[PATCH v1 1/1] drm/drm_panel: Fix EXPORT of drm_panel_of_backlight() one more time

[PATCH v1 1/1] drm/drm_panel: Fix EXPORT of drm_panel_of_backlight() one more time

[Andy Shevchenko]

The initial commit followed by the fix didn't take into consideration the case

CONFIG_DRM_PANEL=y
CONFIG_BACKLIGHT_CLASS_DEVICE=m
CONFIG_DRM_I915=y

where symbol devm_of_find_backlight() is not reachable from DRM subsystem.
Quick fix is to avoid drm_panel_of_backlight() from exporting in such case.

Fixes: 907aa265fde6 ("drm/drm_panel: fix EXPORT of drm_panel_of_backlight")
Reported-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Thierry Reding <thierry.reding@gmail.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Sean Paul <sean@poorly.run>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: dri-devel@lists.freedesktop.org
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
---
 drivers/gpu/drm/drm_panel.c | 2 +-
 include/drm/drm_panel.h     | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/drm_panel.c b/drivers/gpu/drm/drm_panel.c
index 79ff3fdf6f6e..8c7bac85a793 100644
--- a/drivers/gpu/drm/drm_panel.c
+++ b/drivers/gpu/drm/drm_panel.c
@@ -302,7 +302,7 @@ struct drm_panel *of_drm_find_panel(const struct device_node *np)
 EXPORT_SYMBOL(of_drm_find_panel);
 #endif
 
-#if IS_ENABLED(CONFIG_BACKLIGHT_CLASS_DEVICE)
+#if IS_REACHABLE(CONFIG_BACKLIGHT_CLASS_DEVICE)
 /**
  * drm_panel_of_backlight - use backlight device node for backlight
  * @panel: DRM panel
diff --git a/include/drm/drm_panel.h b/include/drm/drm_panel.h
index 5f27b693e1a0..121f7aabccd1 100644
--- a/include/drm/drm_panel.h
+++ b/include/drm/drm_panel.h
@@ -198,7 +198,7 @@ static inline struct drm_panel *of_drm_find_panel(const struct device_node *np)
 }
 #endif
 
-#if IS_ENABLED(CONFIG_BACKLIGHT_CLASS_DEVICE)
+#if IS_REACHABLE(CONFIG_BACKLIGHT_CLASS_DEVICE)
 int drm_panel_of_backlight(struct drm_panel *panel);
 #else
 static inline int drm_panel_of_backlight(struct drm_panel *panel)
-- 
2.24.0

Re: [PATCH v1 1/1] drm/drm_panel: Fix EXPORT of drm_panel_of_backlight() one more time

[Randy Dunlap]

On 12/17/19 6:07 AM, Andy Shevchenko wrote:
> The initial commit followed by the fix didn't take into consideration the case
> 
> CONFIG_DRM_PANEL=y
> CONFIG_BACKLIGHT_CLASS_DEVICE=m
> CONFIG_DRM_I915=y
> 
> where symbol devm_of_find_backlight() is not reachable from DRM subsystem.
> Quick fix is to avoid drm_panel_of_backlight() from exporting in such case.
> 
> Fixes: 907aa265fde6 ("drm/drm_panel: fix EXPORT of drm_panel_of_backlight")
> Reported-by: Randy Dunlap <rdunlap@infradead.org>
> Cc: Linus Walleij <linus.walleij@linaro.org>
> Cc: Sam Ravnborg <sam@ravnborg.org>
> Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> Cc: Thierry Reding <thierry.reding@gmail.com>
> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> Cc: Sean Paul <sean@poorly.run>
> Cc: David Airlie <airlied@linux.ie>
> Cc: Daniel Vetter <daniel@ffwll.ch>
> Cc: Maxime Ripard <mripard@kernel.org>
> Cc: dri-devel@lists.freedesktop.org
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

Yes, that fixes the build error.  Thanks.

Acked-by: Randy Dunlap <rdunlap@infradead.org> # build-tested


> ---
>  drivers/gpu/drm/drm_panel.c | 2 +-
>  include/drm/drm_panel.h     | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_panel.c b/drivers/gpu/drm/drm_panel.c
> index 79ff3fdf6f6e..8c7bac85a793 100644
> --- a/drivers/gpu/drm/drm_panel.c
> +++ b/drivers/gpu/drm/drm_panel.c
> @@ -302,7 +302,7 @@ struct drm_panel *of_drm_find_panel(const struct device_node *np)
>  EXPORT_SYMBOL(of_drm_find_panel);
>  #endif
>  
> -#if IS_ENABLED(CONFIG_BACKLIGHT_CLASS_DEVICE)
> +#if IS_REACHABLE(CONFIG_BACKLIGHT_CLASS_DEVICE)
>  /**
>   * drm_panel_of_backlight - use backlight device node for backlight
>   * @panel: DRM panel
> diff --git a/include/drm/drm_panel.h b/include/drm/drm_panel.h
> index 5f27b693e1a0..121f7aabccd1 100644
> --- a/include/drm/drm_panel.h
> +++ b/include/drm/drm_panel.h
> @@ -198,7 +198,7 @@ static inline struct drm_panel *of_drm_find_panel(const struct device_node *np)
>  }
>  #endif
>  
> -#if IS_ENABLED(CONFIG_BACKLIGHT_CLASS_DEVICE)
> +#if IS_REACHABLE(CONFIG_BACKLIGHT_CLASS_DEVICE)
>  int drm_panel_of_backlight(struct drm_panel *panel);
>  #else
>  static inline int drm_panel_of_backlight(struct drm_panel *panel)
> 


-- 
~Randy

Re: [PATCH v1 1/1] drm/drm_panel: Fix EXPORT of drm_panel_of_backlight() one more time

[Sam Ravnborg]

On Tue, Dec 17, 2019 at 08:25:03AM -0800, Randy Dunlap wrote:
> On 12/17/19 6:07 AM, Andy Shevchenko wrote:
> > The initial commit followed by the fix didn't take into consideration the case
> > 
> > CONFIG_DRM_PANEL=y
> > CONFIG_BACKLIGHT_CLASS_DEVICE=m
> > CONFIG_DRM_I915=y
> > 
> > where symbol devm_of_find_backlight() is not reachable from DRM subsystem.
> > Quick fix is to avoid drm_panel_of_backlight() from exporting in such case.
> > 
> > Fixes: 907aa265fde6 ("drm/drm_panel: fix EXPORT of drm_panel_of_backlight")
> > Reported-by: Randy Dunlap <rdunlap@infradead.org>
> > Cc: Linus Walleij <linus.walleij@linaro.org>
> > Cc: Sam Ravnborg <sam@ravnborg.org>
> > Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> > Cc: Thierry Reding <thierry.reding@gmail.com>
> > Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> > Cc: Sean Paul <sean@poorly.run>
> > Cc: David Airlie <airlied@linux.ie>
> > Cc: Daniel Vetter <daniel@ffwll.ch>
> > Cc: Maxime Ripard <mripard@kernel.org>
> > Cc: dri-devel@lists.freedesktop.org
> > Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> 
> Yes, that fixes the build error.  Thanks.
> 
> Acked-by: Randy Dunlap <rdunlap@infradead.org> # build-tested

Hi Andy - thanks for fixing this. And thanks Randy for verifying the
fix.
It passed my build test and is now pushed to drm-misc-next.

	Sam

Re: [PATCH v1 1/1] drm/drm_panel: Fix EXPORT of drm_panel_of_backlight() one more time

[Jani Nikula]

On Tue, 17 Dec 2019, Sam Ravnborg <sam@ravnborg.org> wrote:
> On Tue, Dec 17, 2019 at 08:25:03AM -0800, Randy Dunlap wrote:
>> On 12/17/19 6:07 AM, Andy Shevchenko wrote:
>> > The initial commit followed by the fix didn't take into consideration the case
>> > 
>> > CONFIG_DRM_PANEL=y
>> > CONFIG_BACKLIGHT_CLASS_DEVICE=m
>> > CONFIG_DRM_I915=y
>> > 
>> > where symbol devm_of_find_backlight() is not reachable from DRM subsystem.
>> > Quick fix is to avoid drm_panel_of_backlight() from exporting in such case.
>> > 
>> > Fixes: 907aa265fde6 ("drm/drm_panel: fix EXPORT of drm_panel_of_backlight")
>> > Reported-by: Randy Dunlap <rdunlap@infradead.org>
>> > Cc: Linus Walleij <linus.walleij@linaro.org>
>> > Cc: Sam Ravnborg <sam@ravnborg.org>
>> > Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
>> > Cc: Thierry Reding <thierry.reding@gmail.com>
>> > Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
>> > Cc: Sean Paul <sean@poorly.run>
>> > Cc: David Airlie <airlied@linux.ie>
>> > Cc: Daniel Vetter <daniel@ffwll.ch>
>> > Cc: Maxime Ripard <mripard@kernel.org>
>> > Cc: dri-devel@lists.freedesktop.org
>> > Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
>> 
>> Yes, that fixes the build error.  Thanks.
>> 
>> Acked-by: Randy Dunlap <rdunlap@infradead.org> # build-tested
>
> Hi Andy - thanks for fixing this. And thanks Randy for verifying the
> fix.
> It passed my build test and is now pushed to drm-misc-next.

As I wrote in [1], this allows a configuration that builds and links,
but is silently broken. You won't get backlight support in drm panel
which would be a reasonable expectation with
CONFIG_BACKLIGHT_CLASS_DEVICE=m.

BR,
Jani.


[1] http://mid.mail-archive.com/87d0cnynst.fsf@intel.com

-- 
Jani Nikula, Intel Open Source Graphics Center

Re: [PATCH v1 1/1] drm/drm_panel: Fix EXPORT of drm_panel_of_backlight() one more time

[Sam Ravnborg]

Hi Jani.

> As I wrote in [1], this allows a configuration that builds and links,
> but is silently broken. You won't get backlight support in drm panel
> which would be a reasonable expectation with
> CONFIG_BACKLIGHT_CLASS_DEVICE=m.

Agreed - it needs to be improved. But right now we had to fix the build
breakage.

http://lore.kernel.org/r/1413580403-16225-1-git-send-email-jani.nikula@intel.com
is added to my TODO list.
May take a stamp on this over xmas.

	Sam