On Fri, Mar 01, 2024 at 02:04:43PM +0100, Ahmad Fatoum wrote:
> When finding compatible bootloader spec files, barebox will unflatten
> each DTB in turn, allocating objects for each property and node, only to
> compare a single property and then free all the allocations again.
>
> Given that this operation is repeated for every device tree until a
> match is found, it's a good idea to be able to compare machine
> (top-level) compatibles without having to unflatten the whole FDT.
>
> Implemnt fdt_machine_is_compatible() that does just that. This
> intentionally opencodes the device tree iteration as to minimize
> code and runtime size. Using libfdt without LTO would be slower
> and bigger.
>
> Signed-off-by: Ahmad Fatoum <a.fatoum@xxxxxxxxxxxxxx>
> ---
> drivers/of/fdt.c | 95 ++++++++++++++++++++++++++++++++++++++++++++++++
> include/of.h | 3 ++
> 2 files changed, 98 insertions(+)
>
> diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
> index 676b8a5535bf..aa3d2e967acd 100644
> --- a/drivers/of/fdt.c
> +++ b/drivers/of/fdt.c
> @@ -668,3 +668,98 @@ void fdt_print_reserve_map(const void *__fdt)
> return;
> }
> }
> +
> +static int fdt_string_is_compatible(const char *haystack, int haystack_len,
> + const char *needle, int needle_len)
> +{
> + const char *p;
> + int index = 0;
> +
> + while (haystack_len >= needle_len) {
> + if (memcmp(needle, haystack, needle_len + 1) == 0)
> + return OF_DEVICE_COMPATIBLE_MAX_SCORE - (index << 2);
> +
> + p = memchr(haystack, '\0', haystack_len);
> + if (!p)
> + return 0;
> + haystack_len -= (p - haystack) + 1;
> + haystack = p + 1;
> + index++;
> + }
> +
> + return 0;
> +}
> +
> +bool fdt_machine_is_compatible(const struct fdt_header *fdt, size_t fdt_size, const char *compat)
> +{
> + uint32_t tag;
> + const struct fdt_property *fdt_prop;
> + const char *name;
> + uint32_t dt_struct;
> + const struct fdt_node_header *fnh;
> + const void *dt_strings;
> + struct fdt_header f;
> + int ret, len;
> + int expect = FDT_BEGIN_NODE;
> + int compat_len = strlen(compat);
> +
> + ret = fdt_parse_header(fdt, fdt_size, &f);
> + if (ret < 0)
> + return ERR_PTR(ret);
return false here
Sascha
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