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X-OriginatorOrg: xilinx.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 16 Feb 2022 05:01:20.1625 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 6fe63f8d-53a3-4416-e9f2-08d9f1095f1f X-MS-Exchange-CrossTenant-Id: 657af505-d5df-48d0-8300-c31994686c5c X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=657af505-d5df-48d0-8300-c31994686c5c;Ip=[149.199.62.198];Helo=[xsj-pvapexch01.xlnx.xilinx.com] X-MS-Exchange-CrossTenant-AuthSource: DM3NAM02FT060.eop-nam02.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM5PR02MB2220 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Xilinx Alveo PCIe accelerator cards use flattened device tree to describe describe apertures in its PCIe BARs. Each device tree node represents an aperture and each aperture is an hardware unit which requires a driver. The product detail: https://www.xilinx.com/products/boards-and-kits/alveo.html Thus a base device tree is required. Then the Alveo card driver can load its flattened device tree and overlay it to the base tree. However device tree does not always exist. To resolve this, add OF_EMPTY_ROOT config. When it is selected and there is not a device tree, create an empty device tree root node. Signed-off-by: Sonal Santan Signed-off-by: Max Zhen Signed-off-by: Lizhi Hou --- drivers/of/Kconfig | 5 ++++ drivers/of/Makefile | 1 + drivers/of/of_empty_root.c | 51 ++++++++++++++++++++++++++++++++++++++ 3 files changed, 57 insertions(+) create mode 100644 drivers/of/of_empty_root.c diff --git a/drivers/of/Kconfig b/drivers/of/Kconfig index 80b5fd44ab1c..452d2316b47b 100644 --- a/drivers/of/Kconfig +++ b/drivers/of/Kconfig @@ -94,4 +94,9 @@ config OF_DMA_DEFAULT_COHERENT # arches should select this if DMA is coherent by default for OF devices bool =20 +config OF_EMPTY_ROOT + # driver which requires at least the empty base device tree to + # overlay its own device nodes should select this. + bool + endif # OF diff --git a/drivers/of/Makefile b/drivers/of/Makefile index e0360a44306e..c65364f32935 100644 --- a/drivers/of/Makefile +++ b/drivers/of/Makefile @@ -12,6 +12,7 @@ obj-$(CONFIG_OF_RESERVED_MEM) +=3D of_reserved_mem.o obj-$(CONFIG_OF_RESOLVE) +=3D resolver.o obj-$(CONFIG_OF_OVERLAY) +=3D overlay.o obj-$(CONFIG_OF_NUMA) +=3D of_numa.o +obj-$(CONFIG_OF_EMPTY_ROOT) +=3D of_empty_root.o =20 ifdef CONFIG_KEXEC_FILE ifdef CONFIG_OF_FLATTREE diff --git a/drivers/of/of_empty_root.c b/drivers/of/of_empty_root.c new file mode 100644 index 000000000000..5c429c7a27bd --- /dev/null +++ b/drivers/of/of_empty_root.c @@ -0,0 +1,51 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (C) 2022 Xilinx, Inc. + */ + +#include +#include + +#include "of_private.h" + +static int __init of_root_init(void) +{ + struct property *prop =3D NULL; + struct device_node *node; + __be32 *val =3D NULL; + + if (of_root) + return 0; + + pr_info("Create empty OF root node\n"); + node =3D kzalloc(sizeof(*node), GFP_KERNEL); + if (!node) + return -ENOMEM; + of_node_init(node); + node->full_name =3D "/"; + + prop =3D kcalloc(2, sizeof(*prop), GFP_KERNEL); + if (!prop) + return -ENOMEM; + + val =3D kzalloc(sizeof(*val), GFP_KERNEL); + if (!val) + return -ENOMEM; + *val =3D cpu_to_be32(sizeof(void *) / sizeof(u32)); + + prop->name =3D "#address-cells"; + prop->value =3D val; + prop->length =3D sizeof(u32); + of_add_property(node, prop); + prop++; + prop->name =3D "#size-cells"; + prop->value =3D val; + prop->length =3D sizeof(u32); + of_add_property(node, prop); + of_root =3D node; + for_each_of_allnodes(node) + __of_attach_node_sysfs(node); + + return 0; +} +pure_initcall(of_root_init); --=20 2.27.0