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GET /api/patches/808544/?format=api
{ "id": 808544, "url": "http://patchwork.ozlabs.org/api/patches/808544/?format=api", "web_url": "http://patchwork.ozlabs.org/project/linux-pci/patch/20170901072744.2409-4-dja@axtens.net/", "project": { "id": 28, "url": "http://patchwork.ozlabs.org/api/projects/28/?format=api", "name": "Linux PCI development", "link_name": "linux-pci", "list_id": "linux-pci.vger.kernel.org", "list_email": "linux-pci@vger.kernel.org", "web_url": null, "scm_url": null, "webscm_url": null, "list_archive_url": "", "list_archive_url_format": "", "commit_url_format": "" }, "msgid": "<20170901072744.2409-4-dja@axtens.net>", "list_archive_url": null, "date": "2017-09-01T07:27:44", "name": "[v3,3/3] drm: documentation for default display device", "commit_ref": null, "pull_url": null, "state": "not-applicable", "archived": false, "hash": "49f2d45332a993e2c2f1a9b8e29a66c1666fdc1f", "submitter": { "id": 65792, "url": "http://patchwork.ozlabs.org/api/people/65792/?format=api", "name": "Daniel Axtens", "email": "dja@axtens.net" }, "delegate": null, "mbox": "http://patchwork.ozlabs.org/project/linux-pci/patch/20170901072744.2409-4-dja@axtens.net/mbox/", "series": [ { "id": 959, "url": "http://patchwork.ozlabs.org/api/series/959/?format=api", "web_url": "http://patchwork.ozlabs.org/project/linux-pci/list/?series=959", "date": "2017-09-01T07:27:41", "name": "Split default display handling out from VGA arbiter", "version": 3, "mbox": "http://patchwork.ozlabs.org/series/959/mbox/" } ], "comments": "http://patchwork.ozlabs.org/api/patches/808544/comments/", "check": "pending", "checks": "http://patchwork.ozlabs.org/api/patches/808544/checks/", "tags": {}, "related": [], "headers": { "Return-Path": "<linux-pci-owner@vger.kernel.org>", "X-Original-To": "incoming@patchwork.ozlabs.org", "Delivered-To": "patchwork-incoming@bilbo.ozlabs.org", "Authentication-Results": [ "ozlabs.org;\n\tspf=none (mailfrom) smtp.mailfrom=vger.kernel.org\n\t(client-ip=209.132.180.67; helo=vger.kernel.org;\n\tenvelope-from=linux-pci-owner@vger.kernel.org;\n\treceiver=<UNKNOWN>)", "ozlabs.org; dkim=pass (1024-bit key;\n\tunprotected) header.d=axtens.net header.i=@axtens.net\n\theader.b=\"qM/nOp5F\"; dkim-atps=neutral" ], "Received": [ "from vger.kernel.org (vger.kernel.org [209.132.180.67])\n\tby ozlabs.org (Postfix) with ESMTP id 3xk9pK5V4Kz9s81\n\tfor <incoming@patchwork.ozlabs.org>;\n\tFri, 1 Sep 2017 17:28:41 +1000 (AEST)", "(majordomo@vger.kernel.org) by vger.kernel.org via listexpand\n\tid S1751404AbdIAH2l (ORCPT <rfc822;incoming@patchwork.ozlabs.org>);\n\tFri, 1 Sep 2017 03:28:41 -0400", "from mail-pf0-f196.google.com ([209.85.192.196]:36290 \"EHLO\n\tmail-pf0-f196.google.com\" rhost-flags-OK-OK-OK-OK) by vger.kernel.org\n\twith ESMTP id S1751354AbdIAH2k (ORCPT\n\t<rfc822;linux-pci@vger.kernel.org>); Fri, 1 Sep 2017 03:28:40 -0400", "by mail-pf0-f196.google.com with SMTP id k3so1181132pfc.3\n\tfor <linux-pci@vger.kernel.org>; Fri, 01 Sep 2017 00:28:40 -0700 (PDT)", "from localhost.localdomain (124-171-202-56.dyn.iinet.net.au.\n\t[124.171.202.56]) by smtp.gmail.com with ESMTPSA id\n\tl30sm2430300pgc.61.2017.09.01.00.28.33\n\t(version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128);\n\tFri, 01 Sep 2017 00:28:39 -0700 (PDT)" ], "DKIM-Signature": "v=1; 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\n\tFri, 01 Sep 2017 00:28:39 -0700 (PDT)", "From": "Daniel Axtens <dja@axtens.net>", "To": "linux-pci@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,\n\tlinux-arm-kernel@lists.infradead.org", "Cc": "benh@kernel.crashing.org, z.liuxinliang@hisilicon.com,\n\tzourongrong@gmail.com, catalin.marinas@arm.com,\n\twill.deacon@arm.com, gabriele.paoloni@huawei.com,\n\thelgaas@kernel.org, airlied@linux.ie, daniel.vetter@intel.com,\n\talex.williamson@redhat.com, dri-devel@lists.freedesktop.org,\n\tlukas@wunner.de, ard.biesheuvel@linaro.org,\n\tlorenzo.pieralisi@arm.com, Daniel Axtens <dja@axtens.net>", "Subject": "[PATCH v3 3/3] drm: documentation for default display device", "Date": "Fri, 1 Sep 2017 17:27:44 +1000", "Message-Id": "<20170901072744.2409-4-dja@axtens.net>", "X-Mailer": "git-send-email 2.11.0", "In-Reply-To": "<20170901072744.2409-1-dja@axtens.net>", "References": "<20170901072744.2409-1-dja@axtens.net>", "Sender": "linux-pci-owner@vger.kernel.org", "Precedence": "bulk", "List-ID": "<linux-pci.vger.kernel.org>", "X-Mailing-List": "linux-pci@vger.kernel.org" }, "content": "We have refactored and extended this - document it.\n\nSigned-off-by: Daniel Axtens <dja@axtens.net>\n---\n Documentation/gpu/default_display.rst | 93 +++++++++++++++++++++++++++++++++++\n Documentation/gpu/index.rst | 1 +\n 2 files changed, 94 insertions(+)\n create mode 100644 Documentation/gpu/default_display.rst", "diff": "diff --git a/Documentation/gpu/default_display.rst b/Documentation/gpu/default_display.rst\nnew file mode 100644\nindex 000000000000..3c190611564e\n--- /dev/null\n+++ b/Documentation/gpu/default_display.rst\n@@ -0,0 +1,93 @@\n+=======================\n+Default Display Devices\n+=======================\n+\n+Overview\n+========\n+\n+.. kernel-doc:: drivers/gpu/vga/default_display.c\n+\t\t:doc: overview\n+\n+\n+Why do we need this?\n+====================\n+\n+The default device is used to set the ``boot_vga`` per-device sysfs\n+file, which is used by user-space. Most notably, Xorg reads this file\n+via libpciaccess in order to facilitate auto-configuration.\n+\n+\n+History\n+=======\n+\n+When the VGA arbiter was introduced, it would pick a default device on\n+boot. As the arbiter exists to arbitrate access to legacy resources,\n+it would only pick a card that could be accessed through legacy areas.\n+(See the :doc:`vgaarbiter` documentation for more.)\n+\n+The arbiter was later extended on x86 and IA64 to consider the EFI\n+framebuffer.\n+\n+This is all well and good if you have legacy resources or\n+EFI. However, some systems do not have either of those. For example,\n+on POWER8: [0]_\n+\n+ - There is no IO space at all\n+\n+ - We configure the 32-bit MMIO window to be around 3..4G (to avoid\n+ overlapping with DMA space below it).\n+\n+So effectively, there is no path to the legacy areas.\n+\n+This means the VGA arbiter will not pick a default device on these\n+platforms. So, on powerpc, a class hook was added to mark a default\n+device (``arch/powerpc/kernel/pci-common.c``), independent of the\n+arbiter.\n+\n+When this issue arose on an arm64 system, it was decided that a generic\n+approach would be better than more special cases. Therefore, the\n+default device selection was factored out, and it now operates using\n+the priority list described in the Overview.\n+\n+API\n+===\n+\n+Public\n+------\n+\n+.. kernel-doc:: drivers/gpu/vga/default_display.c\n+\t\t:export:\n+\n+Private\n+-------\n+\n+.. kernel-doc:: drivers/gpu/vga/default_display.c\n+\t\t:internal:\n+\n+Future Work\n+===========\n+\n+There is no support for non-PCI VGA devices being marked as default.\n+The following comment, extracted from an earlier version of\n+:c:func:`pci_default_display()` might help:\n+\n+ If your VGA default device is not PCI, you'll have to override this\n+ and return NULL here. In this case, I assume it will not conflict\n+ with any PCI card. If this is not true, I'll have to define two\n+ archs hooks for enabling/disabling the VGA default device if that\n+ is possible. \n+\n+ This may be a problem with real _ISA_ VGA cards, in addition to a\n+ PCI one. I don't know at this point how to deal with that card. Can\n+ theirs IOs be disabled at all ? If not, then I suppose it's a matter\n+ of having the proper arch hook telling us about it, so we basically\n+ never allow anybody to succeed a ``vga_get()``...\n+\n+Currently there is also no way to support non-VGA-class PCI devices as\n+default display devices.\n+\n+\n+References\n+==========\n+\t \n+.. [0] https://www.spinics.net/lists/linux-pci/msg64142.html\ndiff --git a/Documentation/gpu/index.rst b/Documentation/gpu/index.rst\nindex 35d673bf9b56..8083d84f2334 100644\n--- a/Documentation/gpu/index.rst\n+++ b/Documentation/gpu/index.rst\n@@ -16,6 +16,7 @@ Linux GPU Driver Developer's Guide\n tegra\n tinydrm\n vc4\n+ default_display\n vga-switcheroo\n vgaarbiter\n bridge/dw-hdmi\n", "prefixes": [ "v3", "3/3" ] }