Hi Daniel, Thank you for the patch. One last round of nitpicking (including a typo fix, which gives me an excuse for a couple more comments :-)). On Thursday 23 January 2014 14:50:25 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. > > Cc: David Herrmann <dh.herrmann@xxxxxxxxx> > Cc: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx> > Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxx> > --- > Documentation/DocBook/drm.tmpl | 129 ++++++++++++++++++++------------------ > 1 file changed, 70 insertions(+), 59 deletions(-) > > diff --git a/Documentation/DocBook/drm.tmpl b/Documentation/DocBook/drm.tmpl > index ed1d6d289022..767318d5ddb6 100644 > --- a/Documentation/DocBook/drm.tmpl > +++ b/Documentation/DocBook/drm.tmpl [snip] > @@ -1052,6 +998,71 @@ int max_width, max_height;</synopsis> > <function>drm_framebuffer_unregister_private</function>. > </sect2> > <sect2> > + <title>Dumb GEM Objects</title> What about calling this "Dumb Memory Objects" (or something similar), as they're not specific to GEM ? > + <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 s/object suitable/suitable/ ? > + 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. What about s/objects/memory objects/ ? "object" alone is rather vague for people not too familiar with DRM/KMS. > + </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
