From patchwork Tue Oct 21 10:49:36 2014 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Dheeraj Jamwal X-Patchwork-Id: 5117431 Return-Path: X-Original-To: patchwork-ltsi-dev@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.19.201]) by patchwork1.web.kernel.org (Postfix) with ESMTP id 1BD559F349 for ; Tue, 21 Oct 2014 11:33:55 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id EB8AB2010F for ; Tue, 21 Oct 2014 11:33:53 +0000 (UTC) Received: from mail.linuxfoundation.org (mail.linuxfoundation.org [140.211.169.12]) (using TLSv1.2 with cipher DHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 8064B20107 for ; Tue, 21 Oct 2014 11:33:52 +0000 (UTC) Received: from mail.linux-foundation.org (localhost [127.0.0.1]) by mail.linuxfoundation.org (Postfix) with ESMTP id 6E3EDF2C; Tue, 21 Oct 2014 11:05:42 +0000 (UTC) X-Original-To: ltsi-dev@lists.linuxfoundation.org Delivered-To: ltsi-dev@mail.linuxfoundation.org Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTPS id EC09AEF9 for ; Tue, 21 Oct 2014 11:05:39 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.7.6 Received: from mga01.intel.com (mga01.intel.com [192.55.52.88]) by smtp1.linuxfoundation.org (Postfix) with ESMTP id E8A1F2010C for ; Tue, 21 Oct 2014 11:05:38 +0000 (UTC) Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by fmsmga101.fm.intel.com with ESMTP; 21 Oct 2014 04:04:36 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.04,761,1406617200"; d="scan'208";a="617795482" Received: from ubuntu-desktop.png.intel.com ([10.221.122.25]) by fmsmga002.fm.intel.com with ESMTP; 21 Oct 2014 04:04:35 -0700 From: Dheeraj Jamwal To: ltsi-dev@lists.linuxfoundation.org Date: Tue, 21 Oct 2014 18:49:36 +0800 Message-Id: <1413889294-31328-377-git-send-email-dheerajx.s.jamwal@intel.com> X-Mailer: git-send-email 1.7.9.5 In-Reply-To: <1413889294-31328-1-git-send-email-dheerajx.s.jamwal@intel.com> References: <1413889294-31328-1-git-send-email-dheerajx.s.jamwal@intel.com> MIME-Version: 1.0 X-Spam-Status: No, score=-5.6 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_MED, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org Subject: [LTSI-dev] [PATCH 0376/1094] drm/doc: Clarify the dumb object interfaces X-BeenThere: ltsi-dev@lists.linuxfoundation.org X-Mailman-Version: 2.1.12 Precedence: list List-Id: "A list to discuss patches, development, and other things related to the LTSI project" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: ltsi-dev-bounces@lists.linuxfoundation.org Errors-To: ltsi-dev-bounces@lists.linuxfoundation.org X-Virus-Scanned: ClamAV using ClamSMTP From: Daniel Vetter - 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. v5: More typo fixes from Dieter. Cc: Dieter Nützel Cc: David Herrmann Cc: Laurent Pinchart Acked-by: Laurent Pinchart Reviewed-by: Alex Deucher Signed-off-by: Daniel Vetter (cherry picked from commit 065a5027dca8e9383ac308de4310e8e850b0cafb) Signed-off-by: Dheeraj Jamwal --- Documentation/DocBook/drm.tmpl | 133 ++++++++++++++++++++++------------------ 1 file changed, 72 insertions(+), 61 deletions(-) diff --git a/Documentation/DocBook/drm.tmpl b/Documentation/DocBook/drm.tmpl index 9adde25..e51cff1 100644 --- a/Documentation/DocBook/drm.tmpl +++ b/Documentation/DocBook/drm.tmpl @@ -838,62 +838,6 @@ char *date; - Dumb GEM Objects - - 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. - - - 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. - - - To support dumb GEM objects drivers must implement the - dumb_create, - dumb_destroy and - dumb_map_offset operations. - - - - int (*dumb_create)(struct drm_file *file_priv, struct drm_device *dev, - struct drm_mode_create_dumb *args); - - The dumb_create operation creates a GEM - object suitable for scanout based on the width, height and depth - from the struct drm_mode_create_dumb - argument. It fills the argument's handle, - pitch and size - fields with a handle for the newly created GEM object and its line - pitch and size in bytes. - - - - int (*dumb_destroy)(struct drm_file *file_priv, struct drm_device *dev, - uint32_t handle); - - The dumb_destroy operation destroys a dumb - GEM object created by dumb_create. - - - - int (*dumb_map_offset)(struct drm_file *file_priv, struct drm_device *dev, - uint32_t handle, uint64_t *offset); - - The dumb_map_offset operation associates an - mmap fake offset with the GEM object given by the handle and returns - it. Drivers must use the - drm_gem_create_mmap_offset function to - associate the fake offset as described in - . - - - - - Memory Coherency When mapped to the device or used in a command buffer, backing pages @@ -976,9 +920,11 @@ int max_width, max_height; 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 drm_mode_fb_cmd2 argument. This document - assumes that the driver uses GEM, those handles thus reference GEM - objects. + the drm_mode_fb_cmd2 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. Drivers must first validate the requested frame buffer parameters passed @@ -1000,7 +946,7 @@ int max_width, max_height; - The initailization of the new framebuffer instance is finalized with a + The initialization of the new framebuffer instance is finalized with a call to drm_framebuffer_init which takes a pointer to DRM frame buffer operations (struct drm_framebuffer_funcs). Note that this function @@ -1060,6 +1006,71 @@ int max_width, max_height; drm_framebuffer_unregister_private. + Dumb Buffer Objects + + 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. + + + 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. + + + To support dumb objects drivers must implement the + dumb_create, + dumb_destroy and + dumb_map_offset operations. + + + + int (*dumb_create)(struct drm_file *file_priv, struct drm_device *dev, + struct drm_mode_create_dumb *args); + + The dumb_create operation creates a driver + object (GEM or TTM handle) suitable for scanout based on the + width, height and depth from the struct + drm_mode_create_dumb argument. It fills the + argument's handle, + pitch and size + fields with a handle for the newly created object and its line + pitch and size in bytes. + + + + int (*dumb_destroy)(struct drm_file *file_priv, struct drm_device *dev, + uint32_t handle); + + The dumb_destroy operation destroys a dumb + object created by dumb_create. + + + + int (*dumb_map_offset)(struct drm_file *file_priv, struct drm_device *dev, + uint32_t handle, uint64_t *offset); + + The dumb_map_offset operation associates an + mmap fake offset with the object given by the handle and returns + it. Drivers must use the + drm_gem_create_mmap_offset function to + associate the fake offset as described in + . + + + + + Note that dumb objects may not be used for gpu acceleration, as has been + attempted on some ARM embedded platforms. Such drivers really must have + a hardware-specific ioctl to allocate suitable buffer objects. + + + Output Polling void (*output_poll_changed)(struct drm_device *dev); @@ -2142,7 +2153,7 @@ void intel_crt_init(struct drm_device *dev) set the display_info width_mm and height_mm fields if they haven't been set - already (for instance at initilization time when a fixed-size panel is + already (for instance at initialization time when a fixed-size panel is attached to the connector). The mode width_mm and height_mm fields are only used internally during EDID parsing and should not be set when creating modes manually.