From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-189.mta1.migadu.com (out-189.mta1.migadu.com [95.215.58.189]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C1D3A4A32 for ; Sat, 15 Nov 2025 14:00:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.189 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763215261; cv=none; b=B/BvaJOt1eUEZC2GOBxW31T6DIMl4e1P+BxdLAKucHmeOV8je28PlkN4R+iaTPbnDNqcjwgD14PZiFZgz8URtrk8uGhx6+csoKtAmtVMoKOcUdRc784d5BuIf5x6oMtA6UOuP9QZLuDgvNqF9x36u420CIpvjD9B1c6tJvU5VW8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763215261; c=relaxed/simple; bh=Mi4i20cJqJ+Z/8j60CbnLDSsEpv52/KcengAD46mkE8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=akmJkoeauXlmgh81keVtj07aV5VzUGW6WZU+rsSvhMBYO7rtQhKFO3eB+QsAJ0iVprcnm9+jZwvuAG87U61awTjllAB+WwYm6JPD8UqlNLeC19V0FqpDyVD89ubWbdBJ+/ojnyIjqnp3nJ0MCLmOJTvfyU7xn0wq3NaFzaswJic= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=toEOUAPg; arc=none smtp.client-ip=95.215.58.189 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="toEOUAPg" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1763215256; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=z8NMA0mm1b2tQxBqcSqu3zbhpnWadSHLFLH6HP4EMl8=; b=toEOUAPg5P0R9SGVoKj8VFCmhxC0E7WPdGKVFH6w1VAv1CsDxH7gvYbPxEoUbMzV+0uhzV RzpQZlS2eCKC8328tpyhkP2BYZGt8prExGPAY1FSTs6X0TuJFXZhRbiFIR/163esP0Ms5B l/CD52as2U0eoJt+QgQputctWKBE/Sc= From: Yuntao Wang To: robh@kernel.org Cc: akpm@linux-foundation.org, ardb@kernel.org, bhe@redhat.com, catalin.marinas@arm.com, changyuanl@google.com, devicetree@vger.kernel.org, geert+renesas@glider.be, geoff@infradead.org, graf@amazon.com, james.morse@arm.com, linux-kernel@vger.kernel.org, mark.rutland@arm.com, rppt@kernel.org, saravanak@google.com, thunder.leizhen@huawei.com, yuntao.wang@linux.dev Subject: Re: [PATCH v2 5/7] of/fdt: Simplify the logic of early_init_dt_scan_memory() Date: Sat, 15 Nov 2025 22:00:29 +0800 Message-ID: <20251115140031.181716-1-yuntao.wang@linux.dev> In-Reply-To: References: Precedence: bulk X-Mailing-List: devicetree@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT On Fri, 14 Nov 2025 09:11:18 -0600, Rob Herring wrote: > On Thu, Nov 13, 2025 at 9:56 PM Yuntao Wang wrote: > > > > On Thu, 13 Nov 2025 16:03:56 -0600, Rob Herring wrote: > > > > > 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 > > > > --- > > > > 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, ®); > > > > - size = dt_mem_next_cell(dt_root_size_cells, ®); > > > > + 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 > > > > Hi Rob, > > > > This was entirely my mistake. I intended to pass ® rather than reg, > > just like how dt_mem_next_cell() works. > > > > So the correct definition of of_fdt_read_addr_size() should be: > > > > void __init of_fdt_read_addr_size(const __be32 **prop, u64 *addr, u64 *size); > > > > And the correct usage should be: > > > > of_fdt_read_addr_size(®, &base, &size); > > > > This bug was caused by my oversight — apologies for that. > > > > I didn’t choose an interface like `of_fdt_read_addr_size(reg, i, &base, &size)` > > because in normal cases the data in prop is consumed sequentially, and I felt > > there was no need to introduce an entry index parameter, which would increase > > the API’s complexity. > > Yes, but giving the index mirrors how the unflattened of_property APIs > work. Not so much with the FDT, but we're trying to eliminate giving > out raw pointers (with no lifetime) to the DT data. That doesn't work > well with overlays and dynamic DTs. > > > There is another issue reported by kernel test robot: > > > > drivers/of/fdt.c:903:31: error: incompatible pointer types passing 'phys_addr_t *' (aka 'unsigned int *') to parameter of type 'u64 *' (aka 'unsigned long long *') [-Wincompatible-pointer-types] > > > > Given this, the problem exists regardless of which implementation we choose. > > > > I’m considering two possible solutions: > > > > 1. Convert of_fdt_read_addr_size() into a macro. > > 2. Split it into two functions: of_fdt_read_addr() and of_fdt_read_size(). > > > > I’m leaning toward the second option. > > > > What do you think? Or do you have a better approach? > > Just use local u64 variables and then assign the values to the struct. > This will not warn: > > a_phys_addr = a_u64; > > (It could silently truncate values, but I'm pretty sure no one runs > 32-bit LPAE systems with a non-LPAE kernel on the very few systems > that even still exist). > > Rob Hi Rob, The link to the v3 patch series: https://lore.kernel.org/linux-devicetree/20251115134753.179931-1-yuntao.wang@linux.dev/ Thanks, Yuntao