Re: [PATCH v3 06/14] Documentation: drm/bridge: add document for analogix_dp

[Yakir Yang]

Hi Heiko,

å 2015/8/24 21:03, Heiko Stuebner åé:
> Hi Yakir,
>
> Am Montag, 24. August 2015, 20:48:01 schrieb Yakir Yang:
> > å 08/24/2015 12:20 PM, Krzysztof Kozlowski åé:
> > > On 24.08.2015 11:42, Yakir Yang wrote:
> > > > Hi Krzysztof,
> > > >
> > > > å 08/23/2015 07:43 PM, Krzysztof Kozlowski åé:
> > > > > 2015-08-24 8:23 GMT+09:00 Rob Herring <robherring2@xxxxxxxxx>:
> > > > > > On Wed, Aug 19, 2015 at 9:50 AM, Yakir Yang <ykk@xxxxxxxxxxxxxx> wrote:
> > > > > > > Analogix dp driver is split from exynos dp driver, so we just
> > > > > > > make an copy of exynos_dp.txt, and then simplify exynos_dp.txt
> > > > > > >
> > > > > > > Beside update some exynos dtsi file with the latest change
> > > > > > > according to the devicetree binding documents.
> > > > > > You can't just change the exynos bindings and break compatibility. Is
> > > > > > there some agreement with exynos folks to do this?
> > > > > No, there is no agreement. This wasn't even sent to Exynos maintainers.
> > > > Sorry about this one, actually I have add Exynos maintainers in version
> > > > 1 & version 2,
> > > > but lose some maintainers in version 3, I would fix it in bellow
> > > > versions.
> > > >
> > > > > Additionally the patchset did not look interesting to me because of
> > > > > misleading subject - Documentation instead of "ARM: dts:".
> > > > >
> > > > > Yakir, please:
> > > > > 1. Provide backward compatibility. Mark old properties as deprecated
> > > > > but still support them.
> > > > Do you mean that I should keep the old properties declare in
> > > > exynos-dp.txt,
> > > > but just mark them as deprecated flag.
> > > That is one of ways how to do this. However more important is that
> > > driver should still support old bindings so such code:
> > > -       if (of_property_read_u32(dp_node, "samsung,color-space",
> > > +       if (of_property_read_u32(dp_node, "analogix,color-space",
> > >
> > > is probably wrong. Will the driver support old DTB in the same way as it
> > > was supporting before the change?
> > Okay, I got your means. So document is not the focus, the most important
> > is that
> > driver should support the old dts prop. If so the new analogix dp driver
> > should keep
> > the "samsung,color-space", rather then just mark it with [DEPRECATED] flag.
> >
> > But from your follow suggest, I think you agree to update driver code,
> > and just mark
> > old prop with deprecated flag. If so I think such code would not be wrong
> >
> > -       if (of_property_read_u32(dp_node, "samsung,color-space",
> > +      if (of_property_read_u32(dp_node, "analogix,color-space",
> In a generic driver, the property should have either none, or the analogix
> prefix. But DT-properties need to be backwards compatible, meaning an older
> Exynos devicetree should run unmodified with a newer kernel.
>
> So the common course of action is to mark the old one as deprecated but still
> test for both, so something like:
>
>         if (of_property_read_u32(dp_node, "analogix,color-space",
>                                   &dp_video_config->color_space))
> 	       if (of_property_read_u32(dp_node, "samsung,color-space",
>                  	                 &dp_video_config->color_space)) {
>
>                  	dev_err(dev, "failed to get color-space\n");
>                  	return ERR_PTR(-EINVAL);
>          	}

Wow, thanks a lot for your explain and code, it do help me to understand
this suggest rightly  :-)

Thanks,
- Yakir

>


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