Re: [PATCH v4 09/14] of: reserved-memory: Fix using wrong number of cells to get property 'alignment'
From: Rob Herring <robh@kernel.org>
Date: 2025-01-13 23:25:52
Also in:
lkml, stable
On Thu, Jan 09, 2025 at 09:27:00PM +0800, Zijun Hu wrote:
From: Zijun Hu <redacted> According to DT spec, size of property 'alignment' is based on parent node’s #size-cells property. But __reserved_mem_alloc_size() wrongly uses @dt_root_addr_cells to get the property obviously. Fix by using @dt_root_size_cells instead of @dt_root_addr_cells.
I wonder if changing this might break someone. It's been this way for a long time. It might be better to change the spec or just read 'alignment' as whatever size it happens to be (len / 4). It's not really the kernel's job to validate the DT. We should first have some validation in place to *know* if there are any current .dts files that would break. That would probably be easier to implement in dtc than dtschema. Cases of #address-cells != #size-cells should be pretty rare, but that was the default for OpenFirmware. As the alignment is the base address alignment, it can be argued that "#address-cells" makes more sense to use than "#size-cells". So maybe the spec was a copy-n-paste error.
quoted hunk ↗ jump to hunk
Fixes: 3f0c82066448 ("drivers: of: add initialization code for dynamic reserved memory") Cc: stable@vger.kernel.org Signed-off-by: Zijun Hu <redacted> --- drivers/of/of_reserved_mem.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)diff --git a/drivers/of/of_reserved_mem.c b/drivers/of/of_reserved_mem.c index 45517b9e57b1add36bdf2109227ebbf7df631a66..d2753756d7c30adcbd52f57338e281c16d821488 100644 --- a/drivers/of/of_reserved_mem.c +++ b/drivers/of/of_reserved_mem.c@@ -409,12 +409,12 @@ static int __init __reserved_mem_alloc_size(unsigned long node, const char *unam prop = of_get_flat_dt_prop(node, "alignment", &len); if (prop) { - if (len != dt_root_addr_cells * sizeof(__be32)) { + if (len != dt_root_size_cells * sizeof(__be32)) { pr_err("invalid alignment property in '%s' node.\n", uname); return -EINVAL; } - align = dt_mem_next_cell(dt_root_addr_cells, &prop); + align = dt_mem_next_cell(dt_root_size_cells, &prop); } nomap = of_get_flat_dt_prop(node, "no-map", NULL) != NULL;-- 2.34.1