linux-kernel - [PATCH] staging: vc04_services: Re-add dependency on HAS_DMA to BCM2835

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Date:   Mon, 25 Apr 2022 14:18:25 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Nicolas Saenz Julienne <nsaenz@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Florian Fainelli <f.fainelli@...il.com>,
        Ray Jui <rjui@...adcom.com>,
        Scott Branden <sbranden@...adcom.com>,
        bcm-kernel-feedback-list@...adcom.com
Cc:     Mauro Carvalho Chehab <mchehab@...nel.org>,
        Arnd Bergmann <arnd@...db.de>,
        linux-rpi-kernel@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-staging@...ts.linux.dev, linux-kernel@...r.kernel.org,
        Geert Uytterhoeven <geert@...ux-m68k.org>
Subject: [PATCH] staging: vc04_services: Re-add dependency on HAS_DMA to BCM2835_VCHIQ

Thanks to stubs for the NO_DMA=y case, drivers that use the DMA API can
be compile-tested on systems that do not support DMA.  Hence the
dependency of BCM2835_VCHIQ on HAS_DMA was dropped to increase compile
coverage.

Unfortunately compilers became smarter, leading to new failures.
E.g. for a CONFIG_SUN3=y allmodconfig kernel with gcc 9.4.0:

    drivers/staging/vc04_services/interface/vchiq_arm/vchiq_2835_arm.c: In function ‘free_pagelist’:
    arch/m68k/include/asm/string.h:72:25: warning: argument 2 null where non-null expected [-Wnonnull]
       72 | #define memcpy(d, s, n) __builtin_memcpy(d, s, n)
	  |                         ^~~~~~~~~~~~~~~~~~~~~~~~~
    drivers/staging/vc04_services/interface/vchiq_arm/vchiq_2835_arm.c:614:4: note: in expansion of macro ‘memcpy’
      614 |    memcpy((char *)kmap(pages[0]) +
	  |    ^~~~~~
    arch/m68k/include/asm/string.h:72:25: note: in a call to built-in function ‘__builtin_memcpy’
       72 | #define memcpy(d, s, n) __builtin_memcpy(d, s, n)
	  |                         ^~~~~~~~~~~~~~~~~~~~~~~~~
    drivers/staging/vc04_services/interface/vchiq_arm/vchiq_2835_arm.c:614:4: note: in expansion of macro ‘memcpy’
      614 |    memcpy((char *)kmap(pages[0]) +
	  |    ^~~~~~

This happens because the compiler can trace back the source pointer to a
allocation by dma_alloc_attrs(), which always returns NULL if NO_DMA=y.

Avoid this reinstating the dependency of the BCM2835_VCHIQ symbol on
HAS_DMA, and by restricting the selection of BCM2835_VCHIQ.

Signed-off-by: Geert Uytterhoeven <geert@...ux-m68k.org>
---
 drivers/staging/vc04_services/Kconfig                | 1 +
 drivers/staging/vc04_services/bcm2835-audio/Kconfig  | 2 +-
 drivers/staging/vc04_services/bcm2835-camera/Kconfig | 4 ++--
 3 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/staging/vc04_services/Kconfig b/drivers/staging/vc04_services/Kconfig
index cb7c82403dbf22cb..31e58c9d1a110441 100644
--- a/drivers/staging/vc04_services/Kconfig
+++ b/drivers/staging/vc04_services/Kconfig
@@ -13,6 +13,7 @@ if BCM_VIDEOCORE
 
 config BCM2835_VCHIQ
 	tristate "BCM2835 VCHIQ"
+	depends on HAS_DMA
 	imply VCHIQ_CDEV
 	help
 		Broadcom BCM2835 and similar SoCs have a VPU called VideoCore. This config
diff --git a/drivers/staging/vc04_services/bcm2835-audio/Kconfig b/drivers/staging/vc04_services/bcm2835-audio/Kconfig
index d32ea348e846f2c0..5a3a5279551eb702 100644
--- a/drivers/staging/vc04_services/bcm2835-audio/Kconfig
+++ b/drivers/staging/vc04_services/bcm2835-audio/Kconfig
@@ -3,7 +3,7 @@ config SND_BCM2835
 	tristate "BCM2835 Audio"
 	depends on (ARCH_BCM2835 || COMPILE_TEST) && SND
 	select SND_PCM
-	select BCM2835_VCHIQ
+	select BCM2835_VCHIQ if HAS_DMA
 	help
 	  Say Y or M if you want to support BCM2835 built in audio
 
diff --git a/drivers/staging/vc04_services/bcm2835-camera/Kconfig b/drivers/staging/vc04_services/bcm2835-camera/Kconfig
index dcda565f9b38090f..870c9afb223a220b 100644
--- a/drivers/staging/vc04_services/bcm2835-camera/Kconfig
+++ b/drivers/staging/vc04_services/bcm2835-camera/Kconfig
@@ -3,8 +3,8 @@ config VIDEO_BCM2835
 	tristate "BCM2835 Camera"
 	depends on MEDIA_SUPPORT
 	depends on VIDEO_DEV && (ARCH_BCM2835 || COMPILE_TEST)
-	select BCM2835_VCHIQ
-	select BCM2835_VCHIQ_MMAL
+	select BCM2835_VCHIQ if HAS_DMA
+	select BCM2835_VCHIQ_MMAL if HAS_DMA
 	select VIDEOBUF2_VMALLOC
 	select BTREE
 	help
-- 
2.25.1