diff options
Diffstat (limited to 'drivers/gpu/drm/drm_gem_vram_helper.c')
| -rw-r--r-- | drivers/gpu/drm/drm_gem_vram_helper.c | 95 |
1 files changed, 90 insertions, 5 deletions
diff --git a/drivers/gpu/drm/drm_gem_vram_helper.c b/drivers/gpu/drm/drm_gem_vram_helper.c index cdf710be39da..8b2d5c945c95 100644 --- a/drivers/gpu/drm/drm_gem_vram_helper.c +++ b/drivers/gpu/drm/drm_gem_vram_helper.c @@ -1,5 +1,7 @@ // SPDX-License-Identifier: GPL-2.0-or-later +#include <linux/module.h> + #include <drm/drm_debugfs.h> #include <drm/drm_device.h> #include <drm/drm_drv.h> @@ -19,13 +21,93 @@ static const struct drm_gem_object_funcs drm_gem_vram_object_funcs; /** * DOC: overview * - * This library provides a GEM buffer object that is backed by video RAM - * (VRAM). It can be used for framebuffer devices with dedicated memory. + * This library provides &struct drm_gem_vram_object (GEM VRAM), a GEM + * buffer object that is backed by video RAM (VRAM). It can be used for + * framebuffer devices with dedicated memory. * * The data structure &struct drm_vram_mm and its helpers implement a memory - * manager for simple framebuffer devices with dedicated video memory. Buffer - * objects are either placed in video RAM or evicted to system memory. The rsp. - * buffer object is provided by &struct drm_gem_vram_object. + * manager for simple framebuffer devices with dedicated video memory. GEM + * VRAM buffer objects are either placed in the video memory or remain evicted + * to system memory. + * + * With the GEM interface userspace applications create, manage and destroy + * graphics buffers, such as an on-screen framebuffer. GEM does not provide + * an implementation of these interfaces. It's up to the DRM driver to + * provide an implementation that suits the hardware. If the hardware device + * contains dedicated video memory, the DRM driver can use the VRAM helper + * library. Each active buffer object is stored in video RAM. Active + * buffer are used for drawing the current frame, typically something like + * the frame's scanout buffer or the cursor image. If there's no more space + * left in VRAM, inactive GEM objects can be moved to system memory. + * + * The easiest way to use the VRAM helper library is to call + * drm_vram_helper_alloc_mm(). The function allocates and initializes an + * instance of &struct drm_vram_mm in &struct drm_device.vram_mm . Use + * &DRM_GEM_VRAM_DRIVER to initialize &struct drm_driver and + * &DRM_VRAM_MM_FILE_OPERATIONS to initialize &struct file_operations; + * as illustrated below. + * + * .. code-block:: c + * + * struct file_operations fops ={ + * .owner = THIS_MODULE, + * DRM_VRAM_MM_FILE_OPERATION + * }; + * struct drm_driver drv = { + * .driver_feature = DRM_ ... , + * .fops = &fops, + * DRM_GEM_VRAM_DRIVER + * }; + * + * int init_drm_driver() + * { + * struct drm_device *dev; + * uint64_t vram_base; + * unsigned long vram_size; + * int ret; + * + * // setup device, vram base and size + * // ... + * + * ret = drm_vram_helper_alloc_mm(dev, vram_base, vram_size); + * if (ret) + * return ret; + * return 0; + * } + * + * This creates an instance of &struct drm_vram_mm, exports DRM userspace + * interfaces for GEM buffer management and initializes file operations to + * allow for accessing created GEM buffers. With this setup, the DRM driver + * manages an area of video RAM with VRAM MM and provides GEM VRAM objects + * to userspace. + * + * To clean up the VRAM memory management, call drm_vram_helper_release_mm() + * in the driver's clean-up code. + * + * .. code-block:: c + * + * void fini_drm_driver() + * { + * struct drm_device *dev = ...; + * + * drm_vram_helper_release_mm(dev); + * } + * + * For drawing or scanout operations, buffer object have to be pinned in video + * RAM. Call drm_gem_vram_pin() with &DRM_GEM_VRAM_PL_FLAG_VRAM or + * &DRM_GEM_VRAM_PL_FLAG_SYSTEM to pin a buffer object in video RAM or system + * memory. Call drm_gem_vram_unpin() to release the pinned object afterwards. + * + * A buffer object that is pinned in video RAM has a fixed address within that + * memory region. Call drm_gem_vram_offset() to retrieve this value. Typically + * it's used to program the hardware's scanout engine for framebuffers, set + * the cursor overlay's image for a mouse cursor, or use it as input to the + * hardware's draing engine. + * + * To access a buffer object's memory from the DRM driver, call + * drm_gem_vram_kmap(). It (optionally) maps the buffer into kernel address + * space and returns the memory address. Use drm_gem_vram_kunmap() to + * release the mapping. */ /* @@ -1197,3 +1279,6 @@ drm_vram_helper_mode_valid(struct drm_device *dev, return drm_vram_helper_mode_valid_internal(dev, mode, max_bpp); } EXPORT_SYMBOL(drm_vram_helper_mode_valid); + +MODULE_DESCRIPTION("DRM VRAM memory-management helpers"); +MODULE_LICENSE("GPL"); |