On Wed, Dec 07, 2016 at 04:32:44PM +0200, Laurent Pinchart wrote:
Hi Benjamin,
Thank you for the patch.
On Wednesday 07 Dec 2016 11:06:51 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 | 69 +++++++++++++++++++++++++++++++++ include/drm/drm_gem_cma_helper.h | 17 +++++++++ 4 files changed, 99 insertions(+), 2 deletions(-)
diff --git a/Documentation/gpu/drm-mm.rst b/Documentation/gpu/drm-mm.rst index bca8085..6e7efab 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 GEM care provides a helper method
s/GEM care/the GEM core/
+: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 83ac815..0eae4ad 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..01016b1 100644 --- a/drivers/gpu/drm/drm_gem_cma_helper.c +++ b/drivers/gpu/drm/drm_gem_cma_helper.c @@ -358,6 +358,75 @@ 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.
I would add
"It's intended to be used as a direct handler for the :c:type:`struct file_operations <file_operations>` .get_unmapped_area() operation."
If' it's kernel-doc you can use shortcuts to autogenerate the links. Only works with kernel-doc comments though, not with .rst in general:
"It's intended to be used as a direct handler for the struct &file_operations .get_unmapped_area() operation."
And +1 from me on sprinkling links all over docs. We might want to do that for all the fbdev fops, for consistency.
Cheers, Daniel