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[PATCH]"drm: change DRM_MIPI_DSI module type from "bool" to "tristate".

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  [PATCH]"drm: change DRM_MIPI_DSI module type from "bool" to  "tristate". "Sun, Jing A" <jing.a.sun@intel.com> - 2016-10-10 09:40 +0200
    Re: [PATCH]"drm: change DRM_MIPI_DSI module type from "bool" to "tristate". Jani Nikula <jani.nikula@linux.intel.com> - 2016-10-10 10:30 +0200
      Re: [PATCH]"drm: change DRM_MIPI_DSI module type from "bool" to "tristate". Takashi Iwai <tiwai@suse.de> - 2016-10-10 12:00 +0200
        RE: [PATCH]"drm: change DRM_MIPI_DSI module type from "bool" to  "tristate". "Sun, Jing A" <jing.a.sun@intel.com> - 2016-10-11 10:50 +0200
          Re:  [PATCH]"drm: change DRM_MIPI_DSI module type from "bool" to "tristate". Andrzej Hajda <a.hajda@samsung.com> - 2016-10-11 11:20 +0200
          RE: [PATCH]"drm: change DRM_MIPI_DSI module type from "bool" to "tristate". Jani Nikula <jani.nikula@linux.intel.com> - 2016-10-11 11:40 +0200
            Re:  [PATCH]"drm: change DRM_MIPI_DSI module type from "bool" to "tristate". Andrzej Hajda <a.hajda@samsung.com> - 2016-10-11 12:00 +0200
              RE: [PATCH]"drm: change DRM_MIPI_DSI module type from "bool" to  "tristate". "Sun, Jing A" <jing.a.sun@intel.com> - 2016-10-12 05:10 +0200
                Re: [PATCH]"drm: change DRM_MIPI_DSI module type from "bool" to  "tristate". Daniel Vetter <daniel@ffwll.ch> - 2016-10-12 09:00 +0200
                  RE: [PATCH]"drm: change DRM_MIPI_DSI module type from "bool" to  "tristate". "Sun, Jing A" <jing.a.sun@intel.com> - 2016-10-12 11:10 +0200
                    RE: [PATCH]"drm: change DRM_MIPI_DSI module type from "bool" to "tristate". Jani Nikula <jani.nikula@linux.intel.com> - 2016-10-12 13:00 +0200
            Re: [PATCH]"drm: change DRM_MIPI_DSI module type from "bool" to "tristate". Emil Velikov <emil.l.velikov@gmail.com> - 2016-10-12 13:30 +0200
              Re: [PATCH]"drm: change DRM_MIPI_DSI module type from "bool" to "tristate". Jani Nikula <jani.nikula@linux.intel.com> - 2016-10-12 16:30 +0200

#1498151 — [PATCH]"drm: change DRM_MIPI_DSI module type from "bool" to "tristate".

Dear Maintainers,

Please kindly review my patch as below. It's based on the mainline branch.

From b401009f79883ac5e9d41525c9d54b800ece2e22 Mon Sep 17 00:00:00 2001
From: Jing SUN <jing.a.sun@intel.com>
Date: Mon, 10 Oct 2016 14:06:54 +0800
Subject: [PATCH 1/1] drm: change DRM_MIPI_DSI module type from "bool" to
 "tristate".

A lot of drm driver modules, which are designed
to be loadable, select DRM_MIPI_DSI, while that
being "bool" prevents those from getting reloaded.

Signed-off-by: Jing SUN <jing.a.sun@intel.com>
---
 drivers/gpu/drm/Kconfig | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
index fc35731..67668a0 100644
--- a/drivers/gpu/drm/Kconfig
+++ b/drivers/gpu/drm/Kconfig
@@ -22,7 +22,7 @@ menuconfig DRM
 	  (/dev/agpgart) support if it is available for your platform.
 
 config DRM_MIPI_DSI
-	bool
+	tristate
 	depends on DRM
 
 config DRM_DP_AUX_CHARDEV
-- 
2.7.4

Regards,
Sun, Jing

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#1498161 — Re: [PATCH]"drm: change DRM_MIPI_DSI module type from "bool" to "tristate".

On Mon, 10 Oct 2016, "Sun, Jing A" <jing.a.sun@intel.com> wrote:
> Dear Maintainers,
>
> Please kindly review my patch as below. It's based on the mainline branch.
>
> From b401009f79883ac5e9d41525c9d54b800ece2e22 Mon Sep 17 00:00:00 2001
> From: Jing SUN <jing.a.sun@intel.com>
> Date: Mon, 10 Oct 2016 14:06:54 +0800
> Subject: [PATCH 1/1] drm: change DRM_MIPI_DSI module type from "bool" to
>  "tristate".
>
> A lot of drm driver modules, which are designed
> to be loadable, select DRM_MIPI_DSI, while that
> being "bool" prevents those from getting reloaded.

You're missing some lists and people from distribution, added now.

See the discussion starting at [1]. I don't know if anything has
happened since then. Takashi?

BR,
Jani.


[1] http://lkml.kernel.org/r/s5hh9bhvj7j.wl-tiwai@suse.de


>
> Signed-off-by: Jing SUN <jing.a.sun@intel.com>
> ---
>  drivers/gpu/drm/Kconfig | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
> index fc35731..67668a0 100644
> --- a/drivers/gpu/drm/Kconfig
> +++ b/drivers/gpu/drm/Kconfig
> @@ -22,7 +22,7 @@ menuconfig DRM
>  	  (/dev/agpgart) support if it is available for your platform.
>  
>  config DRM_MIPI_DSI
> -	bool
> +	tristate
>  	depends on DRM
>  
>  config DRM_DP_AUX_CHARDEV

-- 
Jani Nikula, Intel Open Source Technology Center

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#1498203 — Re: [PATCH]"drm: change DRM_MIPI_DSI module type from "bool" to "tristate".

On Mon, 10 Oct 2016 10:28:31 +0200,
Jani Nikula wrote:
> 
> On Mon, 10 Oct 2016, "Sun, Jing A" <jing.a.sun@intel.com> wrote:
> > Dear Maintainers,
> >
> > Please kindly review my patch as below. It's based on the mainline branch.
> >
> > From b401009f79883ac5e9d41525c9d54b800ece2e22 Mon Sep 17 00:00:00 2001
> > From: Jing SUN <jing.a.sun@intel.com>
> > Date: Mon, 10 Oct 2016 14:06:54 +0800
> > Subject: [PATCH 1/1] drm: change DRM_MIPI_DSI module type from "bool" to
> >  "tristate".
> >
> > A lot of drm driver modules, which are designed
> > to be loadable, select DRM_MIPI_DSI, while that
> > being "bool" prevents those from getting reloaded.
> 
> You're missing some lists and people from distribution, added now.
> 
> See the discussion starting at [1]. I don't know if anything has
> happened since then. Takashi?

Unfortunately, nothing seems to have happened since my last patch due
to little interest.  I'd be glad if the patch is revived.

(BTW, I'm traveling in these two weeks, so the further reply will be
 delayed.)


thanks,

Takashi


> 
> BR,
> Jani.
> 
> 
> [1] http://lkml.kernel.org/r/s5hh9bhvj7j.wl-tiwai@suse.de
> 
> 
> >
> > Signed-off-by: Jing SUN <jing.a.sun@intel.com>
> > ---
> >  drivers/gpu/drm/Kconfig | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
> > index fc35731..67668a0 100644
> > --- a/drivers/gpu/drm/Kconfig
> > +++ b/drivers/gpu/drm/Kconfig
> > @@ -22,7 +22,7 @@ menuconfig DRM
> >  	  (/dev/agpgart) support if it is available for your platform.
> >  
> >  config DRM_MIPI_DSI
> > -	bool
> > +	tristate
> >  	depends on DRM
> >  
> >  config DRM_DP_AUX_CHARDEV
> 
> -- 
> Jani Nikula, Intel Open Source Technology Center
> 

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#1498661

Dear Maintainers,

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?

Regards,
Sun, Jing


-----Original Message-----
From: Takashi Iwai [mailto:tiwai@suse.de] 
Sent: Monday, October 10, 2016 5:57 PM
To: Jani Nikula
Cc: Sun, Jing A; airlied@linux.ie; Vetter, Daniel; linux-kernel@vger.kernel.org; dri-devel@lists.freedesktop.org; Takashi Iwai; a.hajda@samsung.com; Thierry Reding
Subject: Re: [PATCH]"drm: change DRM_MIPI_DSI module type from "bool" to "tristate".

On Mon, 10 Oct 2016 10:28:31 +0200,
Jani Nikula wrote:
> 
> On Mon, 10 Oct 2016, "Sun, Jing A" <jing.a.sun@intel.com> wrote:
> > Dear Maintainers,
> >
> > Please kindly review my patch as below. It's based on the mainline branch.
> >
> > From b401009f79883ac5e9d41525c9d54b800ece2e22 Mon Sep 17 00:00:00 
> > 2001
> > From: Jing SUN <jing.a.sun@intel.com>
> > Date: Mon, 10 Oct 2016 14:06:54 +0800
> > Subject: [PATCH 1/1] drm: change DRM_MIPI_DSI module type from 
> > "bool" to  "tristate".
> >
> > A lot of drm driver modules, which are designed to be loadable, 
> > select DRM_MIPI_DSI, while that being "bool" prevents those from 
> > getting reloaded.
> 
> You're missing some lists and people from distribution, added now.
> 
> See the discussion starting at [1]. I don't know if anything has 
> happened since then. Takashi?

Unfortunately, nothing seems to have happened since my last patch due to little interest.  I'd be glad if the patch is revived.

(BTW, I'm traveling in these two weeks, so the further reply will be
 delayed.)


thanks,

Takashi


> 
> BR,
> Jani.
> 
> 
> [1] http://lkml.kernel.org/r/s5hh9bhvj7j.wl-tiwai@suse.de
> 
> 
> >
> > Signed-off-by: Jing SUN <jing.a.sun@intel.com>
> > ---
> >  drivers/gpu/drm/Kconfig | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig index 
> > fc35731..67668a0 100644
> > --- a/drivers/gpu/drm/Kconfig
> > +++ b/drivers/gpu/drm/Kconfig
> > @@ -22,7 +22,7 @@ menuconfig DRM
> >  	  (/dev/agpgart) support if it is available for your platform.
> >  
> >  config DRM_MIPI_DSI
> > -	bool
> > +	tristate
> >  	depends on DRM
> >  
> >  config DRM_DP_AUX_CHARDEV
> 
> --
> Jani Nikula, Intel Open Source Technology Center
> 

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#1498673 — Re: [PATCH]"drm: change DRM_MIPI_DSI module type from "bool" to "tristate".

Hi,

This patch misses dsi bus un-registration.
However I have reviewed two patches of Takashi which solves
the same issue more completely [1]. These patches were not
accepted neither.

[1]:
https://lists.freedesktop.org/archives/dri-devel/2016-August/114870.html

Regards
Andrzej

On 11.10.2016 10:40, Sun, Jing A wrote:
> Dear Maintainers,
>
> 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?
>
> Regards,
> Sun, Jing
>
>
> -----Original Message-----
> From: Takashi Iwai [mailto:tiwai@suse.de] 
> Sent: Monday, October 10, 2016 5:57 PM
> To: Jani Nikula
> Cc: Sun, Jing A; airlied@linux.ie; Vetter, Daniel; linux-kernel@vger.kernel.org; dri-devel@lists.freedesktop.org; Takashi Iwai; a.hajda@samsung.com; Thierry Reding
> Subject: Re: [PATCH]"drm: change DRM_MIPI_DSI module type from "bool" to "tristate".
>
> On Mon, 10 Oct 2016 10:28:31 +0200,
> Jani Nikula wrote:
>> On Mon, 10 Oct 2016, "Sun, Jing A" <jing.a.sun@intel.com> wrote:
>>> Dear Maintainers,
>>>
>>> Please kindly review my patch as below. It's based on the mainline branch.
>>>
>>> From b401009f79883ac5e9d41525c9d54b800ece2e22 Mon Sep 17 00:00:00 
>>> 2001
>>> From: Jing SUN <jing.a.sun@intel.com>
>>> Date: Mon, 10 Oct 2016 14:06:54 +0800
>>> Subject: [PATCH 1/1] drm: change DRM_MIPI_DSI module type from 
>>> "bool" to  "tristate".
>>>
>>> A lot of drm driver modules, which are designed to be loadable, 
>>> select DRM_MIPI_DSI, while that being "bool" prevents those from 
>>> getting reloaded.
>> You're missing some lists and people from distribution, added now.
>>
>> See the discussion starting at [1]. I don't know if anything has 
>> happened since then. Takashi?
> Unfortunately, nothing seems to have happened since my last patch due to little interest.  I'd be glad if the patch is revived.
>
> (BTW, I'm traveling in these two weeks, so the further reply will be
>  delayed.)
>
>
> thanks,
>
> Takashi
>
>
>> BR,
>> Jani.
>>
>>
>> [1] http://lkml.kernel.org/r/s5hh9bhvj7j.wl-tiwai@suse.de
>>
>>
>>> Signed-off-by: Jing SUN <jing.a.sun@intel.com>
>>> ---
>>>  drivers/gpu/drm/Kconfig | 2 +-
>>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig index 
>>> fc35731..67668a0 100644
>>> --- a/drivers/gpu/drm/Kconfig
>>> +++ b/drivers/gpu/drm/Kconfig
>>> @@ -22,7 +22,7 @@ menuconfig DRM
>>>  	  (/dev/agpgart) support if it is available for your platform.
>>>  
>>>  config DRM_MIPI_DSI
>>> -	bool
>>> +	tristate
>>>  	depends on DRM
>>>  
>>>  config DRM_DP_AUX_CHARDEV
>> --
>> Jani Nikula, Intel Open Source Technology Center
>>
>
>

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#1498690 — RE: [PATCH]"drm: change DRM_MIPI_DSI module type from "bool" to "tristate".

On Tue, 11 Oct 2016, "Sun, Jing A" <jing.a.sun@intel.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.

Interestingly, I am able to reload i915 and drm. Our CI has tests for
i915 unload/reload, but does not check drm. In any case the config
problem should not impact the reloadability of i915.

BR,
Jani.

-- 
Jani Nikula, Intel Open Source Technology Center

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#1498696 — Re: [PATCH]"drm: change DRM_MIPI_DSI module type from "bool" to "tristate".

On 11.10.2016 11:33, Jani Nikula wrote:
> On Tue, 11 Oct 2016, "Sun, Jing A" <jing.a.sun@intel.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.

All existing drivers which selects DRM_MIPI_DSI also depends on DRM.
So the dependency is always true. I am not sure if it could not change in
the future, but in such case mipi_dsi bus should be completely detached from
DRM framework, I hope we have not such case yet :)

>
> 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.

At the moment it should not be possible.

Regards
Andrzej

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#1499332

Interestingly, I am able to reload i915 and drm. Our CI has tests for
i915 unload/reload, but does not check drm. In any case the config problem should not impact the reloadability of i915.
======
Sorry that I didn't make myself clear. In order to replace the default i915 module with an updated one, the related DRM modules also need to be updated to match the updated i915, hence the restriction.

Regards,
Sun, Jing


-----Original Message-----
From: Andrzej Hajda [mailto:a.hajda@samsung.com] 
Sent: Tuesday, October 11, 2016 5:53 PM
To: Jani Nikula; Sun, Jing A; Takashi Iwai
Cc: airlied@linux.ie; Vetter, Daniel; linux-kernel@vger.kernel.org; dri-devel@lists.freedesktop.org; Thierry Reding; Emil Velikov
Subject: Re: [PATCH]"drm: change DRM_MIPI_DSI module type from "bool" to "tristate".

On 11.10.2016 11:33, Jani Nikula wrote:
> On Tue, 11 Oct 2016, "Sun, Jing A" <jing.a.sun@intel.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.

All existing drivers which selects DRM_MIPI_DSI also depends on DRM.
So the dependency is always true. I am not sure if it could not change in the future, but in such case mipi_dsi bus should be completely detached from DRM framework, I hope we have not such case yet :)

>
> 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.

At the moment it should not be possible.

Regards
Andrzej

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#1499376

On Wed, Oct 12, 2016 at 03:08:24AM +0000, Sun, Jing A wrote:
> Interestingly, I am able to reload i915 and drm. Our CI has tests for
> i915 unload/reload, but does not check drm. In any case the config
> problem should not impact the reloadability of i915.
> ======
> Sorry that I didn't make myself clear. In order to replace the default
> i915 module with an updated one, the related DRM modules also need to be
> updated to match the updated i915, hence the restriction.

Just to avoid tears in the future: If you plan to ship this in product,
you won't ship.

And for debugging, just install a kernel with your changes for both drm
and i915.

In short, your use-case isn't really valid (but we could still make the
dsi code modular if people feel like).
-Daniel

> 
> Regards,
> Sun, Jing
> 
> 
> -----Original Message-----
> From: Andrzej Hajda [mailto:a.hajda@samsung.com] 
> Sent: Tuesday, October 11, 2016 5:53 PM
> To: Jani Nikula; Sun, Jing A; Takashi Iwai
> Cc: airlied@linux.ie; Vetter, Daniel; linux-kernel@vger.kernel.org; dri-devel@lists.freedesktop.org; Thierry Reding; Emil Velikov
> Subject: Re: [PATCH]"drm: change DRM_MIPI_DSI module type from "bool" to "tristate".
> 
> On 11.10.2016 11:33, Jani Nikula wrote:
> > On Tue, 11 Oct 2016, "Sun, Jing A" <jing.a.sun@intel.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.
> 
> All existing drivers which selects DRM_MIPI_DSI also depends on DRM.
> So the dependency is always true. I am not sure if it could not change in the future, but in such case mipi_dsi bus should be completely detached from DRM framework, I hope we have not such case yet :)
> 
> >
> > 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.
> 
> At the moment it should not be possible.
> 
> Regards
> Andrzej
> 
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel

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

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#1499439

I think "installing a kernel with my changes for both drm and i915" takes more time and effort to complete than "only updating DRM/i915 modules without rebuilding the whole kernel". In some cases, that's beneficial.

Also reloadablility is always a good thing to have and I truly hope Hajda/Iwai's patches would be accepted and merged.
No downside of it after all.

Regards,
Sun, Jing

-----Original Message-----
From: Daniel Vetter [mailto:daniel.vetter@ffwll.ch] On Behalf Of Daniel Vetter
Sent: Wednesday, October 12, 2016 2:52 PM
To: Sun, Jing A
Cc: Andrzej Hajda; Jani Nikula; Takashi Iwai; Emil Velikov; linux-kernel@vger.kernel.org; dri-devel@lists.freedesktop.org; Vetter, Daniel; Thierry Reding
Subject: Re: [PATCH]"drm: change DRM_MIPI_DSI module type from "bool" to "tristate".

On Wed, Oct 12, 2016 at 03:08:24AM +0000, Sun, Jing A wrote:
> Interestingly, I am able to reload i915 and drm. Our CI has tests for
> i915 unload/reload, but does not check drm. In any case the config 
> problem should not impact the reloadability of i915.
> ======
> Sorry that I didn't make myself clear. In order to replace the default
> i915 module with an updated one, the related DRM modules also need to 
> be updated to match the updated i915, hence the restriction.

Just to avoid tears in the future: If you plan to ship this in product, you won't ship.

And for debugging, just install a kernel with your changes for both drm and i915.

In short, your use-case isn't really valid (but we could still make the dsi code modular if people feel like).
-Daniel

> 
> Regards,
> Sun, Jing
> 
> 
> -----Original Message-----
> From: Andrzej Hajda [mailto:a.hajda@samsung.com]
> Sent: Tuesday, October 11, 2016 5:53 PM
> To: Jani Nikula; Sun, Jing A; Takashi Iwai
> Cc: airlied@linux.ie; Vetter, Daniel; linux-kernel@vger.kernel.org; 
> dri-devel@lists.freedesktop.org; Thierry Reding; Emil Velikov
> Subject: Re: [PATCH]"drm: change DRM_MIPI_DSI module type from "bool" to "tristate".
> 
> On 11.10.2016 11:33, Jani Nikula wrote:
> > On Tue, 11 Oct 2016, "Sun, Jing A" <jing.a.sun@intel.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.
> 
> All existing drivers which selects DRM_MIPI_DSI also depends on DRM.
> So the dependency is always true. I am not sure if it could not change 
> in the future, but in such case mipi_dsi bus should be completely 
> detached from DRM framework, I hope we have not such case yet :)
> 
> >
> > 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.
> 
> At the moment it should not be possible.
> 
> Regards
> Andrzej
> 
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel

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

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#1499481 — RE: [PATCH]"drm: change DRM_MIPI_DSI module type from "bool" to "tristate".

On Wed, 12 Oct 2016, "Sun, Jing A" <jing.a.sun@intel.com> wrote:
> I think "installing a kernel with my changes for both drm and i915"
> takes more time and effort to complete than "only updating DRM/i915
> modules without rebuilding the whole kernel". In some cases, that's
> beneficial.

It's possible to change and rebuild and update just the drm and i915,
but you need to be careful to build against the same tree as the ones
you are replacing. This is like using out-of-tree modules (which is
something I can't recommend no matter what, but that's another
discussion).

However, this is completely different from planning to update drm and
i915 modules on a running production system by unloading the old ones
and probing the new ones. Don't do that. It will be a disaster.

> Also reloadablility is always a good thing to have and I truly hope
> Hajda/Iwai's patches would be accepted and merged.  No downside of it
> after all.

I think it's good to be able to unload and reload modules for debugging
and development, but not for normal use.

BR,
Jani.


-- 
Jani Nikula, Intel Open Source Technology Center

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#1499492 — Re: [PATCH]"drm: change DRM_MIPI_DSI module type from "bool" to "tristate".

On 11 October 2016 at 10:33, Jani Nikula <jani.nikula@linux.intel.com> wrote:
> On Tue, 11 Oct 2016, "Sun, Jing A" <jing.a.sun@intel.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

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#1499720 — Re: [PATCH]"drm: change DRM_MIPI_DSI module type from "bool" to "tristate".

On Wed, 12 Oct 2016, Emil Velikov <emil.l.velikov@gmail.com> wrote:
> On 11 October 2016 at 10:33, Jani Nikula <jani.nikula@linux.intel.com> wrote:
>> On Tue, 11 Oct 2016, "Sun, Jing A" <jing.a.sun@intel.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).

BR,
Jani.

-- 
Jani Nikula, Intel Open Source Technology Center

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