drm/sun4i: link in front-end code if needed

Message ID 20180223131112.715992-1-arnd@arndb.de
State New
Headers show
Series
  • drm/sun4i: link in front-end code if needed
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Commit Message

Arnd Bergmann Feb. 23, 2018, 1:06 p.m.
When the base sun4i DRM driver is built-in but the back-end is
a loadable module, we run into a link error:

drivers/gpu/drm/sun4i/sun4i_drv.o: In function `sun4i_drv_probe':
sun4i_drv.c:(.text+0x60c): undefined reference to `sun4i_frontend_of_table'

The dependency is a bit tricky, the best workaround I have come up
with is to use a Makefile hack to to interpret both
CONFIG_DRM_SUN4I_BACKEND=m and CONFIG_DRM_SUN4I_BACKEND=y
as a directive to build the front-end the same way as the main module.

Fixes: dd0421f47505 ("drm/sun4i: Add a driver for the display frontend")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 drivers/gpu/drm/sun4i/Makefile | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

Comments

Maxime Ripard Feb. 26, 2018, 10:53 a.m. | #1
On Mon, Feb 26, 2018 at 10:31:51AM +0100, Arnd Bergmann wrote:
> On Mon, Feb 26, 2018 at 10:21 AM, Maxime Ripard

> <maxime.ripard@bootlin.com> wrote:

> > Hi,

> >

> > On Fri, Feb 23, 2018 at 02:06:52PM +0100, Arnd Bergmann wrote:

> >> When the base sun4i DRM driver is built-in but the back-end is

> >> a loadable module, we run into a link error:

> >>

> >> drivers/gpu/drm/sun4i/sun4i_drv.o: In function `sun4i_drv_probe':

> >> sun4i_drv.c:(.text+0x60c): undefined reference to `sun4i_frontend_of_table'

> >>

> >> The dependency is a bit tricky, the best workaround I have come up

> >> with is to use a Makefile hack to to interpret both

> >> CONFIG_DRM_SUN4I_BACKEND=m and CONFIG_DRM_SUN4I_BACKEND=y

> >> as a directive to build the front-end the same way as the main module.

> >>

> >> Fixes: dd0421f47505 ("drm/sun4i: Add a driver for the display frontend")

> >> Signed-off-by: Arnd Bergmann <arnd@arndb.de>

> >> ---

> >>  drivers/gpu/drm/sun4i/Makefile | 5 ++++-

> >>  1 file changed, 4 insertions(+), 1 deletion(-)

> >>

> >> diff --git a/drivers/gpu/drm/sun4i/Makefile b/drivers/gpu/drm/sun4i/Makefile

> >> index 582607c0c488..db14e023256b 100644

> >> --- a/drivers/gpu/drm/sun4i/Makefile

> >> +++ b/drivers/gpu/drm/sun4i/Makefile

> >> @@ -25,6 +25,9 @@ obj-$(CONFIG_DRM_SUN4I)             += sun4i-tcon.o

> >>  obj-$(CONFIG_DRM_SUN4I)              += sun4i_tv.o

> >>  obj-$(CONFIG_DRM_SUN4I)              += sun6i_drc.o

> >>

> >> -obj-$(CONFIG_DRM_SUN4I_BACKEND)      += sun4i-backend.o sun4i-frontend.o

> >> +obj-$(CONFIG_DRM_SUN4I_BACKEND)      += sun4i-backend.o

> >> +ifdef CONFIG_DRM_SUN4I_BACKEND

> >> +obj-$(CONFIG_DRM_SUN4I)              += sun4i-frontend.o

> >> +endif

> >

> > Can we just create a Kconfig symbol, selected by DRM_SUN4I_BACKEND,

> > and we would export the symbol?

> 

> Yes, I think that would work just as well. Something like

> 

> config DRM_SUN4I_FRONTEND

>       tristate

>       default DRM_SUN4I if CONFIG_DRM_SUN4I_BACKEND != n

> 

> should do the trick.


I had more something like this in mind:
https://pastebin.com/raw/XydvzAtz

Maxime

-- 
Maxime Ripard, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering
https://bootlin.com
Chen-Yu Tsai Feb. 26, 2018, 10:55 a.m. | #2
On Mon, Feb 26, 2018 at 6:53 PM, Maxime Ripard
<maxime.ripard@bootlin.com> wrote:
> On Mon, Feb 26, 2018 at 10:31:51AM +0100, Arnd Bergmann wrote:
>> On Mon, Feb 26, 2018 at 10:21 AM, Maxime Ripard
>> <maxime.ripard@bootlin.com> wrote:
>> > Hi,
>> >
>> > On Fri, Feb 23, 2018 at 02:06:52PM +0100, Arnd Bergmann wrote:
>> >> When the base sun4i DRM driver is built-in but the back-end is
>> >> a loadable module, we run into a link error:
>> >>
>> >> drivers/gpu/drm/sun4i/sun4i_drv.o: In function `sun4i_drv_probe':
>> >> sun4i_drv.c:(.text+0x60c): undefined reference to `sun4i_frontend_of_table'
>> >>
>> >> The dependency is a bit tricky, the best workaround I have come up
>> >> with is to use a Makefile hack to to interpret both
>> >> CONFIG_DRM_SUN4I_BACKEND=m and CONFIG_DRM_SUN4I_BACKEND=y
>> >> as a directive to build the front-end the same way as the main module.
>> >>
>> >> Fixes: dd0421f47505 ("drm/sun4i: Add a driver for the display frontend")
>> >> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
>> >> ---
>> >>  drivers/gpu/drm/sun4i/Makefile | 5 ++++-
>> >>  1 file changed, 4 insertions(+), 1 deletion(-)
>> >>
>> >> diff --git a/drivers/gpu/drm/sun4i/Makefile b/drivers/gpu/drm/sun4i/Makefile
>> >> index 582607c0c488..db14e023256b 100644
>> >> --- a/drivers/gpu/drm/sun4i/Makefile
>> >> +++ b/drivers/gpu/drm/sun4i/Makefile
>> >> @@ -25,6 +25,9 @@ obj-$(CONFIG_DRM_SUN4I)             += sun4i-tcon.o
>> >>  obj-$(CONFIG_DRM_SUN4I)              += sun4i_tv.o
>> >>  obj-$(CONFIG_DRM_SUN4I)              += sun6i_drc.o
>> >>
>> >> -obj-$(CONFIG_DRM_SUN4I_BACKEND)      += sun4i-backend.o sun4i-frontend.o
>> >> +obj-$(CONFIG_DRM_SUN4I_BACKEND)      += sun4i-backend.o
>> >> +ifdef CONFIG_DRM_SUN4I_BACKEND
>> >> +obj-$(CONFIG_DRM_SUN4I)              += sun4i-frontend.o
>> >> +endif
>> >
>> > Can we just create a Kconfig symbol, selected by DRM_SUN4I_BACKEND,
>> > and we would export the symbol?
>>
>> Yes, I think that would work just as well. Something like
>>
>> config DRM_SUN4I_FRONTEND
>>       tristate
>>       default DRM_SUN4I if CONFIG_DRM_SUN4I_BACKEND != n
>>
>> should do the trick.
>
> I had more something like this in mind:
> https://pastebin.com/raw/XydvzAtz

This doesn't solve the issue at hand, which is sun4i-drv (CONFIG_DRM_SUN4I)
requires something in sun4i-backend (CONFIG_DRM_SUN4I_BACKEND), and if
sun4i-drv is built-in, then anything it uses must also be built-in.

ChenYu

Patch

diff --git a/drivers/gpu/drm/sun4i/Makefile b/drivers/gpu/drm/sun4i/Makefile
index 582607c0c488..db14e023256b 100644
--- a/drivers/gpu/drm/sun4i/Makefile
+++ b/drivers/gpu/drm/sun4i/Makefile
@@ -25,6 +25,9 @@  obj-$(CONFIG_DRM_SUN4I)		+= sun4i-tcon.o
 obj-$(CONFIG_DRM_SUN4I)		+= sun4i_tv.o
 obj-$(CONFIG_DRM_SUN4I)		+= sun6i_drc.o
 
-obj-$(CONFIG_DRM_SUN4I_BACKEND)	+= sun4i-backend.o sun4i-frontend.o
+obj-$(CONFIG_DRM_SUN4I_BACKEND)	+= sun4i-backend.o
+ifdef CONFIG_DRM_SUN4I_BACKEND
+obj-$(CONFIG_DRM_SUN4I)		+= sun4i-frontend.o
+endif
 obj-$(CONFIG_DRM_SUN4I_HDMI)	+= sun4i-drm-hdmi.o
 obj-$(CONFIG_DRM_SUN8I_MIXER)	+= sun8i-mixer.o