linux-kernel - Re: [PATCH]"drm: change DRM_MIPI_DSI module type from "bool" to "tristate".

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Message-ID: <CACvgo53Q0_G-9KHaTFX=0NskFYnf9vOrV8arTw0gVqnZ8Jrm6w@mail.gmail.com>
Date:   Wed, 12 Oct 2016 12:28:40 +0100
From:   Emil Velikov <emil.l.velikov@...il.com>
To:     Jani Nikula <jani.nikula@...ux.intel.com>
Cc:     "Sun, Jing A" <jing.a.sun@...el.com>, Takashi Iwai <tiwai@...e.de>,
        "airlied@...ux.ie" <airlied@...ux.ie>,
        "Vetter, Daniel" <daniel.vetter@...el.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "a.hajda@...sung.com" <a.hajda@...sung.com>,
        Thierry Reding <treding@...dia.com>
Subject: Re: [PATCH]"drm: change DRM_MIPI_DSI module type from "bool" to "tristate".

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 ;-)

>From a cutesy skim through panel/ there are a handful of things to
squash - unused select/depend on, s/select/depend on/ etc. Sadly I
don't have the time to address these :-\

Regards,
Emil