Hi Thomas.
On Mon, Mar 30, 2020 at 01:29:16PM +0200, Thomas Zimmermann wrote:
> Hi Sam and Lyude,
>
> thanks for improving the documentation. Below are a few points that I'd
> found more understandable. I'm no native speaker, though.
>
> Am 28.03.20 um 14:20 schrieb Sam Ravnborg:
> > Lyude Paul wrote a very good intro to vblank here:
> > https://lore.kernel.org/dri-devel/[email protected]/T/#mce6480be738160e9d07c5d023e88fd78d7a06d27
> >
> > Add this to the intro chapter in drm_vblank.c so others
> > can benefit from it too.
> >
> > Signed-off-by: Sam Ravnborg <[email protected]>
> > Co-developed-by: Lyude Paul <[email protected]>
> > Cc: Lyude Paul <[email protected]>
> > Cc: Daniel Vetter <[email protected]>
> > Cc: Maarten Lankhorst <[email protected]>
> > Cc: Maxime Ripard <[email protected]>
> > Cc: Thomas Zimmermann <[email protected]>
> > Cc: David Airlie <[email protected]>
> > ---
> > drivers/gpu/drm/drm_vblank.c | 15 +++++++++++++++
> > 1 file changed, 15 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c
> > index bcf346b3e486..95cac22d59d1 100644
> > --- a/drivers/gpu/drm/drm_vblank.c
> > +++ b/drivers/gpu/drm/drm_vblank.c
> > @@ -41,6 +41,21 @@
> > /**
> > * DOC: vblank handling
> > *
> > + * From the perspective of a computer, every time a computer monitor
> > displays
>
> Possibly change from dative case to genitive:
>
> "From the computer's perspective," ...
>
> > + * a new frame it's done by "scanning out" the display image from top to
> > + * bottom, one row of pixels at a time. which row of pixels we're on is
>
> s/which/Which
>
> The text changes from third person (the computer) to first person
> (we're). Makes it harder to read. I'd remove both, "we" and "computer",
> and speak of display hardware or scanout engine.
>
> > + * referred to as the scanline.
>
> I'd say a scanline is any of them. Maybe say "current scanline"?
>
> > + * Additionally, there's usually a couple of extra scanlines which we
>
> "In addition to the display's visible area, there's usually a couple of
> extra scanlines that" ...
>
> > + * scan out, but aren't actually displayed on the screen (these sometimes
> > + * get used by HDMI audio and friends, but that's another story).
> > + * The period where we're on these scanlines is referred to as the vblank.
>
> I'd replace vblank with "vertical blanking period." That term is
> required in the next paragraph.
>
> The time when the hardware operates on these invisible scanlines is
> referred to as vertical blanking period, or simply vblank.
>
> > + *
> > + * On a lot of display hardware, programming needs to take effect during
> > the
> > + * vertical blanking period so that settings like gamma, what frame we're
>
> "we" again
>
> > + * scanning out, etc. can be safely changed without showing visual tearing
> > + * on the screen. In some unforgiving hardware, some of this programming
> > has
> > + * to both start and end in the same vblank - vertical blanking.
> > + *
> > * Vertical blanking plays a major role in graphics rendering. To achieve
> > * tear-free display, users must synchronize page flips and/or rendering to
> > * vertical blanking. The DRM API offers ioctls to perform page flips
> >
>
> In any case
>
> Acked-by: Thomas Zimmermann <[email protected]>
Thanks for the detailed feedabck - I have tried to reword it so it
better fits the context and have taking into account your suggetions.
See other mail for the updated patch.
Sam
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