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The push-to-system function forces a buffer out of video RAM. This decision should rather be made by the memory manager. By replacing the function with calls to the kunmap and unpin functions, the buffer's memory becomes available, but the buffer remains in VRAM until it's evicted by a pin operation. This patch replaces the remaining instances of drm_gem_vram_push_to_system() in ast and mgag200, and removes the function from DRM. Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de> Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch> Link: http://patchwork.freedesktop.org/patch/msgid/20190521110831.20200-2-tzimmermann@suse.de Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
97 lines
3.5 KiB
C
97 lines
3.5 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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#include <linux/module.h>
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/**
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* DOC: overview
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*
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* This library provides &struct drm_gem_vram_object (GEM VRAM), a GEM
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* buffer object that is backed by video RAM. It can be used for
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* framebuffer devices with dedicated memory. The video RAM can be
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* managed with &struct drm_vram_mm (VRAM MM). Both data structures are
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* supposed to be used together, but can also be used individually.
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*
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* With the GEM interface userspace applications create, manage and destroy
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* graphics buffers, such as an on-screen framebuffer. GEM does not provide
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* an implementation of these interfaces. It's up to the DRM driver to
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* provide an implementation that suits the hardware. If the hardware device
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* contains dedicated video memory, the DRM driver can use the VRAM helper
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* library. Each active buffer object is stored in video RAM. Active
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* buffer are used for drawing the current frame, typically something like
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* the frame's scanout buffer or the cursor image. If there's no more space
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* left in VRAM, inactive GEM objects can be moved to system memory.
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*
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* The easiest way to use the VRAM helper library is to call
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* drm_vram_helper_alloc_mm(). The function allocates and initializes an
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* instance of &struct drm_vram_mm in &struct drm_device.vram_mm . Use
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* &DRM_GEM_VRAM_DRIVER to initialize &struct drm_driver and
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* &DRM_VRAM_MM_FILE_OPERATIONS to initialize &struct file_operations;
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* as illustrated below.
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*
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* .. code-block:: c
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*
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* struct file_operations fops ={
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* .owner = THIS_MODULE,
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* DRM_VRAM_MM_FILE_OPERATION
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* };
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* struct drm_driver drv = {
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* .driver_feature = DRM_ ... ,
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* .fops = &fops,
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* DRM_GEM_VRAM_DRIVER
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* };
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*
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* int init_drm_driver()
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* {
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* struct drm_device *dev;
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* uint64_t vram_base;
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* unsigned long vram_size;
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* int ret;
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*
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* // setup device, vram base and size
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* // ...
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*
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* ret = drm_vram_helper_alloc_mm(dev, vram_base, vram_size,
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* &drm_gem_vram_mm_funcs);
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* if (ret)
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* return ret;
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* return 0;
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* }
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*
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* This creates an instance of &struct drm_vram_mm, exports DRM userspace
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* interfaces for GEM buffer management and initializes file operations to
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* allow for accessing created GEM buffers. With this setup, the DRM driver
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* manages an area of video RAM with VRAM MM and provides GEM VRAM objects
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* to userspace.
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*
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* To clean up the VRAM memory management, call drm_vram_helper_release_mm()
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* in the driver's clean-up code.
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*
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* .. code-block:: c
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*
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* void fini_drm_driver()
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* {
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* struct drm_device *dev = ...;
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*
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* drm_vram_helper_release_mm(dev);
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* }
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*
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* For drawing or scanout operations, buffer object have to be pinned in video
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* RAM. Call drm_gem_vram_pin() with &DRM_GEM_VRAM_PL_FLAG_VRAM or
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* &DRM_GEM_VRAM_PL_FLAG_SYSTEM to pin a buffer object in video RAM or system
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* memory. Call drm_gem_vram_unpin() to release the pinned object afterwards.
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*
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* A buffer object that is pinned in video RAM has a fixed address within that
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* memory region. Call drm_gem_vram_offset() to retrieve this value. Typically
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* it's used to program the hardware's scanout engine for framebuffers, set
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* the cursor overlay's image for a mouse cursor, or use it as input to the
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* hardware's draing engine.
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*
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* To access a buffer object's memory from the DRM driver, call
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* drm_gem_vram_kmap(). It (optionally) maps the buffer into kernel address
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* space and returns the memory address. Use drm_gem_vram_kunmap() to
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* release the mapping.
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*/
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MODULE_DESCRIPTION("DRM VRAM memory-management helpers");
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MODULE_LICENSE("GPL");
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