bool rzg2l_fifo_empty(struct rzg2l_cru_dev *cru)
> > > >       if (amnfifopntr_w == amnfifopntr_r_y)
> > > >               return true;
> > > >
> > > > -     return amnfifopntr_w == amnfifopntr_r_y;
> > > > +     return false;
> > >
> > > So the function always returned true. This seems to be a bug fix, please
> > > add a Fixes: tag. The commit message should also make it clear that
> > > you're fixing an issue, not just simplifying the code.
> >
> > No, the function returned true only if the pointers matched;
> > otherwise, amnfifopntr_w == amnfifopntr_r_y would return false. I was
> > simply removing the repetitive pointer check and directly returning
> > false at the end of the function, as we can be certain at that point.
> > Hence, I did not add a Fixes tag. Am I missing something?
>
> Oops, you're right, my bad.
>
> > > Personally I'd have written
> > >
> > > diff --git a/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c b/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
> > > index 067c6af14e95..3d0810b3c35e 100644
> > > --- a/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
> > > +++ b/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
> > > @@ -345,8 +345,6 @@ bool rzg2l_fifo_empty(struct rzg2l_cru_dev *cru)
> > >         amnfifopntr_w = amnfifopntr & AMnFIFOPNTR_FIFOWPNTR;
> > >         amnfifopntr_r_y =
> > >                 (amnfifopntr & AMnFIFOPNTR_FIFORPNTR_Y) >> 16;
> > > -       if (amnfifopntr_w == amnfifopntr_r_y)
> > > -               return true;
> > >
> > >         return amnfifopntr_w == amnfifopntr_r_y;
> > >  }
> > >
> > > but that's also a bit of a style preference.
> >
> > I wanted to keep this consistent with the rz3e_fifo_empty(). If you
> > prefer the above I'll do that in v2.
>
> Up to you.
>
Thanks. OK, let's keep this patch as is to stay consistent with
rz3e_fifo_empty().

Cheers,
Prabhakar

Re: [PATCH] media: renesas: rzg2l-cru: Simplify FIFO empty check

Posted by Geert Uytterhoeven 9 months, 2 weeks ago

Hi Prabhakar,

On Mon, 28 Apr 2025 at 13:33, Lad, Prabhakar <prabhakar.csengg@gmail.com> wrote:
> On Mon, Apr 28, 2025 at 12:25 PM Laurent Pinchart
> <laurent.pinchart@ideasonboard.com> wrote:
> > On Mon, Apr 28, 2025 at 12:17:54PM +0100, Lad, Prabhakar wrote:
> > > On Mon, Apr 28, 2025 at 10:59 AM Laurent Pinchart wrote:
> > > > On Mon, Apr 28, 2025 at 10:52:08AM +0100, Prabhakar wrote:
> > > > > From: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
> > > > >
> > > > > Simplify the `rzg2l_fifo_empty()` helper by removing the redundant
> > > > > comparison in the return path. Now the function explicitly returns `true`
> > > > > if the FIFO write and read pointers match, and `false` otherwise, improving
> > > > > readability without changing behavior.
> > > > >
> > > > > Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
> > > > > Closes: https://lore.kernel.org/all/aAtQThCibZCROETx@stanley.mountain/
> > > > > Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
> > > > > ---
> > > > >  drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c | 2 +-
> > > > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > > >
> > > > > diff --git a/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c b/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
> > > > > index 067c6af14e95..97faefcd6019 100644
> > > > > --- a/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
> > > > > +++ b/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
> > > > > @@ -348,7 +348,7 @@ bool rzg2l_fifo_empty(struct rzg2l_cru_dev *cru)
> > > > >       if (amnfifopntr_w == amnfifopntr_r_y)
> > > > >               return true;
> > > > >
> > > > > -     return amnfifopntr_w == amnfifopntr_r_y;
> > > > > +     return false;
> > > >
> > > > So the function always returned true. This seems to be a bug fix, please
> > > > add a Fixes: tag. The commit message should also make it clear that
> > > > you're fixing an issue, not just simplifying the code.
> > >
> > > No, the function returned true only if the pointers matched;
> > > otherwise, amnfifopntr_w == amnfifopntr_r_y would return false. I was
> > > simply removing the repetitive pointer check and directly returning
> > > false at the end of the function, as we can be certain at that point.
> > > Hence, I did not add a Fixes tag. Am I missing something?
> >
> > Oops, you're right, my bad.
> >
> > > > Personally I'd have written
> > > >
> > > > diff --git a/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c b/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
> > > > index 067c6af14e95..3d0810b3c35e 100644
> > > > --- a/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
> > > > +++ b/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
> > > > @@ -345,8 +345,6 @@ bool rzg2l_fifo_empty(struct rzg2l_cru_dev *cru)
> > > >         amnfifopntr_w = amnfifopntr & AMnFIFOPNTR_FIFOWPNTR;
> > > >         amnfifopntr_r_y =
> > > >                 (amnfifopntr & AMnFIFOPNTR_FIFORPNTR_Y) >> 16;
> > > > -       if (amnfifopntr_w == amnfifopntr_r_y)
> > > > -               return true;
> > > >
> > > >         return amnfifopntr_w == amnfifopntr_r_y;
> > > >  }
> > > >
> > > > but that's also a bit of a style preference.
> > >
> > > I wanted to keep this consistent with the rz3e_fifo_empty(). If you
> > > prefer the above I'll do that in v2.
> >
> > Up to you.
> >
> Thanks. OK, let's keep this patch as is to stay consistent with
> rz3e_fifo_empty().

rz3e_fifo_empty() has a rather complex conditional expression.

This one will probably be converted to a simple return statement by
a random janitor, soon after its introduction ;-)

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

Re: [PATCH] media: renesas: rzg2l-cru: Simplify FIFO empty check

Posted by Lad, Prabhakar 9 months, 2 weeks ago

Hi Geert,

On Mon, Apr 28, 2025 at 12:36 PM Geert Uytterhoeven
<geert@linux-m68k.org> wrote:
>
> Hi Prabhakar,
>
> On Mon, 28 Apr 2025 at 13:33, Lad, Prabhakar <prabhakar.csengg@gmail.com> wrote:
> > On Mon, Apr 28, 2025 at 12:25 PM Laurent Pinchart
> > <laurent.pinchart@ideasonboard.com> wrote:
> > > On Mon, Apr 28, 2025 at 12:17:54PM +0100, Lad, Prabhakar wrote:
> > > > On Mon, Apr 28, 2025 at 10:59 AM Laurent Pinchart wrote:
> > > > > On Mon, Apr 28, 2025 at 10:52:08AM +0100, Prabhakar wrote:
> > > > > > From: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
> > > > > >
> > > > > > Simplify the `rzg2l_fifo_empty()` helper by removing the redundant
> > > > > > comparison in the return path. Now the function explicitly returns `true`
> > > > > > if the FIFO write and read pointers match, and `false` otherwise, improving
> > > > > > readability without changing behavior.
> > > > > >
> > > > > > Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
> > > > > > Closes: https://lore.kernel.org/all/aAtQThCibZCROETx@stanley.mountain/
> > > > > > Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
> > > > > > ---
> > > > > >  drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c | 2 +-
> > > > > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > > > >
> > > > > > diff --git a/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c b/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
> > > > > > index 067c6af14e95..97faefcd6019 100644
> > > > > > --- a/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
> > > > > > +++ b/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
> > > > > > @@ -348,7 +348,7 @@ bool rzg2l_fifo_empty(struct rzg2l_cru_dev *cru)
> > > > > >       if (amnfifopntr_w == amnfifopntr_r_y)
> > > > > >               return true;
> > > > > >
> > > > > > -     return amnfifopntr_w == amnfifopntr_r_y;
> > > > > > +     return false;
> > > > >
> > > > > So the function always returned true. This seems to be a bug fix, please
> > > > > add a Fixes: tag. The commit message should also make it clear that
> > > > > you're fixing an issue, not just simplifying the code.
> > > >
> > > > No, the function returned true only if the pointers matched;
> > > > otherwise, amnfifopntr_w == amnfifopntr_r_y would return false. I was
> > > > simply removing the repetitive pointer check and directly returning
> > > > false at the end of the function, as we can be certain at that point.
> > > > Hence, I did not add a Fixes tag. Am I missing something?
> > >
> > > Oops, you're right, my bad.
> > >
> > > > > Personally I'd have written
> > > > >
> > > > > diff --git a/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c b/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
> > > > > index 067c6af14e95..3d0810b3c35e 100644
> > > > > --- a/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
> > > > > +++ b/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
> > > > > @@ -345,8 +345,6 @@ bool rzg2l_fifo_empty(struct rzg2l_cru_dev *cru)
> > > > >         amnfifopntr_w = amnfifopntr & AMnFIFOPNTR_FIFOWPNTR;
> > > > >         amnfifopntr_r_y =
> > > > >                 (amnfifopntr & AMnFIFOPNTR_FIFORPNTR_Y) >> 16;
> > > > > -       if (amnfifopntr_w == amnfifopntr_r_y)
> > > > > -               return true;
> > > > >
> > > > >         return amnfifopntr_w == amnfifopntr_r_y;
> > > > >  }
> > > > >
> > > > > but that's also a bit of a style preference.
> > > >
> > > > I wanted to keep this consistent with the rz3e_fifo_empty(). If you
> > > > prefer the above I'll do that in v2.
> > >
> > > Up to you.
> > >
> > Thanks. OK, let's keep this patch as is to stay consistent with
> > rz3e_fifo_empty().
>
> rz3e_fifo_empty() has a rather complex conditional expression.
>
Hmm yes.

> This one will probably be converted to a simple return statement by
> a random janitor, soon after its introduction ;-)
>
Agreed, are you already working on it?

Cheers,
Prabhakar

Re: [PATCH] media: renesas: rzg2l-cru: Simplify FIFO empty check

Posted by Geert Uytterhoeven 9 months, 2 weeks ago

Hi Prabhakar,

On Mon, 28 Apr 2025 at 15:25, Lad, Prabhakar <prabhakar.csengg@gmail.com> wrote:
> On Mon, Apr 28, 2025 at 12:36 PM Geert Uytterhoeven
> <geert@linux-m68k.org> wrote:
> > On Mon, 28 Apr 2025 at 13:33, Lad, Prabhakar <prabhakar.csengg@gmail.com> wrote:
> > > On Mon, Apr 28, 2025 at 12:25 PM Laurent Pinchart
> > > <laurent.pinchart@ideasonboard.com> wrote:
> > > > On Mon, Apr 28, 2025 at 12:17:54PM +0100, Lad, Prabhakar wrote:
> > > > > On Mon, Apr 28, 2025 at 10:59 AM Laurent Pinchart wrote:
> > > > > > On Mon, Apr 28, 2025 at 10:52:08AM +0100, Prabhakar wrote:
> > > > > > > From: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
> > > > > > >
> > > > > > > Simplify the `rzg2l_fifo_empty()` helper by removing the redundant
> > > > > > > comparison in the return path. Now the function explicitly returns `true`
> > > > > > > if the FIFO write and read pointers match, and `false` otherwise, improving
> > > > > > > readability without changing behavior.
> > > > > > >
> > > > > > > Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
> > > > > > > Closes: https://lore.kernel.org/all/aAtQThCibZCROETx@stanley.mountain/
> > > > > > > Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
> > > > > > > ---
> > > > > > >  drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c | 2 +-
> > > > > > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > > > > >
> > > > > > > diff --git a/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c b/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
> > > > > > > index 067c6af14e95..97faefcd6019 100644
> > > > > > > --- a/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
> > > > > > > +++ b/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
> > > > > > > @@ -348,7 +348,7 @@ bool rzg2l_fifo_empty(struct rzg2l_cru_dev *cru)
> > > > > > >       if (amnfifopntr_w == amnfifopntr_r_y)
> > > > > > >               return true;
> > > > > > >
> > > > > > > -     return amnfifopntr_w == amnfifopntr_r_y;
> > > > > > > +     return false;
> > > > > >
> > > > > > So the function always returned true. This seems to be a bug fix, please
> > > > > > add a Fixes: tag. The commit message should also make it clear that
> > > > > > you're fixing an issue, not just simplifying the code.
> > > > >
> > > > > No, the function returned true only if the pointers matched;
> > > > > otherwise, amnfifopntr_w == amnfifopntr_r_y would return false. I was
> > > > > simply removing the repetitive pointer check and directly returning
> > > > > false at the end of the function, as we can be certain at that point.
> > > > > Hence, I did not add a Fixes tag. Am I missing something?
> > > >
> > > > Oops, you're right, my bad.
> > > >
> > > > > > Personally I'd have written
> > > > > >
> > > > > > diff --git a/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c b/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
> > > > > > index 067c6af14e95..3d0810b3c35e 100644
> > > > > > --- a/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
> > > > > > +++ b/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
> > > > > > @@ -345,8 +345,6 @@ bool rzg2l_fifo_empty(struct rzg2l_cru_dev *cru)
> > > > > >         amnfifopntr_w = amnfifopntr & AMnFIFOPNTR_FIFOWPNTR;
> > > > > >         amnfifopntr_r_y =
> > > > > >                 (amnfifopntr & AMnFIFOPNTR_FIFORPNTR_Y) >> 16;
> > > > > > -       if (amnfifopntr_w == amnfifopntr_r_y)
> > > > > > -               return true;
> > > > > >
> > > > > >         return amnfifopntr_w == amnfifopntr_r_y;
> > > > > >  }
> > > > > >
> > > > > > but that's also a bit of a style preference.
> > > > >
> > > > > I wanted to keep this consistent with the rz3e_fifo_empty(). If you
> > > > > prefer the above I'll do that in v2.
> > > >
> > > > Up to you.
> > > >
> > > Thanks. OK, let's keep this patch as is to stay consistent with
> > > rz3e_fifo_empty().
> >
> > rz3e_fifo_empty() has a rather complex conditional expression.
> >
> Hmm yes.
>
> > This one will probably be converted to a simple return statement by
> > a random janitor, soon after its introduction ;-)
> >
> Agreed, are you already working on it?

Nice try ;-)

-EBUSY.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds