From: Daniel Vetter <daniel@ffwll.ch>
To: Stefan Agner <stefan@agner.ch>
Cc: jianwei.wang.chn@gmail.com, Meng Yi <meng.yi@nxp.com>,
dri-devel@lists.freedesktop.org
Subject: Re: [PATCH v3] drm/fsl-dcu: Implement gamma_lut atomic crtc properties
Date: Thu, 22 Sep 2016 08:29:21 +0200 [thread overview]
Message-ID: <20160922062921.GB22164@dvetter-linux.ger.corp.intel.com> (raw)
In-Reply-To: <5f4840de93ad0049d6b05910a8ebf537@agner.ch>
On Wed, Sep 21, 2016 at 11:10:11AM -0700, Stefan Agner wrote:
> On 2016-09-13 01:49, Meng Yi wrote:
> >> > diff --git a/drivers/gpu/drm/fsl-dcu/Kconfig
> >> > b/drivers/gpu/drm/fsl-dcu/Kconfig index 14a72c4..f9c76b1 100644
> >> > --- a/drivers/gpu/drm/fsl-dcu/Kconfig
> >> > +++ b/drivers/gpu/drm/fsl-dcu/Kconfig
> >> > @@ -11,3 +11,9 @@ config DRM_FSL_DCU
> >> > help
> >> > Choose this option if you have an Freescale DCU chipset.
> >> > If M is selected the module will be called fsl-dcu-drm.
> >> > +
> >> > +config DRM_FSL_DCU_GAMMA
> >> > + bool "Gamma Correction Support for NXP/Freescale DCU"
> >> > + depends on DRM_FSL_DCU
> >> > + help
> >> > + Enable support for gamma correction.
> >>
> >> What is the reason for making this a configuration option? Are there
> >> implementation without support for the Gamma tables?
> >>
> > When gamma correction is enabled, the color won't display normally since
> > The gamma tables are not filled with correct data. So I give a choice
> > to not using
> > The gamma correction when you don't want to use it.
> >
> > Should I remove this configuration?
>
> Yeah making this a compile time configuration seems wrong to me.
>
> I guess we should fill the table with a reasonable default then. The
> omapdrm driver seems to do something similar.
Yup Kconfig is definitely not the correct way to fix a setup problem in
your driver. Note that even when you enable gamma lut userspace is allowed
to set a NULL table, and in that case you need to either disable the gamma
lut, or fill it with a 1:1 mapping (if you hw doesn't have a disable
flag). At boot-up the table will also be NULL (except when you have
special setup code), and if that results in a black screen your driver is
buggy. Papering over a driver bug with Kconfig is definitely not ok.
-Daniel
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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next prev parent reply other threads:[~2016-09-22 16:08 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-07 9:22 [PATCH v3] drm/fsl-dcu: Implement gamma_lut atomic crtc properties Meng Yi
2016-09-07 17:05 ` Stefan Agner
2016-09-08 2:45 ` Meng Yi
2016-09-13 7:02 ` Stefan Agner
2016-09-13 8:49 ` Meng Yi
2016-09-21 18:10 ` Stefan Agner
2016-09-22 6:29 ` Daniel Vetter [this message]
2016-09-26 6:04 ` Meng Yi
2016-09-26 7:59 ` Daniel Vetter
2016-09-26 8:17 ` Ville Syrjälä
2016-09-26 19:33 ` Stefan Agner
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