On Tue, Jan 25, 2022 at 09:48:07PM -0800, Lizhi Hou wrote:
> Add OF_EMPTY_ROOT config. When it is selected and there is not a device
> tree, create an empty device tree root node.
Maybe add some description about why a empty device tree root node is
needed. Note that the Patch #0 will not be present in the repo when the
series will be merged, so add your description here please.
>
> Signed-off-by: Sonal Santan <sonal.santan@xxxxxxxxxx>
> Signed-off-by: Max Zhen <max.zhen@xxxxxxxxxx>
> Signed-off-by: Lizhi Hou <lizhi.hou@xxxxxxxxxx>
> ---
> drivers/of/Kconfig | 3 +++
> drivers/of/Makefile | 1 +
> drivers/of/of_empty_root.c | 51 ++++++++++++++++++++++++++++++++++++++
> 3 files changed, 55 insertions(+)
> create mode 100644 drivers/of/of_empty_root.c
>
> diff --git a/drivers/of/Kconfig b/drivers/of/Kconfig
> index 80b5fd44ab1c..42afb126f91a 100644
> --- a/drivers/of/Kconfig
> +++ b/drivers/of/Kconfig
> @@ -94,4 +94,7 @@ config OF_DMA_DEFAULT_COHERENT
> # arches should select this if DMA is coherent by default for OF devices
> bool
>
> +config OF_EMPTY_ROOT
> + bool
Also some descriptions for better understanding?
Thanks,
Yilun
> +
> 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-$(CONFIG_OF_RESERVED_MEM) += of_reserved_mem.o
> obj-$(CONFIG_OF_RESOLVE) += resolver.o
> obj-$(CONFIG_OF_OVERLAY) += overlay.o
> obj-$(CONFIG_OF_NUMA) += of_numa.o
> +obj-$(CONFIG_OF_EMPTY_ROOT) += of_empty_root.o
>
> 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 <linux/of.h>
> +#include <linux/slab.h>
> +
> +#include "of_private.h"
> +
> +static int __init of_root_init(void)
> +{
> + struct property *prop = NULL;
> + struct device_node *node;
> + __be32 *val = NULL;
> +
> + if (of_root)
> + return 0;
> +
> + pr_info("Create empty OF root node\n");
> + node = kzalloc(sizeof(*node), GFP_KERNEL);
> + if (!node)
> + return -ENOMEM;
> + of_node_init(node);
> + node->full_name = "/";
> +
> + prop = kcalloc(2, sizeof(*prop), GFP_KERNEL);
> + if (!prop)
> + return -ENOMEM;
> +
> + val = kzalloc(sizeof(*val), GFP_KERNEL);
> + if (!val)
> + return -ENOMEM;
> + *val = cpu_to_be32(sizeof(void *) / sizeof(u32));
> +
> + prop->name = "#address-cells";
> + prop->value = val;
> + prop->length = sizeof(u32);
> + of_add_property(node, prop);
> + prop++;
> + prop->name = "#size-cells";
> + prop->value = val;
> + prop->length = sizeof(u32);
> + of_add_property(node, prop);
> + of_root = node;
> + for_each_of_allnodes(node)
> + __of_attach_node_sysfs(node);
> +
> + return 0;
> +}
> +pure_initcall(of_root_init);
> --
> 2.27.0
