| Message ID | 1390485025-16840-1-git-send-email-daniel.vetter@ffwll.ch (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
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@gmail.com> > Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com> > Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch> > --- > 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>
On Fri, Jan 24, 2014 at 12:13:11PM +0100, Laurent Pinchart wrote: > 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@gmail.com> > > Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com> > > Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch> > > --- > > 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 ? I've gone through the entire section to remove all GEM-specific language and missed the title. That's some good fail right there ;-) I'm going with buffer objects, which I think is the most established language for gfx memory management - GL also uses it in specs. [snip] > > + 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. Also opted for buffer object here. Other suggestions applies unchaged. Thanks, Daniel
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 @@ -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 @@ -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>
- 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@gmail.com> Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch> --- Documentation/DocBook/drm.tmpl | 129 ++++++++++++++++++++++------------------- 1 file changed, 70 insertions(+), 59 deletions(-)