linux-kernel - Re: [PATCH v2 -next] drm/vc4: Fix build error when CONFIG_DRM_VC4=y && CONFIG_RASPBERRYPI

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Date:   Wed, 6 Apr 2022 12:06:12 +0200
From:   Maxime Ripard <maxime@...no.tech>
To:     "Zhengbin (OSKernel)" <zhengbin13@...wei.com>
Cc:     emma@...olt.net, airlied@...ux.ie, daniel@...ll.ch,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        tangyizhou@...wei.com
Subject: Re: [PATCH v2 -next] drm/vc4: Fix build error when CONFIG_DRM_VC4=y
 && CONFIG_RASPBERRYPI_FIRMWARE=m

Hi,

On Mon, Mar 28, 2022 at 10:22:11AM +0800, Zhengbin (OSKernel) wrote:
> On 2022/3/25 21:05, Maxime Ripard wrote:
> > On Fri, Mar 25, 2022 at 10:18:31AM +0800, Zheng Bin wrote:
> > > If CONFIG_DRM_VC4=y, CONFIG_RASPBERRYPI_FIRMWARE=m, CONFIG_COMPILE_TEST=n,
> > > bulding fails:
> > > 
> > > drivers/gpu/drm/vc4/vc4_drv.o: In function `vc4_drm_bind':
> > > vc4_drv.c:(.text+0x320): undefined reference to `rpi_firmware_get'
> > > vc4_drv.c:(.text+0x320): relocation truncated to fit: R_AARCH64_CALL26 against undefined symbol `rpi_firmware_get'
> > > vc4_drv.c:(.text+0x34c): undefined reference to `rpi_firmware_property'
> > > vc4_drv.c:(.text+0x34c): relocation truncated to fit: R_AARCH64_CALL26 against undefined symbol `rpi_firmware_property'
> > > vc4_drv.c:(.text+0x354): undefined reference to `rpi_firmware_put'
> > > vc4_drv.c:(.text+0x354): relocation truncated to fit: R_AARCH64_CALL26 against undefined symbol `rpi_firmware_put'
> > > 
> > > Make DRM_VC4 depends on RASPBERRYPI_FIRMWARE || COMPILE_TEST to fix this.
> > > 
> > > Fixes: c406ad5e4a85 ("drm/vc4: Notify the firmware when DRM is in charge")
> > > Reported-by: Hulk Robot <hulkci@...wei.com>
> > > Signed-off-by: Zheng Bin <zhengbin13@...wei.com>
> > > ---
> > > v2: follow Maxime's advise, add RASPBERRYPI_FIRMWARE as an additional depends
> > >   drivers/gpu/drm/vc4/Kconfig | 1 +
> > >   1 file changed, 1 insertion(+)
> > > 
> > > diff --git a/drivers/gpu/drm/vc4/Kconfig b/drivers/gpu/drm/vc4/Kconfig
> > > index de3424fed2fc..92d74ba7c449 100644
> > > --- a/drivers/gpu/drm/vc4/Kconfig
> > > +++ b/drivers/gpu/drm/vc4/Kconfig
> > > @@ -2,6 +2,7 @@
> > >   config DRM_VC4
> > >   	tristate "Broadcom VC4 Graphics"
> > >   	depends on ARCH_BCM || ARCH_BCM2835 || COMPILE_TEST
> > > +	depends on RASPBERRYPI_FIRMWARE || COMPILE_TEST
> > Why do we need the || COMPILE_TEST here?
> > 
> > The rpi_firmware_get, _property and _put functions aren't define if
> > RASPBERRYPI_FIRMWARE, so we need that dependency every time, even if
> > COMPILE_TEST is set?
> 
> include/soc/bcm2835/raspberrypi-firmware.h
> 
> #if IS_ENABLED(CONFIG_RASPBERRYPI_FIRMWARE)
> 
> struct rpi_firmware *rpi_firmware_get(struct device_node
> *firmware_node);/_property/_put
> 
> #else    -->empty function
> 
>  static inline struct rpi_firmware *rpi_firmware_get(struct device_node
> *firmware_node)/_property/_put
> {
>          return NULL;
>  }
> #endif
> 
> 
> We can refer to drivers/pwm/Kconfig
> 
> config PWM_RASPBERRYPI_POE
>          tristate "Raspberry Pi Firwmware PoE Hat PWM support"
>          # Make sure not 'y' when RASPBERRYPI_FIRMWARE is 'm'. This can only
>         # happen when COMPILE_TEST=y, hence the added !RASPBERRYPI_FIRMWARE.
>          depends on RASPBERRYPI_FIRMWARE || (COMPILE_TEST &&
> !RASPBERRYPI_FIRMWARE)  -->There is no need to add (&&
> !RASPBERRYPI_FIRMWARE)

Oh, so you're fixing the case where vc4 would be built-in, but the
firmware driver a module?

I guess that makes sense, but the comment definitely helps there. And
the (COMPILE_TEST && !RASPBERRYPI_FIRMWARE) is also needed, since it
wouldn't fix the issue you're trying to fix for COMPILE_TEST otherwise.

Maxime

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