Re: [PATCH] drm/drm_vblank.c: avoid unsigned int to signed int cast

[Sui Jingfeng]

Hi,

On 2023/5/17 01:06, Thomas Zimmermann wrote:
> Am 16.05.23 um 18:59 schrieb Sui Jingfeng:
> > Both mode->crtc_htotal and mode->crtc_vtotal are u16 type,
> > mode->crtc_htotal * mode->crtc_vtotal will results a unsigned type.
> > Using a u32 is enough to store the result, but considering that the
> > result will be casted to u64 soon after. We use a u64 type directly.
> >
> > So there no need to cast it to signed type and cast back then.
> >
> > Signed-off-by: Sui Jingfeng <suijingfeng@xxxxxxxxxxx>
> > Cc: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx>
> > Cc: Maxime Ripard <mripard@xxxxxxxxxx>
> > Cc: Thomas Zimmermann <tzimmermann@xxxxxxx>
> > Cc: David Airlie <airlied@xxxxxxxxx>
> > Cc: Daniel Vetter <daniel@xxxxxxxx>
> > Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx
> > Cc: linux-kernel@xxxxxxxxxxxxxxx
>
> Reviewed-by: Thomas Zimmermann <tzimmermann@xxxxxxx>
Thanks a lot,  thanks for the response time also.

> > ---
> >   drivers/gpu/drm/drm_vblank.c | 4 ++--
> >   1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c
> > index 877e2067534f..d99c404b181b 100644
> > --- a/drivers/gpu/drm/drm_vblank.c
> > +++ b/drivers/gpu/drm/drm_vblank.c
> > @@ -622,7 +622,7 @@ void drm_calc_timestamping_constants(struct 
> > drm_crtc *crtc,
> >         /* Valid dotclock? */
> >       if (dotclock > 0) {
> > -        int frame_size = mode->crtc_htotal * mode->crtc_vtotal;
> > +        u64 frame_size = mode->crtc_htotal * mode->crtc_vtotal;
> >             /*
> >            * Convert scanline length in pixels and video
> > @@ -630,7 +630,7 @@ void drm_calc_timestamping_constants(struct 
> > drm_crtc *crtc,
> >            * in nanoseconds:
> >            */
> >           linedur_ns  = div_u64((u64) mode->crtc_htotal * 1000000, 
> > dotclock);
> > -        framedur_ns = div_u64((u64) frame_size * 1000000, dotclock);
> > +        framedur_ns = div_u64(frame_size * 1000000, dotclock);
> >             /*
> >            * Fields of interlaced scanout modes are only half a frame 
> > duration.