Re: [PATCH 09/23] pbl: fdt: add pbl_load_fdt helper

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

Hello Marco.

On 11/10/25 9:34 PM, Marco Felsch wrote:
> The helper provides a common FDT load mechanism to load the (compressed)
> DTB to the provided destination address. Early FDTs may required by
> other BL3x binaries like BL31 (TF-A) and BL32 (OP-TEE).
> 
> Signed-off-by: Marco Felsch <m.felsch@pengutronix.de>
> ---
>  arch/Kconfig  |  3 +++
>  include/pbl.h |  2 ++
>  pbl/Kconfig   | 11 +++++++++
>  pbl/fdt.c     | 75 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 91 insertions(+)
> 
> diff --git a/arch/Kconfig b/arch/Kconfig
> index 55618bf896c25f2afa2786706e27fce6ab4b3a39..edd574879b244d3843f1b5a06e1e25c5d4acbc8d 100644
> --- a/arch/Kconfig
> +++ b/arch/Kconfig
> @@ -62,6 +62,9 @@ config ARCH_DMA_DEFAULT_COHERENT
>  config ARCH_HAS_DMA_WRITE_COMBINE
>  	bool
>  
> +config ARCH_HAS_EARLY_FDT_SUPPORT
> +	bool
> +
>  config ARCH_HAS_ASAN_FIBER_API
>  	bool
>  
> diff --git a/include/pbl.h b/include/pbl.h
> index 9db4652e833bf5e82fd42a1cae19e94c4f2f868f..bf0c9e2ba29428361cb16a572295e66f20acdd82 100644
> --- a/include/pbl.h
> +++ b/include/pbl.h
> @@ -31,6 +31,8 @@ fdt_device_get_match_data(const void *fdt, const char *nodepath,
>  
>  int pbl_barebox_verify(const void *compressed_start, unsigned int len,
>  		       const void *hash, unsigned int hash_len);
> +int pbl_load_fdt(const void *fdt, void *dest, int destsize);
> +
>  #endif
>  
>  void __noreturn barebox_pbl_entry(ulong, ulong, void *);
> diff --git a/pbl/Kconfig b/pbl/Kconfig
> index cab9325d16e8625bcca10125b3281062abffedbc..ea2086f33ea405ecd7b00065eaf9874218152b3a 100644
> --- a/pbl/Kconfig
> +++ b/pbl/Kconfig
> @@ -65,6 +65,17 @@ config PBL_VERIFY_PIGGY
>  	depends on ARM || MIPS || RISCV
>  	bool "Verify barebox proper hash before decompression" if COMPILE_TEST
>  
> +config PBL_EARLY_FDT_LOAD
> +	bool "Enable early FDT loading"
> +	depends on ARCH_HAS_EARLY_FDT_SUPPORT
> +	select LIBFDT
> +	help
> +	  This enables the support to decompress and load the barebox builtin DTB
> +	  during the pbl (BL2) phase.
> +
> +	  This is useful for BL31 and BL32 firmwares which may use the DTB for
> +	  device configuration.

There are ARM terms, but this is the generic pbl/Kconfig. I should the
symbol here should have no prompt and instead should be selected by an
architecture specific symbol if and only if the functionality will
actually be used.

Thanks,
Ahmad

> +
>  config PBL_CLOCKSOURCE
>  	bool
>  
> diff --git a/pbl/fdt.c b/pbl/fdt.c
> index ac377446caeafb1beaeb211aa8bdec8767ae21fe..0cd9f5a0f11723e9f9b6848e8553da481b92f2be 100644
> --- a/pbl/fdt.c
> +++ b/pbl/fdt.c
> @@ -1,8 +1,10 @@
>  // SPDX-License-Identifier: GPL-2.0
> +#include <compressed-dtb.h>
>  #include <linux/libfdt.h>
>  #include <pbl.h>
>  #include <linux/printk.h>
>  #include <stdio.h>
> +#include <uncompress.h>
>  
>  static const __be32 *fdt_parse_reg(const __be32 *reg, uint32_t n,
>  				   uint64_t *val)
> @@ -185,3 +187,76 @@ const void *fdt_device_get_match_data(const void *fdt, const char *nodepath,
>  
>  	return NULL;
>  }
> +
> +static int pbl_open_dtbz_into(const void *fdt, void *buf, int bufsize)
> +{
> +	const struct barebox_boarddata_compressed_dtb *compressed_dtb;
> +	int ret;
> +
> +	if (!fdt_blob_can_be_decompressed(fdt)) {
> +		pr_warn("DTB can't be decompressed\n");
> +		return -EINVAL;
> +	}
> +
> +	compressed_dtb = fdt;
> +
> +	if (IS_ENABLED(CONFIG_IMAGE_COMPRESSION_NONE)) {
> +		ret = fdt_open_into(compressed_dtb->data, buf, bufsize);
> +		if (ret)
> +			pr_warn("Failed to open uncompressed DTB with %s\n",
> +				fdt_strerror(ret));
> +		return ret ? -EINVAL : 0;
> +	}
> +
> +	if (bufsize < compressed_dtb->datalen_uncompressed) {
> +		pr_warn("FDT buffer to small, min. %u bytes required\n",
> +			compressed_dtb->datalen_uncompressed);
> +		return -EINVAL;
> +	}
> +
> +	ret = pbl_dtbz_uncompress(buf, (void *)compressed_dtb->data,
> +				  compressed_dtb->datalen);
> +	if (ret) {
> +		pr_warn("Failed to uncompress DTB err=%d\n", ret);
> +		return ret;
> +	}
> +
> +	if (!blob_is_fdt(buf)) {
> +		pr_warn("Failed to determine FDT type for uncompressed DTB\n");
> +		return -EINVAL;
> +	}
> +
> +	/* Required to setup size data structures to allow runtime adaptions */
> +	ret = fdt_open_into(buf, buf, bufsize);
> +	if (ret)
> +		pr_warn("Failed to open decompressed DTB with %s\n", fdt_strerror(ret));
> +
> +	return ret ? -EINVAL : 0;
> +}
> +
> +int pbl_load_fdt(const void *fdt, void *dest, int destsize)
> +{
> +	int ret;
> +
> +	if (!IS_ENABLED(CONFIG_PBL_EARLY_FDT_LOAD))
> +		return -ENOTSUPP;
> +
> +	if (destsize == 0) {
> +		pr_warn("Skip early FDT load due to dest buffer size of 0-bytes\n");
> +		return -EINVAL;
> +	}
> +
> +	if (blob_is_fdt(fdt)) {
> +		ret = fdt_open_into(fdt, dest, destsize);
> +		if (ret)
> +			pr_warn("Failed to uncompressed DTB with %s\n",
> +				fdt_strerror(ret));
> +		return ret ? -EINVAL : 0;
> +	} else if (blob_is_compressed_fdt(fdt)) {
> +		return pbl_open_dtbz_into(fdt, dest, destsize);
> +	}
> +
> +	pr_warn("FDT detection failed\n");
> +
> +	return -EINVAL;
> +}
> 

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