Hi Daniel, Thank you for the patch. On Friday 24 January 2014 17:58:40 Daniel Vetter wrote: > - 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. > > v2: Clarify that the documentation doesn't just apply to GEM-based > drivers only but is now generally valid, as suggested by David. > > v3: Polish the intro sentence a bit and one s/objects/handles/ for > clarification, both suggested by Laurent. > > v4: More text polish from Laurent's review. > > Cc: David Herrmann <dh.herrmann@xxxxxxxxx> > Cc: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx> > Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxx> Acked-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx> > --- > Documentation/DocBook/drm.tmpl | 131 ++++++++++++++++++++------------------ > 1 file changed, 71 insertions(+), 60 deletions(-) > > diff --git a/Documentation/DocBook/drm.tmpl b/Documentation/DocBook/drm.tmpl > index ed1d6d289022..67cfe184749c 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 @@ -968,9 +912,11 @@ int max_width, max_height;</synopsis> > Frame buffers rely on the underneath memory manager for low-level > memory operations. When creating a frame buffer applications pass a memory > 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. > + the <parameter>drm_mode_fb_cmd2</parameter> argument. For drivers using > + GEM as their userspace buffer management interface this would be a GEM > + handle. Drivers are however 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 handles. > </para> > <para> > Drivers must first validate the requested frame buffer parameters > passed @@ -992,7 +938,7 @@ int max_width, max_height;</synopsis> > </para> > > <para> > - The initailization of the new framebuffer instance is finalized with a > + The initilization of the new framebuffer instance is finalized with a > call to <function>drm_framebuffer_init</function> which takes a pointer > to DRM frame buffer operations (struct > <structname>drm_framebuffer_funcs</structname>). Note that this function > @@ -1052,6 +998,71 @@ int max_width, max_height;</synopsis> > <function>drm_framebuffer_unregister_private</function>. > </sect2> > <sect2> > + <title>Dumb Buffer 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) 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 buffer objects. > + </para> > + </sect2> > + <sect2> > <title>Output Polling</title> > <synopsis>void (*output_poll_changed)(struct drm_device > *dev);</synopsis> <para> -- Regards, Laurent Pinchart _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/dri-devel
