linux-kernel - Re: [PATCH v2 5/7] of/fdt: Simplify the logic of early_init_dt_scan

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Message-ID: <20251113220356.GA800052-robh@kernel.org>
Date: Thu, 13 Nov 2025 16:03:56 -0600
From: Rob Herring <robh@...nel.org>
To: Yuntao Wang <yuntao.wang@...ux.dev>
Cc: Saravana Kannan <saravanak@...gle.com>,
	Geert Uytterhoeven <geert+renesas@...der.be>,
	Catalin Marinas <catalin.marinas@....com>,
	James Morse <james.morse@....com>, Baoquan He <bhe@...hat.com>,
	Zhen Lei <thunder.leizhen@...wei.com>,
	Ard Biesheuvel <ardb@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Geoff Levand <geoff@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Changyuan Lyu <changyuanl@...gle.com>,
	Alexander Graf <graf@...zon.com>,
	"Mike Rapoport (Microsoft)" <rppt@...nel.org>,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 5/7] of/fdt: Simplify the logic of
 early_init_dt_scan_memory()

On Thu, Nov 13, 2025 at 11:51:02PM +0800, Yuntao Wang wrote:
> Use the existing helper functions to simplify the logic of
> early_init_dt_scan_memory()
> 
> Signed-off-by: Yuntao Wang <yuntao.wang@...ux.dev>
> ---
>  drivers/of/fdt.c | 14 ++++++--------
>  1 file changed, 6 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
> index 4c45a97d6652..b6b059960fc2 100644
> --- a/drivers/of/fdt.c
> +++ b/drivers/of/fdt.c
> @@ -1027,7 +1027,7 @@ int __init early_init_dt_scan_memory(void)
>  
>  	fdt_for_each_subnode(node, fdt, 0) {
>  		const char *type = of_get_flat_dt_prop(node, "device_type", NULL);
> -		const __be32 *reg, *endp;
> +		const __be32 *reg;
>  		int l;
>  		bool hotpluggable;
>  
> @@ -1038,23 +1038,21 @@ int __init early_init_dt_scan_memory(void)
>  		if (!of_fdt_device_is_available(fdt, node))
>  			continue;
>  
> -		reg = of_get_flat_dt_prop(node, "linux,usable-memory", &l);
> +		reg = of_fdt_get_addr_size_prop(node, "linux,usable-memory", &l);
>  		if (reg == NULL)
> -			reg = of_get_flat_dt_prop(node, "reg", &l);
> +			reg = of_fdt_get_addr_size_prop(node, "reg", &l);
>  		if (reg == NULL)
>  			continue;
>  
> -		endp = reg + (l / sizeof(__be32));
>  		hotpluggable = of_get_flat_dt_prop(node, "hotpluggable", NULL);
>  
> -		pr_debug("memory scan node %s, reg size %d,\n",
> +		pr_debug("memory scan node %s, reg {addr,size} entries %d,\n",
>  			 fdt_get_name(fdt, node, NULL), l);
>  
> -		while ((endp - reg) >= (dt_root_addr_cells + dt_root_size_cells)) {
> +		while (l-- > 0) {
>  			u64 base, size;
>  
> -			base = dt_mem_next_cell(dt_root_addr_cells, &reg);
> -			size = dt_mem_next_cell(dt_root_size_cells, &reg);
> +			of_fdt_read_addr_size(reg, &base, &size);

This doesn't work. of_fdt_read_addr_size() needs to take an entry index 
to read each entry.

Rob