linux-kernel - Re: [PATCH 19/20] drm: rcar-du: crtc: Register GAMMA

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Message-ID: <20190614092745.wznk3iv5dgehmjsb@uno.localdomain>
Date:   Fri, 14 Jun 2019 11:27:45 +0200
From:   Jacopo Mondi <jacopo@...ndi.org>
To:     Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Jacopo Mondi <jacopo+renesas@...ndi.org>,
        kieran.bingham+renesas@...asonboard.com, airlied@...ux.ie,
        koji.matsuoka.xm@...esas.com, muroya@....co.jp,
        VenkataRajesh.Kalakodima@...bosch.com,
        Harsha.ManjulaMallikarjun@...bosch.com,
        linux-renesas-soc@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 19/20] drm: rcar-du: crtc: Register GAMMA_LUT properties

Hi Daniel,

On Fri, Jun 14, 2019 at 10:42:51AM +0200, Daniel Vetter wrote:
> On Fri, Jun 14, 2019 at 10:15:52AM +0200, Jacopo Mondi wrote:
> > Hi Laurent,
> >    thanks for review
> >
> > On Fri, Jun 07, 2019 at 03:03:04PM +0300, Laurent Pinchart wrote:
> > > Hi Jacopo,
> > >
> > > Thank you for the patch.
> > >
> > > On Thu, Jun 06, 2019 at 04:22:19PM +0200, Jacopo Mondi wrote:
> > > > Enable the GAMMA_LUT KMS property using the framework helpers to
> > > > register the proeprty and the associated gamma table size maximum size.
> > > >
> > > > Signed-off-by: Jacopo Mondi <jacopo+renesas@...ndi.org>
> > > > ---
> > > >  drivers/gpu/drm/rcar-du/rcar_du_crtc.c | 3 +++
> > > >  1 file changed, 3 insertions(+)
> > > >
> > > > diff --git a/drivers/gpu/drm/rcar-du/rcar_du_crtc.c b/drivers/gpu/drm/rcar-du/rcar_du_crtc.c
> > > > index e6d3df37c827..c920fb5dba65 100644
> > > > --- a/drivers/gpu/drm/rcar-du/rcar_du_crtc.c
> > > > +++ b/drivers/gpu/drm/rcar-du/rcar_du_crtc.c
> > > > @@ -1207,6 +1207,9 @@ int rcar_du_crtc_create(struct rcar_du_group *rgrp, unsigned int swindex,
> > > >  	    rcdu->cmms[swindex]) {
> > > >  		rcrtc->cmm = rcdu->cmms[swindex];
> > > >  		rgrp->cmms_mask |= BIT(hwindex % 2);
> > > > +
> > > > +		drm_mode_crtc_set_gamma_size(crtc, CMM_GAMMA_LUT_SIZE);
> > > > +		drm_crtc_enable_color_mgmt(crtc, 0, false, CMM_GAMMA_LUT_SIZE);
> > >
> > > This change looks good, but you also need to add support for legacy API.
> > > According to the function's documentation,
> > >
> > >  * Drivers should use drm_atomic_helper_legacy_gamma_set() to implement the
> > >  * legacy &drm_crtc_funcs.gamma_set callback.
> > >
> >
> > Drivers 'shuld' or drivers 'shall' ?
> > Isn't this required only to support the 'legacy APIs' ? Do we want that?
>
> You're calling drm_mode_crtc_set_gamma_size, which is only useful for the
> legacy ioctls. should here = assuming your hw supports something that
> legacy gamma ioctl can use. Feel free to patch up the docs.

Oh, I see. I should either leave the old API alone without calling
drm_mode_crtc_set_gamma_size(), or set the .gamma_set callback to
point to drm_atomic_helper_legacy_gamma_set(), which translates the
old gamma table interface to a blob property and attach it to a crtc
state which is then commited and applied through the atomic helpers.

So I would change the doc to prescribe that if the driver intends to
support the legacy SETGAMMA/GETGAMMA IOCTLs it should declare the
gamma table size with drm_mode_crtc_set_gamma_size() first, and set
the .gamma_set crtc callback to drm_atomic_helper_legacy_gamma_set(),
which translates the legacy interface to a GAMMA_LUT property blob
and commit it.

If that works, I'll make a small patch to the documentation in v2.

Thanks
  j


> -Daniel
>
> >
> > Thanks
> >    j
> >
> > > >  	}
> > > >
> > > >  	drm_crtc_helper_add(crtc, &crtc_helper_funcs);
> > > >
> > >
> > > --
> > > Regards,
> > >
> > > Laurent Pinchart
>
>
>
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch

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