- This is _not_ a generic interface to create gem objects, but just an interface to make early boot services (like boot splash) with a generic KMS userspace driver possible. Hence it's better to move the documentation for this from the GEM section to the KMS section, next to the creation of framebuffer objects.
- Make it really clear that the returned handle isn't necessarily a GEM object (it can also be e.g. a TTM handle when running on top of vmwgfx).
- Add a paragraph to make it clear that this is just for unaccelarated userspace - gpu drivers need to have their own buffer object creation ioctl which is hardware specific.
Cc: Laurent Pinchart laurent.pinchart@ideasonboard.com> Signed-off-by: Daniel Vetter daniel.vetter@ffwll.ch --- Documentation/DocBook/drm.tmpl | 125 ++++++++++++++++++++++------------------- 1 file changed, 68 insertions(+), 57 deletions(-)
diff --git a/Documentation/DocBook/drm.tmpl b/Documentation/DocBook/drm.tmpl index ed1d6d289022..9c3fdd59c995 100644 --- a/Documentation/DocBook/drm.tmpl +++ b/Documentation/DocBook/drm.tmpl @@ -830,62 +830,6 @@ char *date;</synopsis> </para> </sect3> <sect3> - <title>Dumb GEM Objects</title> - <para> - The GEM API doesn't standardize GEM objects creation and leaves it to - driver-specific ioctls. While not an issue for full-fledged graphics - stacks that include device-specific userspace components (in libdrm for - instance), this limit makes DRM-based early boot graphics unnecessarily - complex. - </para> - <para> - Dumb GEM objects partly alleviate the problem by providing a standard - API to create dumb buffers suitable for scanout, which can then be used - to create KMS frame buffers. - </para> - <para> - To support dumb GEM objects drivers must implement the - <methodname>dumb_create</methodname>, - <methodname>dumb_destroy</methodname> and - <methodname>dumb_map_offset</methodname> operations. - </para> - <itemizedlist> - <listitem> - <synopsis>int (*dumb_create)(struct drm_file *file_priv, struct drm_device *dev, - struct drm_mode_create_dumb *args);</synopsis> - <para> - The <methodname>dumb_create</methodname> operation creates a GEM - object suitable for scanout based on the width, height and depth - from the struct <structname>drm_mode_create_dumb</structname> - argument. It fills the argument's <structfield>handle</structfield>, - <structfield>pitch</structfield> and <structfield>size</structfield> - fields with a handle for the newly created GEM object and its line - pitch and size in bytes. - </para> - </listitem> - <listitem> - <synopsis>int (*dumb_destroy)(struct drm_file *file_priv, struct drm_device *dev, - uint32_t handle);</synopsis> - <para> - The <methodname>dumb_destroy</methodname> operation destroys a dumb - GEM object created by <methodname>dumb_create</methodname>. - </para> - </listitem> - <listitem> - <synopsis>int (*dumb_map_offset)(struct drm_file *file_priv, struct drm_device *dev, - uint32_t handle, uint64_t *offset);</synopsis> - <para> - The <methodname>dumb_map_offset</methodname> operation associates an - mmap fake offset with the GEM object given by the handle and returns - it. Drivers must use the - <function>drm_gem_create_mmap_offset</function> function to - associate the fake offset as described in - <xref linkend="drm-gem-objects-mapping"/>. - </para> - </listitem> - </itemizedlist> - </sect3> - <sect3> <title>Memory Coherency</title> <para> When mapped to the device or used in a command buffer, backing pages @@ -970,7 +914,9 @@ int max_width, max_height;</synopsis> handle (or a list of memory handles for multi-planar formats) through the <parameter>drm_mode_fb_cmd2</parameter> argument. This document assumes that the driver uses GEM, those handles thus reference GEM - objects. + objects. But drivers are free to use their own backing storage object + handles, e.g. vmwgfx directly exposes special TTM handles to userspace + and so expects TTM handles in the create ioctl and not GEM objects. </para> <para> Drivers must first validate the requested frame buffer parameters passed @@ -1052,6 +998,71 @@ int max_width, max_height;</synopsis> <function>drm_framebuffer_unregister_private</function>. </sect2> <sect2> + <title>Dumb GEM Objects</title> + <para> + The KMS API doesn't standardize backing storage object creation and + leaves it to driver-specific ioctls. Furthermore actually creating a + buffer object even for GEM-based drivers is done through a + driver-specific ioctl - GEM only has a common userspace interface for + sharing and destroying objects. While not an issue for full-fledged + graphics stacks that include device-specific userspace components (in + libdrm for instance), this limit makes DRM-based early boot graphics + unnecessarily complex. + </para> + <para> + Dumb objects partly alleviate the problem by providing a standard + API to create dumb buffers suitable for scanout, which can then be used + to create KMS frame buffers. + </para> + <para> + To support dumb objects drivers must implement the + <methodname>dumb_create</methodname>, + <methodname>dumb_destroy</methodname> and + <methodname>dumb_map_offset</methodname> operations. + </para> + <itemizedlist> + <listitem> + <synopsis>int (*dumb_create)(struct drm_file *file_priv, struct drm_device *dev, + struct drm_mode_create_dumb *args);</synopsis> + <para> + The <methodname>dumb_create</methodname> operation creates a driver + object (GEM or TTM handle) object suitable for scanout based on the + width, height and depth from the struct + <structname>drm_mode_create_dumb</structname> argument. It fills the + argument's <structfield>handle</structfield>, + <structfield>pitch</structfield> and <structfield>size</structfield> + fields with a handle for the newly created object and its line + pitch and size in bytes. + </para> + </listitem> + <listitem> + <synopsis>int (*dumb_destroy)(struct drm_file *file_priv, struct drm_device *dev, + uint32_t handle);</synopsis> + <para> + The <methodname>dumb_destroy</methodname> operation destroys a dumb + object created by <methodname>dumb_create</methodname>. + </para> + </listitem> + <listitem> + <synopsis>int (*dumb_map_offset)(struct drm_file *file_priv, struct drm_device *dev, + uint32_t handle, uint64_t *offset);</synopsis> + <para> + The <methodname>dumb_map_offset</methodname> operation associates an + mmap fake offset with the object given by the handle and returns + it. Drivers must use the + <function>drm_gem_create_mmap_offset</function> function to + associate the fake offset as described in + <xref linkend="drm-gem-objects-mapping"/>. + </para> + </listitem> + </itemizedlist> + <para> + Note that dumb objects may not be used for gpu accelaration, as has been + attempted on some ARM embedded platforms. Such drivers really must have + a hardware-specific ioctl to allocate suitable objects. + </para> + </sect2> + <sect2> <title>Output Polling</title> <synopsis>void (*output_poll_changed)(struct drm_device *dev);</synopsis> <para>