lkml.org 
[lkml]   [2022]   [Jun]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 1/2] of: create of_root if no dtb provided
Le Thu, 23 Jun 2022 22:43:26 -0500,
frowand.list@gmail.com a écrit :

>
> +/*
> + * __dtb_empty_root_begin[] magically created by cmd_dt_S_dtb in
> + * scripts/Makefile.lib
> + */
> +extern void *__dtb_empty_root_begin;
> +
> /*
> * of_fdt_limit_memory - limit the number of regions in the /memory node
> * @limit: maximum entries
> @@ -1332,8 +1338,13 @@ bool __init early_init_dt_scan(void *params)
> */
> void __init unflatten_device_tree(void)
> {

Hi Frank,

This function is only defined when CONFIG_OF_EARLY_FLATTREE is enabled.
Which means that on platforms that do not select this, the default
empty device-tree creation will not be done.

This configuration option is selected by the platform and not by the
user. On x86, only one config enables this (X86_INTEL_CE) which means
this won't work on all the other platforms even if CONFIG_OF is
selected. I would need this to work by only selected CONFIG_OF.
That's why I decided to add the of_root creation in of_core_init()
using a function (of_fdt_unflatten()) that is provided if CONFIG_OF is
defined.

> - __unflatten_device_tree(initial_boot_params, NULL, &of_root,
> + if (!initial_boot_params) {
> + initial_boot_params = (void *) __dtb_empty_root_begin;
> + unflatten_and_copy_device_tree();
> + } else {
> + __unflatten_device_tree(initial_boot_params, NULL, &of_root,
> early_init_dt_alloc_memory_arch, false);
> + }
>
> /* Get pointer to "/chosen" and "/aliases" nodes for use everywhere */
> of_alias_scan(early_init_dt_alloc_memory_arch);
> @@ -1373,6 +1384,12 @@ void __init unflatten_and_copy_device_tree(void)
> unflatten_device_tree();
> }
>
> +void __init setup_of(void)
> +{
> + if (!of_root)
> + unflatten_device_tree();
> +}
> +
> #ifdef CONFIG_SYSFS
> static ssize_t of_fdt_raw_read(struct file *filp, struct kobject *kobj,
> struct bin_attribute *bin_attr,
> diff --git a/include/linux/of_fdt.h b/include/linux/of_fdt.h
> index d69ad5bb1eb1..4566876db351 100644
> --- a/include/linux/of_fdt.h
> +++ b/include/linux/of_fdt.h
> @@ -81,6 +81,7 @@ extern const void *of_flat_dt_match_machine(const void *default_match,
> /* Other Prototypes */
> extern void unflatten_device_tree(void);
> extern void unflatten_and_copy_device_tree(void);
> +extern void setup_of(void);
> extern void early_init_devtree(void *);
> extern void early_get_first_memblock_info(void *, phys_addr_t *);
> #else /* CONFIG_OF_EARLY_FLATTREE */
> @@ -91,6 +92,7 @@ static inline void early_init_fdt_reserve_self(void) {}
> static inline const char *of_flat_dt_get_machine_name(void) { return NULL; }
> static inline void unflatten_device_tree(void) {}
> static inline void unflatten_and_copy_device_tree(void) {}
> +static inline void of_setup(void) {}

Shouldn't this be setup_of(void) ?

--
Clément Léger,
Embedded Linux and Kernel engineer at Bootlin
https://bootlin.com

\
 
 \ /
  Last update: 2022-06-24 14:18    [W:0.063 / U:3.320 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site