diff options
| -rw-r--r-- | Documentation/DocBook/drm.tmpl | 125 |
1 files changed, 74 insertions, 51 deletions
diff --git a/Documentation/DocBook/drm.tmpl b/Documentation/DocBook/drm.tmpl index 0e0390ece122..641db5cb656c 100644 --- a/Documentation/DocBook/drm.tmpl +++ b/Documentation/DocBook/drm.tmpl @@ -697,55 +697,16 @@ char *date;</synopsis> respectively. The conversion is handled by the DRM core without any driver-specific support. </para> - <para> - Similar to global names, GEM file descriptors are also used to share GEM - objects across processes. They offer additional security: as file - descriptors must be explicitly sent over UNIX domain sockets to be shared - between applications, they can't be guessed like the globally unique GEM - names. - </para> - <para> - Drivers that support GEM file descriptors, also known as the DRM PRIME - API, must set the DRIVER_PRIME bit in the struct - <structname>drm_driver</structname> - <structfield>driver_features</structfield> field, and implement the - <methodname>prime_handle_to_fd</methodname> and - <methodname>prime_fd_to_handle</methodname> operations. - </para> - <para> - <synopsis>int (*prime_handle_to_fd)(struct drm_device *dev, - struct drm_file *file_priv, uint32_t handle, - uint32_t flags, int *prime_fd); - int (*prime_fd_to_handle)(struct drm_device *dev, - struct drm_file *file_priv, int prime_fd, - uint32_t *handle);</synopsis> - Those two operations convert a handle to a PRIME file descriptor and - vice versa. Drivers must use the kernel dma-buf buffer sharing framework - to manage the PRIME file descriptors. - </para> - <para> - While non-GEM drivers must implement the operations themselves, GEM - drivers must use the <function>drm_gem_prime_handle_to_fd</function> - and <function>drm_gem_prime_fd_to_handle</function> helper functions. - Those helpers rely on the driver - <methodname>gem_prime_export</methodname> and - <methodname>gem_prime_import</methodname> operations to create a dma-buf - instance from a GEM object (dma-buf exporter role) and to create a GEM - object from a dma-buf instance (dma-buf importer role). - </para> - <para> - <synopsis>struct dma_buf * (*gem_prime_export)(struct drm_device *dev, - struct drm_gem_object *obj, - int flags); - struct drm_gem_object * (*gem_prime_import)(struct drm_device *dev, - struct dma_buf *dma_buf);</synopsis> - These two operations are mandatory for GEM drivers that support DRM - PRIME. - </para> - <sect4> - <title>DRM PRIME Helper Functions Reference</title> -!Pdrivers/gpu/drm/drm_prime.c PRIME Helpers - </sect4> + <para> + GEM also supports buffer sharing with dma-buf file descriptors through + PRIME. GEM-based drivers must use the provided helpers functions to + implement the exporting and importing correctly. See <xref linkend="drm-prime-support" />. + Since sharing file descriptors is inherently more secure than the + easily guessable and global GEM names it is the preferred buffer + sharing mechanism. Sharing buffers through GEM names is only supported + for legacy userspace. Furthermore PRIME also allows cross-device + buffer sharing since it is based on dma-bufs. + </para> </sect3> <sect3 id="drm-gem-objects-mapping"> <title>GEM Objects Mapping</title> @@ -868,10 +829,10 @@ char *date;</synopsis> abstracted from the client in libdrm. </para> </sect3> - <sect2> + <sect3> <title>GEM Function Reference</title> !Edrivers/gpu/drm/drm_gem.c - </sect2> + </sect3> </sect2> <sect2> <title>VMA Offset Manager</title> @@ -879,6 +840,68 @@ char *date;</synopsis> !Edrivers/gpu/drm/drm_vma_manager.c !Iinclude/drm/drm_vma_manager.h </sect2> + <sect2 id="drm-prime-support"> + <title>PRIME Buffer Sharing</title> + <para> + PRIME is the cross device buffer sharing framework in drm, originally + created for the OPTIMUS range of multi-gpu platforms. To userspace + PRIME buffers are dma-buf based file descriptors. + </para> + <sect3> + <title>Overview and Driver Interface</title> + <para> + Similar to GEM global names, PRIME file descriptors are + also used to share buffer objects across processes. They offer + additional security: as file descriptors must be explicitly sent over + UNIX domain sockets to be shared between applications, they can't be + guessed like the globally unique GEM names. + </para> + <para> + Drivers that support the PRIME + API must set the DRIVER_PRIME bit in the struct + <structname>drm_driver</structname> + <structfield>driver_features</structfield> field, and implement the + <methodname>prime_handle_to_fd</methodname> and + <methodname>prime_fd_to_handle</methodname> operations. + </para> + <para> + <synopsis>int (*prime_handle_to_fd)(struct drm_device *dev, + struct drm_file *file_priv, uint32_t handle, + uint32_t flags, int *prime_fd); +int (*prime_fd_to_handle)(struct drm_device *dev, + struct drm_file *file_priv, int prime_fd, + uint32_t *handle);</synopsis> + Those two operations convert a handle to a PRIME file descriptor and + vice versa. Drivers must use the kernel dma-buf buffer sharing framework + to manage the PRIME file descriptors. Similar to the mode setting + API PRIME is agnostic to the underlying buffer object manager, as + long as handles are 32bit unsinged integers. + </para> + <para> + While non-GEM drivers must implement the operations themselves, GEM + drivers must use the <function>drm_gem_prime_handle_to_fd</function> + and <function>drm_gem_prime_fd_to_handle</function> helper functions. + Those helpers rely on the driver + <methodname>gem_prime_export</methodname> and + <methodname>gem_prime_import</methodname> operations to create a dma-buf + instance from a GEM object (dma-buf exporter role) and to create a GEM + object from a dma-buf instance (dma-buf importer role). + </para> + <para> + <synopsis>struct dma_buf * (*gem_prime_export)(struct drm_device *dev, + struct drm_gem_object *obj, + int flags); +struct drm_gem_object * (*gem_prime_import)(struct drm_device *dev, + struct dma_buf *dma_buf);</synopsis> + These two operations are mandatory for GEM drivers that support + PRIME. + </para> + </sect3> + <sect3> + <title>PRIME Helper Functions Reference</title> +!Pdrivers/gpu/drm/drm_prime.c PRIME Helpers + </sect3> + </sect2> </sect1> <!-- Internals: mode setting --> |