[PATCH v5 0/3] DRM: allow to use mmuless devices

[PATCH v5 0/3] DRM: allow to use mmuless devices

[Benjamin Gaignard]

version 5:
- rebased on drm-for-v4.10 tag
- set get_unmapped_area field if FB_PROVIDE_GET_FB_UNMAPPED_AREA is
  defined 
- since version 4 dma_mmap_wc() issue will be fixed on architecture side,
  either by my patch (submitted, under review)
  http://www.armlinux.org.uk/developer/patches/viewpatch.php?id=8633/1	
  or by what is doing Vladimir about noMMU support on Cortex-M:
  http://www.spinics.net/lists/arm-kernel/msg548764.html

version 4:
- add documentation about drm_gem_cma_get_unmapped_area()
- introduce FB_PROVIDE_GET_FB_UNMAPPED_AREA configuration flag for get_fb_unmapped_area()
- I have also send the first patch (https://lkml.org/lkml/2016/12/1/308) to make dma_mmap_wc
  works on ARM noMMU platform, assuming that is patch will be accepted there is no more
  needs to call vm_ioremap in cma helpers.

version 3:
- split the original patch in 3 parts, it should be more easy to review like
  this.
- duplicate drm_fb_cma_helper.c and drm_gem_cma_helper.c into nommu version
- add a configuration flag for drm_vm.c 

There are some MCU platforms, like stm32f4, which don't have MMU
but have hardware display IP where is it possible to implement a
drm/kms driver.

Obviously that start by removing MMU configuration flag from Kconfig.
But while coding the driver for stm32f4 (on discovery board to have enough memory)
we have already identify few other pieces of code that need to be change.
We have been inspired by what already exist in v4l2 where using mmuless devices
is possible.

Since we have only use cma helpers we only have partial view of what could be
needed for other part of drm/kms framework.

Benjamin Gaignard (3):
  fbmem: add a default get_fb_unmapped_area function
  drm: compile drm_vm.c only when needed
  drm: allow to use mmuless SoC

 Documentation/gpu/drm-mm.rst         | 11 ++++++
 drivers/gpu/drm/Kconfig              |  9 ++++-
 drivers/gpu/drm/Makefile             |  3 +-
 drivers/gpu/drm/drm_gem_cma_helper.c | 71 ++++++++++++++++++++++++++++++++++++
 drivers/gpu/drm/drm_legacy.h         |  7 ++++
 drivers/gpu/drm/nouveau/Kconfig      |  1 +
 drivers/video/fbdev/Kconfig          |  8 ++++
 drivers/video/fbdev/core/fbmem.c     | 18 ++++++++-
 include/drm/drm_gem_cma_helper.h     | 17 +++++++++
 9 files changed, 141 insertions(+), 4 deletions(-)

-- 
1.9.1

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[PATCH v5 1/3] fbmem: add a default get_fb_unmapped_area function

[Benjamin Gaignard]

Allow generic frame-buffer to provide a default
get_fb_unmapped_area function if specific devices need it.

Usually this function is defined in architecture directories but
define it here may limit code duplication especially for all ARM
platforms without MMU.

version 5:
- set get_unmapped_area field if FB_PROVIDE_GET_FB_UNMAPPED_AREA is
  defined

version 4:
- introdude a configuration flag to be independent of architecture

Signed-off-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
---
 drivers/video/fbdev/Kconfig      |  8 ++++++++
 drivers/video/fbdev/core/fbmem.c | 18 +++++++++++++++++-
 2 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/drivers/video/fbdev/Kconfig b/drivers/video/fbdev/Kconfig
index 5d3b0db..922e4ea 100644
--- a/drivers/video/fbdev/Kconfig
+++ b/drivers/video/fbdev/Kconfig
@@ -138,6 +138,14 @@ config FB_SYS_IMAGEBLIT
 	  blitting. This is used by drivers that don't provide their own
 	  (accelerated) version and the framebuffer is in system RAM.
 
+config FB_PROVIDE_GET_FB_UNMAPPED_AREA
+	bool
+	depends on FB
+	default n
+	---help---
+	  Allow generic frame-buffer to provide get_fb_unmapped_area
+	  function.
+
 menuconfig FB_FOREIGN_ENDIAN
 	bool "Framebuffer foreign endianness support"
 	depends on FB
diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c
index 76c1ad9..069fe79 100644
--- a/drivers/video/fbdev/core/fbmem.c
+++ b/drivers/video/fbdev/core/fbmem.c
@@ -1492,6 +1492,21 @@ static long fb_compat_ioctl(struct file *file, unsigned int cmd,
 	return 0;
 }
 
+#ifdef CONFIG_FB_PROVIDE_GET_FB_UNMAPPED_AREA
+unsigned long get_fb_unmapped_area(struct file *filp,
+				   unsigned long addr, unsigned long len,
+				   unsigned long pgoff, unsigned long flags)
+{
+	struct fb_info * const info = filp->private_data;
+	unsigned long fb_size = PAGE_ALIGN(info->fix.smem_len);
+
+	if (pgoff > fb_size || len > fb_size - pgoff)
+		return -EINVAL;
+
+	return (unsigned long)info->screen_base + pgoff;
+}
+#endif
+
 static const struct file_operations fb_fops = {
 	.owner =	THIS_MODULE,
 	.read =		fb_read,
@@ -1503,7 +1518,8 @@ static long fb_compat_ioctl(struct file *file, unsigned int cmd,
 	.mmap =		fb_mmap,
 	.open =		fb_open,
 	.release =	fb_release,
-#ifdef HAVE_ARCH_FB_UNMAPPED_AREA
+#if defined(HAVE_ARCH_FB_UNMAPPED_AREA) || \
+    defined(CONFIG_FB_PROVIDE_GET_FB_UNMAPPED_AREA)
 	.get_unmapped_area = get_fb_unmapped_area,
 #endif
 #ifdef CONFIG_FB_DEFERRED_IO
-- 
1.9.1

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[PATCH v5 2/3] drm: compile drm_vm.c only when needed

[Benjamin Gaignard]

drm_vm.c functions are only need for DRM_LEGACY and DRM_NOUVEAU.
Use a new DRM_VM to define when drm_vm.c in needed.

stub drm_legacy_vma_flush() to avoid compilation issues

version 4:
- a "config DRM_VM" in Kconfig

Signed-off-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
---
 drivers/gpu/drm/Kconfig         | 5 +++++
 drivers/gpu/drm/Makefile        | 3 ++-
 drivers/gpu/drm/drm_legacy.h    | 7 +++++++
 drivers/gpu/drm/nouveau/Kconfig | 1 +
 4 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
index 7ecfff7..f799696 100644
--- a/drivers/gpu/drm/Kconfig
+++ b/drivers/gpu/drm/Kconfig
@@ -121,6 +121,10 @@ config DRM_KMS_CMA_HELPER
 	help
 	  Choose this if you need the KMS CMA helper functions
 
+config DRM_VM
+	bool
+	depends on DRM
+
 source "drivers/gpu/drm/i2c/Kconfig"
 
 source "drivers/gpu/drm/arm/Kconfig"
@@ -250,6 +254,7 @@ source "drivers/gpu/drm/meson/Kconfig"
 menuconfig DRM_LEGACY
 	bool "Enable legacy drivers (DANGEROUS)"
 	depends on DRM
+	select DRM_VM
 	help
 	  Enable legacy DRI1 drivers. Those drivers expose unsafe and dangerous
 	  APIs to user-space, which can be used to circumvent access
diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile
index 57f2fad..50b749e 100644
--- a/drivers/gpu/drm/Makefile
+++ b/drivers/gpu/drm/Makefile
@@ -5,7 +5,7 @@
 drm-y       :=	drm_auth.o drm_bufs.o drm_cache.o \
 		drm_context.o drm_dma.o \
 		drm_fops.o drm_gem.o drm_ioctl.o drm_irq.o \
-		drm_lock.o drm_memory.o drm_drv.o drm_vm.o \
+		drm_lock.o drm_memory.o drm_drv.o \
 		drm_scatter.o drm_pci.o \
 		drm_platform.o drm_sysfs.o drm_hashtab.o drm_mm.o \
 		drm_crtc.o drm_fourcc.o drm_modes.o drm_edid.o \
@@ -18,6 +18,7 @@ drm-y       :=	drm_auth.o drm_bufs.o drm_cache.o \
 		drm_plane.o drm_color_mgmt.o drm_print.o \
 		drm_dumb_buffers.o drm_mode_config.o
 
+drm-$(CONFIG_DRM_VM) += drm_vm.o
 drm-$(CONFIG_COMPAT) += drm_ioc32.o
 drm-$(CONFIG_DRM_GEM_CMA_HELPER) += drm_gem_cma_helper.o
 drm-$(CONFIG_PCI) += ati_pcigart.o
diff --git a/drivers/gpu/drm/drm_legacy.h b/drivers/gpu/drm/drm_legacy.h
index c6f422e..e4bb5ad 100644
--- a/drivers/gpu/drm/drm_legacy.h
+++ b/drivers/gpu/drm/drm_legacy.h
@@ -74,7 +74,14 @@ int drm_legacy_getmap_ioctl(struct drm_device *dev, void *data,
 int drm_legacy_mapbufs(struct drm_device *d, void *v, struct drm_file *f);
 int drm_legacy_dma_ioctl(struct drm_device *d, void *v, struct drm_file *f);
 
+#ifdef CONFIG_DRM_VM
 void drm_legacy_vma_flush(struct drm_device *d);
+#else
+static inline void drm_legacy_vma_flush(struct drm_device *d)
+{
+	/* do nothing */
+}
+#endif
 
 /*
  * AGP Support
diff --git a/drivers/gpu/drm/nouveau/Kconfig b/drivers/gpu/drm/nouveau/Kconfig
index 2922a82..0f2f0af 100644
--- a/drivers/gpu/drm/nouveau/Kconfig
+++ b/drivers/gpu/drm/nouveau/Kconfig
@@ -16,6 +16,7 @@ config DRM_NOUVEAU
 	select INPUT if ACPI && X86
 	select THERMAL if ACPI && X86
 	select ACPI_VIDEO if ACPI && X86
+	select DRM_VM
 	help
 	  Choose this option for open-source NVIDIA support.
 
-- 
1.9.1

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[PATCH v5 3/3] drm: allow to use mmuless SoC

[Benjamin Gaignard]

Some SoC without MMU have display driver where a drm/kms driver
could be implemented.

Before doing such kind of thing drm/kms must allow to use mmuless devices.
This patch propose to remove MMU configuration flag and add a cma helper
function to help implementing mmuless display driver

version 4:
- add documentation about drm_gem_cma_get_unmapped_area()
- stub it MMU case

Signed-off-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
---
 Documentation/gpu/drm-mm.rst         | 11 ++++++
 drivers/gpu/drm/Kconfig              |  4 +-
 drivers/gpu/drm/drm_gem_cma_helper.c | 71 ++++++++++++++++++++++++++++++++++++
 include/drm/drm_gem_cma_helper.h     | 17 +++++++++
 4 files changed, 101 insertions(+), 2 deletions(-)

diff --git a/Documentation/gpu/drm-mm.rst b/Documentation/gpu/drm-mm.rst
index bca8085..9d4aa11 100644
--- a/Documentation/gpu/drm-mm.rst
+++ b/Documentation/gpu/drm-mm.rst
@@ -303,6 +303,17 @@ created.
 Drivers that want to map the GEM object upfront instead of handling page
 faults can implement their own mmap file operation handler.
 
+For platforms without MMU the GEM core provides a helper method
+:c:func:`drm_gem_cma_get_unmapped_area`. The mmap() routines will call
+this to get a proposed address for the mapping.
+
+To use :c:func:`drm_gem_cma_get_unmapped_area`, drivers must fill the
+struct :c:type:`struct file_operations <file_operations>` get_unmapped_area
+field with a pointer on :c:func:`drm_gem_cma_get_unmapped_area`.
+
+More detailed information about get_unmapped_area can be found in
+Documentation/nommu-mmap.txt
+
 Memory Coherency
 ----------------
 
diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
index f799696..c5b6f33 100644
--- a/drivers/gpu/drm/Kconfig
+++ b/drivers/gpu/drm/Kconfig
@@ -6,7 +6,7 @@
 #
 menuconfig DRM
 	tristate "Direct Rendering Manager (XFree86 4.1.0 and higher DRI support)"
-	depends on (AGP || AGP=n) && !EMULATED_CMPXCHG && MMU && HAS_DMA
+	depends on (AGP || AGP=n) && !EMULATED_CMPXCHG && HAS_DMA
 	select HDMI
 	select FB_CMDLINE
 	select I2C
@@ -98,7 +98,7 @@ config DRM_LOAD_EDID_FIRMWARE
 
 config DRM_TTM
 	tristate
-	depends on DRM
+	depends on DRM && MMU
 	help
 	  GPU memory management subsystem for devices with multiple
 	  GPU memory types. Will be enabled automatically if a device driver
diff --git a/drivers/gpu/drm/drm_gem_cma_helper.c b/drivers/gpu/drm/drm_gem_cma_helper.c
index 1d6c335..19908bb 100644
--- a/drivers/gpu/drm/drm_gem_cma_helper.c
+++ b/drivers/gpu/drm/drm_gem_cma_helper.c
@@ -358,6 +358,77 @@ int drm_gem_cma_mmap(struct file *filp, struct vm_area_struct *vma)
 }
 EXPORT_SYMBOL_GPL(drm_gem_cma_mmap);
 
+#ifndef CONFIG_MMU
+/**
+ * drm_gem_cma_get_unmapped_area - propose address for mapping in noMMU cases
+ * @filp: file object
+ * @addr: memory address
+ * @len: buffer size
+ * @pgoff: page offset
+ * @flags: memory flags
+ *
+ * This function is used in noMMU platforms to propose address mapping
+ * for a given buffer.
+ * It's intended to be used as a direct handler for the struct &file_operations
+ * .get_unmapped_area() operation.
+ *
+ * Returns:
+ * mapping address on success or a negative error code on failure.
+ */
+unsigned long drm_gem_cma_get_unmapped_area(struct file *filp,
+					    unsigned long addr,
+					    unsigned long len,
+					    unsigned long pgoff,
+					    unsigned long flags)
+{
+	struct drm_gem_cma_object *cma_obj;
+	struct drm_gem_object *obj = NULL;
+	struct drm_file *priv = filp->private_data;
+	struct drm_device *dev = priv->minor->dev;
+	struct drm_vma_offset_node *node;
+
+	if (drm_device_is_unplugged(dev))
+		return -ENODEV;
+
+	drm_vma_offset_lock_lookup(dev->vma_offset_manager);
+	node = drm_vma_offset_exact_lookup_locked(dev->vma_offset_manager,
+						  pgoff,
+						  len >> PAGE_SHIFT);
+	if (likely(node)) {
+		obj = container_of(node, struct drm_gem_object, vma_node);
+		/*
+		 * When the object is being freed, after it hits 0-refcnt it
+		 * proceeds to tear down the object. In the process it will
+		 * attempt to remove the VMA offset and so acquire this
+		 * mgr->vm_lock.  Therefore if we find an object with a 0-refcnt
+		 * that matches our range, we know it is in the process of being
+		 * destroyed and will be freed as soon as we release the lock -
+		 * so we have to check for the 0-refcnted object and treat it as
+		 * invalid.
+		 */
+		if (!kref_get_unless_zero(&obj->refcount))
+			obj = NULL;
+	}
+
+	drm_vma_offset_unlock_lookup(dev->vma_offset_manager);
+
+	if (!obj)
+		return -EINVAL;
+
+	if (!drm_vma_node_is_allowed(node, priv)) {
+		drm_gem_object_unreference_unlocked(obj);
+		return -EACCES;
+	}
+
+	cma_obj = to_drm_gem_cma_obj(obj);
+
+	drm_gem_object_unreference_unlocked(obj);
+
+	return cma_obj->vaddr ? (unsigned long)cma_obj->vaddr : -EINVAL;
+}
+EXPORT_SYMBOL_GPL(drm_gem_cma_get_unmapped_area);
+#endif
+
 #ifdef CONFIG_DEBUG_FS
 /**
  * drm_gem_cma_describe - describe a CMA GEM object for debugfs
diff --git a/include/drm/drm_gem_cma_helper.h b/include/drm/drm_gem_cma_helper.h
index acd6af8..2abcd51 100644
--- a/include/drm/drm_gem_cma_helper.h
+++ b/include/drm/drm_gem_cma_helper.h
@@ -53,6 +53,23 @@ struct drm_gem_cma_object *drm_gem_cma_create(struct drm_device *drm,
 
 extern const struct vm_operations_struct drm_gem_cma_vm_ops;
 
+#ifndef CONFIG_MMU
+unsigned long drm_gem_cma_get_unmapped_area(struct file *filp,
+					    unsigned long addr,
+					    unsigned long len,
+					    unsigned long pgoff,
+					    unsigned long flags);
+#else
+static inline unsigned long drm_gem_cma_get_unmapped_area(struct file *filp,
+							  unsigned long addr,
+							  unsigned long len,
+							  unsigned long pgoff,
+							  unsigned long flags)
+{
+	return -EINVAL;
+}
+#endif
+
 #ifdef CONFIG_DEBUG_FS
 void drm_gem_cma_describe(struct drm_gem_cma_object *obj, struct seq_file *m);
 #endif
-- 
1.9.1

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Re: [PATCH v5 3/3] drm: allow to use mmuless SoC

[Daniel Vetter]

On Wed, Jan 04, 2017 at 10:12:57AM +0100, Benjamin Gaignard wrote:
> Some SoC without MMU have display driver where a drm/kms driver
> could be implemented.
> 
> Before doing such kind of thing drm/kms must allow to use mmuless devices.
> This patch propose to remove MMU configuration flag and add a cma helper
> function to help implementing mmuless display driver
> 
> version 4:
> - add documentation about drm_gem_cma_get_unmapped_area()
> - stub it MMU case
> 
> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
> ---
>  Documentation/gpu/drm-mm.rst         | 11 ++++++
>  drivers/gpu/drm/Kconfig              |  4 +-
>  drivers/gpu/drm/drm_gem_cma_helper.c | 71 ++++++++++++++++++++++++++++++++++++
>  include/drm/drm_gem_cma_helper.h     | 17 +++++++++
>  4 files changed, 101 insertions(+), 2 deletions(-)
> 
> diff --git a/Documentation/gpu/drm-mm.rst b/Documentation/gpu/drm-mm.rst
> index bca8085..9d4aa11 100644
> --- a/Documentation/gpu/drm-mm.rst
> +++ b/Documentation/gpu/drm-mm.rst
> @@ -303,6 +303,17 @@ created.
>  Drivers that want to map the GEM object upfront instead of handling page
>  faults can implement their own mmap file operation handler.
>  
> +For platforms without MMU the GEM core provides a helper method
> +:c:func:`drm_gem_cma_get_unmapped_area`. The mmap() routines will call
> +this to get a proposed address for the mapping.
> +
> +To use :c:func:`drm_gem_cma_get_unmapped_area`, drivers must fill the
> +struct :c:type:`struct file_operations <file_operations>` get_unmapped_area
> +field with a pointer on :c:func:`drm_gem_cma_get_unmapped_area`.

I've switched this to the recommened struct member reference format, which
is &file_operations.get_unmapped_area and merged all 3 patches.

Thanks, Daniel

> +
> +More detailed information about get_unmapped_area can be found in
> +Documentation/nommu-mmap.txt
> +
>  Memory Coherency
>  ----------------
>  
> diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
> index f799696..c5b6f33 100644
> --- a/drivers/gpu/drm/Kconfig
> +++ b/drivers/gpu/drm/Kconfig
> @@ -6,7 +6,7 @@
>  #
>  menuconfig DRM
>  	tristate "Direct Rendering Manager (XFree86 4.1.0 and higher DRI support)"
> -	depends on (AGP || AGP=n) && !EMULATED_CMPXCHG && MMU && HAS_DMA
> +	depends on (AGP || AGP=n) && !EMULATED_CMPXCHG && HAS_DMA
>  	select HDMI
>  	select FB_CMDLINE
>  	select I2C
> @@ -98,7 +98,7 @@ config DRM_LOAD_EDID_FIRMWARE
>  
>  config DRM_TTM
>  	tristate
> -	depends on DRM
> +	depends on DRM && MMU
>  	help
>  	  GPU memory management subsystem for devices with multiple
>  	  GPU memory types. Will be enabled automatically if a device driver
> diff --git a/drivers/gpu/drm/drm_gem_cma_helper.c b/drivers/gpu/drm/drm_gem_cma_helper.c
> index 1d6c335..19908bb 100644
> --- a/drivers/gpu/drm/drm_gem_cma_helper.c
> +++ b/drivers/gpu/drm/drm_gem_cma_helper.c
> @@ -358,6 +358,77 @@ int drm_gem_cma_mmap(struct file *filp, struct vm_area_struct *vma)
>  }
>  EXPORT_SYMBOL_GPL(drm_gem_cma_mmap);
>  
> +#ifndef CONFIG_MMU
> +/**
> + * drm_gem_cma_get_unmapped_area - propose address for mapping in noMMU cases
> + * @filp: file object
> + * @addr: memory address
> + * @len: buffer size
> + * @pgoff: page offset
> + * @flags: memory flags
> + *
> + * This function is used in noMMU platforms to propose address mapping
> + * for a given buffer.
> + * It's intended to be used as a direct handler for the struct &file_operations
> + * .get_unmapped_area() operation.
> + *
> + * Returns:
> + * mapping address on success or a negative error code on failure.
> + */
> +unsigned long drm_gem_cma_get_unmapped_area(struct file *filp,
> +					    unsigned long addr,
> +					    unsigned long len,
> +					    unsigned long pgoff,
> +					    unsigned long flags)
> +{
> +	struct drm_gem_cma_object *cma_obj;
> +	struct drm_gem_object *obj = NULL;
> +	struct drm_file *priv = filp->private_data;
> +	struct drm_device *dev = priv->minor->dev;
> +	struct drm_vma_offset_node *node;
> +
> +	if (drm_device_is_unplugged(dev))
> +		return -ENODEV;
> +
> +	drm_vma_offset_lock_lookup(dev->vma_offset_manager);
> +	node = drm_vma_offset_exact_lookup_locked(dev->vma_offset_manager,
> +						  pgoff,
> +						  len >> PAGE_SHIFT);
> +	if (likely(node)) {
> +		obj = container_of(node, struct drm_gem_object, vma_node);
> +		/*
> +		 * When the object is being freed, after it hits 0-refcnt it
> +		 * proceeds to tear down the object. In the process it will
> +		 * attempt to remove the VMA offset and so acquire this
> +		 * mgr->vm_lock.  Therefore if we find an object with a 0-refcnt
> +		 * that matches our range, we know it is in the process of being
> +		 * destroyed and will be freed as soon as we release the lock -
> +		 * so we have to check for the 0-refcnted object and treat it as
> +		 * invalid.
> +		 */
> +		if (!kref_get_unless_zero(&obj->refcount))
> +			obj = NULL;
> +	}
> +
> +	drm_vma_offset_unlock_lookup(dev->vma_offset_manager);
> +
> +	if (!obj)
> +		return -EINVAL;
> +
> +	if (!drm_vma_node_is_allowed(node, priv)) {
> +		drm_gem_object_unreference_unlocked(obj);
> +		return -EACCES;
> +	}
> +
> +	cma_obj = to_drm_gem_cma_obj(obj);
> +
> +	drm_gem_object_unreference_unlocked(obj);
> +
> +	return cma_obj->vaddr ? (unsigned long)cma_obj->vaddr : -EINVAL;
> +}
> +EXPORT_SYMBOL_GPL(drm_gem_cma_get_unmapped_area);
> +#endif
> +
>  #ifdef CONFIG_DEBUG_FS
>  /**
>   * drm_gem_cma_describe - describe a CMA GEM object for debugfs
> diff --git a/include/drm/drm_gem_cma_helper.h b/include/drm/drm_gem_cma_helper.h
> index acd6af8..2abcd51 100644
> --- a/include/drm/drm_gem_cma_helper.h
> +++ b/include/drm/drm_gem_cma_helper.h
> @@ -53,6 +53,23 @@ struct drm_gem_cma_object *drm_gem_cma_create(struct drm_device *drm,
>  
>  extern const struct vm_operations_struct drm_gem_cma_vm_ops;
>  
> +#ifndef CONFIG_MMU
> +unsigned long drm_gem_cma_get_unmapped_area(struct file *filp,
> +					    unsigned long addr,
> +					    unsigned long len,
> +					    unsigned long pgoff,
> +					    unsigned long flags);
> +#else
> +static inline unsigned long drm_gem_cma_get_unmapped_area(struct file *filp,
> +							  unsigned long addr,
> +							  unsigned long len,
> +							  unsigned long pgoff,
> +							  unsigned long flags)
> +{
> +	return -EINVAL;
> +}
> +#endif
> +
>  #ifdef CONFIG_DEBUG_FS
>  void drm_gem_cma_describe(struct drm_gem_cma_object *obj, struct seq_file *m);
>  #endif
> -- 
> 1.9.1
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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