media: atmel: fix build when ISC=m and XISC=y

Building VIDEO_ATMEL_ISC as module and VIDEO_ATMEL_XISC as built-in
(or viceversa) causes build errors:

 or1k-linux-ld: drivers/media/platform/atmel/atmel-isc-base.o: in function `isc_async_complete':
 atmel-isc-base.c:(.text+0x40d0): undefined reference to `__this_module'
 or1k-linux-ld: atmel-isc-base.c:(.text+0x40f0): undefined reference to `__this_module'
 or1k-linux-ld: drivers/media/platform/atmel/atmel-isc-base.o:(.rodata+0x390): undefined reference to `__this_module'
 or1k-linux-ld: drivers/media/platform/atmel/atmel-isc-base.o:(__param+0x4): undefined reference to `__this_module'
 or1k-linux-ld: drivers/media/platform/atmel/atmel-isc-base.o:(__param+0x18): undefined reference to `__this_module'

This is caused by the file atmel-isc-base.c which is common code between
the two drivers.

The solution is to create another Kconfig symbol that is automatically
selected and generates the module atmel-isc-base.ko. This module can be
loaded when both drivers are modules, or built-in when at least one of them
is built-in.
Reported-by: kernel test robot <lkp@intel.com>
Fixes: c9aa9738 ("media: atmel: atmel-isc: add microchip-xisc driver")
Signed-off-by: Eugen Hristev <eugen.hristev@microchip.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

drivers/media/platform/atmel/Kconfig

@@ -8,6 +8,7 @@ config VIDEO_ATMEL_ISC
 	select VIDEOBUF2_DMA_CONTIG
 	select REGMAP_MMIO
 	select V4L2_FWNODE
+	select VIDEO_ATMEL_ISC_BASE
 	help
 	   This module makes the ATMEL Image Sensor Controller available
 	   as a v4l2 device.
@@ -19,10 +20,17 @@ config VIDEO_ATMEL_XISC
 	select VIDEOBUF2_DMA_CONTIG
 	select REGMAP_MMIO
 	select V4L2_FWNODE
+	select VIDEO_ATMEL_ISC_BASE
 	help
 	   This module makes the ATMEL eXtended Image Sensor Controller
 	   available as a v4l2 device.
 
+config VIDEO_ATMEL_ISC_BASE
+	tristate
+	default n
+	help
+	  ATMEL ISC and XISC common code base.
+
 config VIDEO_ATMEL_ISI
 	tristate "ATMEL Image Sensor Interface (ISI) support"
 	depends on VIDEO_V4L2 && OF

drivers/media/platform/atmel/Makefile

 # SPDX-License-Identifier: GPL-2.0-only
-atmel-isc-objs = atmel-sama5d2-isc.o atmel-isc-base.o
-atmel-xisc-objs = atmel-sama7g5-isc.o atmel-isc-base.o
+atmel-isc-objs = atmel-sama5d2-isc.o
+atmel-xisc-objs = atmel-sama7g5-isc.o
 
 obj-$(CONFIG_VIDEO_ATMEL_ISI) += atmel-isi.o
+obj-$(CONFIG_VIDEO_ATMEL_ISC_BASE) += atmel-isc-base.o
 obj-$(CONFIG_VIDEO_ATMEL_ISC) += atmel-isc.o
 obj-$(CONFIG_VIDEO_ATMEL_XISC) += atmel-xisc.o

drivers/media/platform/atmel/atmel-isc-base.c

@@ -378,6 +378,7 @@ int isc_clk_init(struct isc_device *isc)
 
 	return 0;
 }
+EXPORT_SYMBOL_GPL(isc_clk_init);
 
 void isc_clk_cleanup(struct isc_device *isc)
 {
@@ -392,6 +393,7 @@ void isc_clk_cleanup(struct isc_device *isc)
 			clk_unregister(isc_clk->clk);
 	}
 }
+EXPORT_SYMBOL_GPL(isc_clk_cleanup);
 
 static int isc_queue_setup(struct vb2_queue *vq,
 			    unsigned int *nbuffers, unsigned int *nplanes,
@@ -1578,6 +1580,7 @@ irqreturn_t isc_interrupt(int irq, void *dev_id)
 
 	return ret;
 }
+EXPORT_SYMBOL_GPL(isc_interrupt);
 
 static void isc_hist_count(struct isc_device *isc, u32 *min, u32 *max)
 {
@@ -2212,6 +2215,7 @@ const struct v4l2_async_notifier_operations isc_async_ops = {
 	.unbind = isc_async_unbind,
 	.complete = isc_async_complete,
 };
+EXPORT_SYMBOL_GPL(isc_async_ops);
 
 void isc_subdev_cleanup(struct isc_device *isc)
 {
@@ -2224,6 +2228,7 @@ void isc_subdev_cleanup(struct isc_device *isc)
 
 	INIT_LIST_HEAD(&isc->subdev_entities);
 }
+EXPORT_SYMBOL_GPL(isc_subdev_cleanup);
 
 int isc_pipeline_init(struct isc_device *isc)
 {
@@ -2264,6 +2269,7 @@ int isc_pipeline_init(struct isc_device *isc)
 
 	return 0;
 }
+EXPORT_SYMBOL_GPL(isc_pipeline_init);
 
 /* regmap configuration */
 #define ATMEL_ISC_REG_MAX    0xd5c
@@ -2273,4 +2279,9 @@ const struct regmap_config isc_regmap_config = {
 	.val_bits       = 32,
 	.max_register	= ATMEL_ISC_REG_MAX,
 };
+EXPORT_SYMBOL_GPL(isc_regmap_config);
 
+MODULE_AUTHOR("Songjun Wu");
+MODULE_AUTHOR("Eugen Hristev");
+MODULE_DESCRIPTION("Atmel ISC common code base");
+MODULE_LICENSE("GPL v2");