[U-Boot] [PATCH v3 10/12] libfdt: Add overlay application function

[Simon Glass <sjg@chromium.org>]

Hi Maxime,

On 24 June 2016 at 08:27, Maxime Ripard
<maxime.ripard@free-electrons.com> wrote:
> The device tree overlays are a good way to deal with user-modifyable
> boards or boards with some kind of an expansion mechanism where we can
> easily plug new board in (like the BBB, the Raspberry Pi or the CHIP).
>
> Add a new function to merge overlays with a base device tree.
>
> Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
> ---
>  include/libfdt.h         |  30 ++++
>  lib/Kconfig              |   5 +
>  lib/libfdt/Makefile      |   2 +
>  lib/libfdt/fdt_overlay.c | 381 +++++++++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 418 insertions(+)
>  create mode 100644 lib/libfdt/fdt_overlay.c
>

Is there a change log?

> diff --git a/include/libfdt.h b/include/libfdt.h
> index b8758de3ae54..039ecb0c1ba7 100644
> --- a/include/libfdt.h
> +++ b/include/libfdt.h
> @@ -1747,6 +1747,36 @@ int fdt_add_subnode(void *fdt, int parentoffset, const char *name);
>   */
>  int fdt_del_node(void *fdt, int nodeoffset);
>
> +/**
> + * fdt_overlay_apply - Applies a DT overlay on a base DT
> + * @fdt: pointer to the base device tree blob
> + * @fdto: pointer to the device tree overlay blob
> + *
> + * fdt_overlay_apply() will apply the given device tree overlay on the
> + * given base device tree.
> + *
> + * Expect the base device tree to be modified, even if the function
> + * returns an error.
> + *
> + * returns:
> + *     0, on success
> + *     -FDT_ERR_NOSPACE, there's not enough space in the base device tree
> + *     -FDT_ERR_NOTFOUND, the overlay points to some inexistant nodes or
> + *             properties in the base DT
> + *     -FDT_ERR_BADPHANDLE, the phandles in the overlay do not have the right
> + *             magic
> + *     -FDT_ERR_INTERNAL,
> + *     -FDT_ERR_BADLAYOUT,
> + *     -FDT_ERR_BADMAGIC,
> + *     -FDT_ERR_BADOFFSET,
> + *     -FDT_ERR_BADPATH,
> + *     -FDT_ERR_BADVERSION,
> + *     -FDT_ERR_BADSTRUCTURE,
> + *     -FDT_ERR_BADSTATE,
> + *     -FDT_ERR_TRUNCATED, standard meanings
> + */
> +int fdt_overlay_apply(void *fdt, void *fdto);
> +
>  /**********************************************************************/
>  /* Debugging / informational functions                                */
>  /**********************************************************************/
> diff --git a/lib/Kconfig b/lib/Kconfig
> index 02ca4058d37e..16ff01a2cd37 100644
> --- a/lib/Kconfig
> +++ b/lib/Kconfig
> @@ -139,6 +139,11 @@ config OF_LIBFDT
>           particular compatible nodes. The library operates on a flattened
>           version of the device tree.
>
> +config OF_LIBFDT_OVERLAY
> +       bool "Enable the FDT library overlay support"
> +       help
> +         This enables the FDT library (libfdt) overlay support.
> +
>  config SPL_OF_LIBFDT
>         bool "Enable the FDT library for SPL"
>         default y if SPL_OF_CONTROL
> diff --git a/lib/libfdt/Makefile b/lib/libfdt/Makefile
> index 8b86c15904cb..6ef8290f4e09 100644
> --- a/lib/libfdt/Makefile
> +++ b/lib/libfdt/Makefile
> @@ -15,3 +15,5 @@ obj-y += \
>         fdt_empty_tree.o \
>         fdt_addresses.o \
>         fdt_region.o
> +
> +obj-$(CONFIG_OF_LIBFDT_OVERLAY) += fdt_overlay.o
> diff --git a/lib/libfdt/fdt_overlay.c b/lib/libfdt/fdt_overlay.c
> new file mode 100644
> index 000000000000..5835a90afafe
> --- /dev/null
> +++ b/lib/libfdt/fdt_overlay.c
> @@ -0,0 +1,381 @@
> +#include "libfdt_env.h"
> +
> +#include <fdt.h>
> +#include <libfdt.h>
> +
> +#include "libfdt_internal.h"
> +
> +static uint32_t overlay_get_target_phandle(const void *fdto, int fragment)
> +{
> +       const uint32_t *val;
> +       int len;
> +
> +       val = fdt_getprop(fdto, fragment, "target", &len);
> +       if (!val || (*val == 0xffffffff) || (len != sizeof(*val)))
> +               return 0;
> +
> +       return fdt32_to_cpu(*val);
> +}
> +
> +static int overlay_get_target(const void *fdt, const void *fdto,
> +                             int fragment)

function comment please.

> +{
> +       uint32_t phandle;
> +       const char *path;
> +
> +       /* Try first to do a phandle based lookup */
> +       phandle = overlay_get_target_phandle(fdto, fragment);
> +       if (phandle)
> +               return fdt_node_offset_by_phandle(fdt, phandle);
> +
> +       /* And then a path based lookup */
> +       path = fdt_getprop(fdto, fragment, "target-path", NULL);
> +       if (!path)
> +               return -FDT_ERR_NOTFOUND;
> +
> +       return fdt_path_offset(fdt, path);
> +}
> +
> +static int overlay_phandle_add_offset(void *fdt, int node,
> +                                     const char *name, uint32_t delta)

function comment please.

> +{
> +       const uint32_t *val;
> +       uint32_t adj_val;
> +       int len;
> +
> +       val = fdt_getprop(fdt, node, name, &len);
> +       if (!val)
> +               return len;
> +
> +       if (len != sizeof(*val))
> +               return -FDT_ERR_BADSTRUCTURE;
> +
> +       adj_val = fdt32_to_cpu(*val);
> +       adj_val += delta;
> +
> +       return fdt_setprop_inplace_u32(fdt, node, name, adj_val);
> +}
> +
> +static int overlay_adjust_node_phandles(void *fdto, int node,
> +                                       uint32_t delta)

function comment please.

> +{
> +       bool found = false;
> +       int child;
> +       int ret;
> +
> +       ret = overlay_phandle_add_offset(fdto, node, "phandle", delta);
> +       if (ret && ret != -FDT_ERR_NOTFOUND)
> +               return ret;
> +
> +       if (!ret)
> +               found = true;
> +
> +       ret = overlay_phandle_add_offset(fdto, node, "linux,phandle", delta);
> +       if (ret && ret != -FDT_ERR_NOTFOUND)
> +               return ret;
> +
> +       /*
> +        * If neither phandle nor linux,phandle have been found return
> +        * an error.
> +        */
> +       if (!found && !ret)
> +               return ret;
> +
> +       fdt_for_each_subnode(fdto, child, node)
> +               overlay_adjust_node_phandles(fdto, child, delta);
> +
> +       return 0;
> +}
> +
> +static int overlay_adjust_local_phandles(void *fdto, uint32_t delta)
> +{
> +       /*
> +        * Start adjusting the phandles from the overlay root
> +        */
> +       return overlay_adjust_node_phandles(fdto, 0, delta);
> +}
> +
> +static int overlay_update_local_node_references(void *fdto,
> +                                               int tree_node,
> +                                               int fixup_node,
> +                                               uint32_t delta)
> +{

Please add function comments for all of these.


> +       int fixup_prop;
> +       int fixup_child;
> +       int ret;
> +
> +       fdt_for_each_property_offset(fixup_prop, fdto, fixup_node) {
> +               const uint32_t *val = NULL;
> +               uint32_t adj_val, index;
> +               const char *name;
> +               int fixup_len;
> +               int tree_len;
> +
> +               val = fdt_getprop_by_offset(fdto, fixup_prop,
> +                                           &name, &fixup_len);
> +               if (!val)
> +                       return fixup_len;
> +               index = fdt32_to_cpu(*val);
> +
> +               val = fdt_getprop(fdto, tree_node, name, &tree_len);
> +               if (!val)
> +                       return tree_len;
> +
> +               adj_val = fdt32_to_cpu(*(val + (index / sizeof(uint32_t))));
> +               adj_val += delta;
> +               adj_val = cpu_to_fdt32(adj_val);
> +
> +               ret = fdt_setprop_inplace_namelen_by_index(fdto, tree_node,
> +                                                          name, strlen(name),
> +                                                          index, &adj_val,
> +                                                          sizeof(adj_val));
> +               if (ret)
> +                       return ret;
> +       }
> +
> +       fdt_for_each_subnode(fdto, fixup_child, fixup_node) {
> +               const char *fixup_child_name = fdt_get_name(fdto, fixup_child,
> +                                                           NULL);
> +               int tree_child;
> +
> +               tree_child = fdt_subnode_offset(fdto, tree_node,
> +                                               fixup_child_name);
> +               if (tree_child < 0)
> +                       return tree_child;
> +
> +               ret = overlay_update_local_node_references(fdto,
> +                                                          tree_child,
> +                                                          fixup_child,
> +                                                          delta);
> +               if (ret)
> +                       return ret;
> +       }
> +
> +       return 0;
> +}
> +
> +static int overlay_update_local_references(void *dto, uint32_t delta)
> +{
> +       int fixups;
> +
> +       fixups = fdt_path_offset(dto, "/__local_fixups__");
> +       if (fixups < 0) {
> +               /*
> +                * There's no local phandles to adjust, bail out

On on line:

/* There's not local ... */

> +                */
> +               if (fixups == -FDT_ERR_NOTFOUND)
> +                       return 0;
> +
> +               return fixups;
> +       }
> +
> +       /*
> +        * Update our local references from the root of the tree
> +        */
> +       return overlay_update_local_node_references(dto, 0, fixups,
> +                                                   delta);
> +}
> +
> +static int overlay_fixup_one_phandle(void *fdt, void *fdto,
> +                                    int symbols_off,
> +                                    const char *path, uint32_t path_len,
> +                                    const char *name, uint32_t name_len,
> +                                    int index, const char *label)
> +{
> +       const char *symbol_path;
> +       uint32_t phandle;
> +       int symbol_off, fixup_off;
> +       int prop_len;
> +
> +       symbol_path = fdt_getprop(fdt, symbols_off, label,
> +                                 &prop_len);
> +       if (!symbol_path)
> +               return -FDT_ERR_NOTFOUND;
> +
> +       symbol_off = fdt_path_offset(fdt, symbol_path);
> +       if (symbol_off < 0)
> +               return symbol_off;
> +
> +       phandle = fdt_get_phandle(fdt, symbol_off);
> +       if (!phandle)
> +               return -FDT_ERR_NOTFOUND;
> +
> +       fixup_off = fdt_path_offset_namelen(fdto, path, path_len);
> +       if (fixup_off < 0)
> +               return fixup_off;
> +
> +       phandle = cpu_to_fdt32(phandle);
> +       return fdt_setprop_inplace_namelen_by_index(fdto, fixup_off,
> +                                                   name, name_len, index,
> +                                                   &phandle, sizeof(phandle));
> +};
> +
> +static int overlay_fixup_phandle(void *fdt, void *fdto, int symbols_off,
> +                                int property)
> +{
> +       const char *value;
> +       const char *label;
> +       int len;
> +
> +       value = fdt_getprop_by_offset(fdto, property,
> +                                     &label, &len);
> +       if (!value)
> +               return len;
> +
> +       do {
> +               const char *prop_string = value;
> +               const char *path, *name;
> +               uint32_t path_len, name_len;
> +               char *sep, *endptr;
> +               int index;
> +               int ret;
> +
> +               path = prop_string;
> +               sep = strchr(prop_string, ':');
> +               path_len = sep - path;
> +
> +               name = sep + 1;
> +               sep = strchr(name, ':');
> +               name_len = sep - name;
> +
> +               index = strtoul(sep + 1, &endptr, 10);
> +               if (endptr <= (sep + 1))
> +                       return -FDT_ERR_BADSTRUCTURE;
> +
> +               index = strtoul(sep + 1, &endptr, 10);
> +               if (endptr <= (sep + 1))
> +                       return -FDT_ERR_BADSTRUCTURE;
> +
> +               len -= strlen(prop_string) + 1;
> +               value += strlen(prop_string) + 1;
> +
> +               ret = overlay_fixup_one_phandle(fdt, fdto, symbols_off,
> +                                               path, path_len, name, name_len,
> +                                               index, label);
> +               if (ret)
> +                       return ret;
> +       } while (len > 0);
> +
> +       return 0;
> +}
> +
> +static int overlay_fixup_phandles(void *dt, void *dto)
> +{
> +       int fixups_off, symbols_off;
> +       int property;
> +
> +       symbols_off = fdt_path_offset(dt, "/__symbols__");
> +       fixups_off = fdt_path_offset(dto, "/__fixups__");
> +
> +       fdt_for_each_property_offset(property, dto, fixups_off)
> +               overlay_fixup_phandle(dt, dto, symbols_off, property);
> +
> +       return 0;
> +}
> +
> +static int apply_overlay_node(void *dt, int target,
> +                             void *dto, int overlay)
> +{
> +       int property;
> +       int node;
> +
> +       fdt_for_each_property_offset(property, dto, overlay) {
> +               const char *name;
> +               const void *prop;
> +               int prop_len;
> +               int ret;
> +
> +               prop = fdt_getprop_by_offset(dto, property, &name,
> +                                            &prop_len);
> +               if (!prop)
> +                       return -FDT_ERR_INTERNAL;
> +
> +               ret = fdt_setprop(dt, target, name, prop, prop_len);
> +               if (ret)
> +                       return ret;
> +       }
> +
> +       fdt_for_each_subnode(dto, node, overlay) {
> +               const char *name = fdt_get_name(dto, node, NULL);
> +               int nnode;
> +               int ret;
> +
> +               nnode = fdt_add_subnode(dt, target, name);
> +               if (nnode == -FDT_ERR_EXISTS)
> +                       nnode = fdt_subnode_offset(dt, target, name);
> +
> +               if (nnode < 0)
> +                       return nnode;
> +
> +               ret = apply_overlay_node(dt, nnode, dto, node);
> +               if (ret)
> +                       return ret;
> +       }
> +
> +       return 0;
> +}
> +
> +static int overlay_merge(void *dt, void *dto)
> +{
> +       int fragment;
> +
> +       fdt_for_each_subnode(dto, fragment, 0) {
> +               int overlay;
> +               int target;
> +               int ret;
> +
> +               target = overlay_get_target(dt, dto, fragment);
> +               if (target < 0)
> +                       continue;
> +
> +               overlay = fdt_subnode_offset(dto, fragment, "__overlay__");
> +               if (overlay < 0)
> +                       return overlay;
> +
> +               ret = apply_overlay_node(dt, target, dto, overlay);
> +               if (ret)
> +                       return ret;
> +       }
> +
> +       return 0;
> +}
> +
> +int fdt_overlay_apply(void *fdt, void *fdto)
> +{
> +       uint32_t delta = fdt_get_max_phandle(fdt) + 1;
> +       int ret;
> +
> +       FDT_CHECK_HEADER(fdt);
> +       FDT_CHECK_HEADER(fdto);
> +
> +       ret = overlay_adjust_local_phandles(fdto, delta);
> +       if (ret)
> +               goto err;
> +
> +       ret = overlay_update_local_references(fdto, delta);
> +       if (ret)
> +               goto err;
> +
> +       ret = overlay_fixup_phandles(fdt, fdto);
> +       if (ret)
> +               goto err;
> +
> +       ret = overlay_merge(fdt, fdto);
> +       if (!ret)
> +               goto out;
> +
> +err:
> +       /*
> +        * The base device tree might have been damaged, erase its
> +        * magic.
> +        */
> +       fdt_set_magic(fdt, ~0);
> +
> +out:
> +       /*
> +        * The overlay has been damaged, erase its magic.
> +        */
> +       fdt_set_magic(fdto, ~0);
> +
> +       return ret;
> +}
> --
> 2.9.0
>

Regards,
Simon