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SubjectRe: [PATCH 1/9] drm/panel: simple: add a macro for defining display modes in a simpler and less error prone way
Hi,

On Tue, 17 Oct 2017 14:08:18 +0200 Thierry Reding wrote:
> On Wed, Oct 11, 2017 at 01:23:33PM +0200, Lothar Waßmann wrote:
> > Create a macro that eases the definition of display mode parameters by
> > accecpting the parameters:
> > freq, hactive, hfront-porch, hsynclen, hback-porch,
> > vactive, vfront-porch, vsynclen, vback-porch, vrefresh
> > that can be usually directly taken from an LCD datasheet.
> >
> > Put the calculations that are now open coded repeating the same
> > parameters multiple times into the macro expansion.
> >
> > Signed-off-by: Lothar Waßmann <LW@KARO-electronics.de>
> > ---
> > drivers/gpu/drm/panel/panel-simple.c | 14 ++++++++++++++
> > 1 file changed, 14 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/panel/panel-simple.c b/drivers/gpu/drm/panel/panel-simple.c
> > index 474fa75..dec639d 100644
> > --- a/drivers/gpu/drm/panel/panel-simple.c
> > +++ b/drivers/gpu/drm/panel/panel-simple.c
> > @@ -411,6 +411,20 @@ static const struct panel_desc ampire_am_480272h3tmqw_t01h = {
> > .bus_format = MEDIA_BUS_FMT_RGB888_1X24,
> > };
> >
> > +#define SP_DISPLAY_MODE(freq, ha, hfp, hs, hbp, va, vfp, vs, vbp, vr, flgs) { \
> > + .clock = freq, \
> > + .hdisplay = ha, \
> > + .hsync_start = (ha) + (hfp), \
> > + .hsync_end = (ha) + (hfp) + (hs), \
> > + .htotal = (ha) + (hfp) + (hs) + (hbp), \
> > + .vdisplay = (va), \
> > + .vsync_start = (va) + (vfp), \
> > + .vsync_end = (va) + (vfp) + (vs), \
> > + .vtotal = (va) + (vfp) + (vs) + (vbp), \
> > + .vrefresh = vr, \
> > + .flags = flgs, \
> > + }
>
> I don't think this simplifies anything. It's now completely non-obvious
> which parameter is which, so you actually have to go look at the macro
> definition when you add a new mode to make sure you get them right.
>
In the original code you have to repeat the same parameters (e.g.
vertical front porch (vfp)) in multiple places which is error prone.


Lothar Waßmann

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