Date:   Fri, 21 Oct 2016 14:19:51 +0200
From:   Daniel Vetter <daniel@...ll.ch>
To:     Jani Nikula <jani.nikula@...ux.intel.com>
Cc:     Andrzej Hajda <a.hajda@...sung.com>,
        Emil Velikov <emil.l.velikov@...il.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "Sun, Jing A" <jing.a.sun@...el.com>,
        "Vetter, Daniel" <daniel.vetter@...el.com>,
        Thierry Reding <treding@...dia.com>
Subject: Re: [PATCH]"drm: change DRM_MIPI_DSI module type from "bool" to
 "tristate".

On Thu, Oct 20, 2016 at 04:44:49PM +0300, Jani Nikula wrote:
> On Thu, 20 Oct 2016, Andrzej Hajda <a.hajda@...sung.com> wrote:
> > Hi Jani,
> >
> > Forgive me late response.
> >
> > On 12.10.2016 16:28, Jani Nikula wrote:
> >> On Wed, 12 Oct 2016, Emil Velikov <emil.l.velikov@...il.com> wrote:
> >>> On 11 October 2016 at 10:33, Jani Nikula <jani.nikula@...ux.intel.com> wrote:
> >>>> On Tue, 11 Oct 2016, "Sun, Jing A" <jing.a.sun@...el.com> wrote:
> >>>>> It's needed that DRM Driver module could be removed and reloaded after
> >>>>> kernel booting on the projects that I have been working on, and I hope
> >>>>> such module type change could be accepted. Looks like Iwai has similar
> >>>>> change request as well. Would you please review it and let us know if
> >>>>> any concerns?
> >>>> Looking at the Kconfig, selecting CONFIG_DRM_MIPI_DSI is against the
> >>>> recommendations of Documentation/kbuild/kconfig-language.txt:
> >>>>
> >>>>         select should be used with care. select will force
> >>>>         a symbol to a value without visiting the dependencies.
> >>>>         By abusing select you are able to select a symbol FOO even
> >>>>         if FOO depends on BAR that is not set.
> >>>>         In general use select only for non-visible symbols
> >>>>         (no prompts anywhere) and for symbols with no dependencies.
> >>>>         That will limit the usefulness but on the other hand avoid
> >>>>         the illegal configurations all over.
> >>>>
> >>>> Indeed, you may end up with CONFIG_DRM_MIPI_DSI=y and CONFIG_DRM=m,
> >>>> which violates DRM_MIPI_DSI dependency on CONFIG_DRM. This is broken and
> >>>> should be fixed. The suggested patch does *not* fix this issue.
> >>>>
> >>> Jani, git log suggests you as the unfortunate author of the select
> >>> DRM_MIPI_DSI/select DRM_PANEL hunks in i915 ;-)
> >> /o\
> >>
> >> As much as my present self would like to scold my past self for all his
> >> mistakes, I have to remind myself that it is the mistakes that have
> >> given me invaluable experience that my past self didn't have. I can only
> >> hope my future self will have time to fix even a fraction of the
> >> mistakes.
> >>
> >> Anyway, as Andrzej pointed out, all configs that select DRM_MIPI_DSI
> >> also depend on DRM, so this problem can't currently occur. Once dsi bus
> >> un-registration gets addressed, we can turn DRM_MIPI_DSI into a tristate
> >> config (i.e. a loadable module).
> >
> > There is already patch adding bus unregistration [1]. It was published
> > together
> > with 'tristate' patch [2], both were created by Takashi few months ago.
> 
> Right. So make that "Once dis bus un-registration gets merged
> upstream". ;)

Someone volunteering for some review pls?
-Daniel

> 
> BR,
> Jani.
> 
> 
> >
> > [1]:
> > https://lists.freedesktop.org/archives/dri-devel/2016-August/114870.html
> > [2]:
> > https://lists.freedesktop.org/archives/dri-devel/2016-August/114497.html
> >
> > Regards
> > Andrzej
> >
> >>
> >> BR,
> >> Jani.
> >>
> >
> 
> -- 
> Jani Nikula, Intel Open Source Technology Center
> _______________________________________________
> dri-devel mailing list
> dri-devel@...ts.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch

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