[PATCH v14 06/16] of/fdt: add helper functions for handling properties

On 09/09/18 19:38, AKASHI Takahiro wrote:

Frank,

Thank you for the comments. I will address all of them, but
have one question:

On Fri, Sep 07, 2018 at 12:53:58PM -0700, Frank Rowand wrote:

quoted

On 09/07/18 01:00, AKASHI Takahiro wrote:

quoted

These functions will be used later to handle kexec-specific properties
in arm64's kexec_file implementation.

Signed-off-by: AKASHI Takahiro <redacted>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: Frank Rowand <redacted>
---
 drivers/of/fdt.c       | 62 ++++++++++++++++++++++++++++++++++++++++--
 include/linux/of_fdt.h | 10 +++++--
 2 files changed, 68 insertions(+), 4 deletions(-)

diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
index 800ad252cf9c..dc960cea1355 100644
--- a/drivers/of/fdt.c
+++ b/drivers/of/fdt.c

@@ -25,6 +25,7 @@
 #include <linux/debugfs.h>
 #include <linux/serial_core.h>
 #include <linux/sysfs.h>
+#include <linux/types.h>
 
 #include <asm/setup.h>  /* for COMMAND_LINE_SIZE */
 #include <asm/page.h>

@@ -537,8 +538,8 @@ void *of_fdt_unflatten_tree(const unsigned long *blob,
 EXPORT_SYMBOL_GPL(of_fdt_unflatten_tree);
 
 /* Everything below here references initial_boot_params directly. */
-int __initdata dt_root_addr_cells;
-int __initdata dt_root_size_cells;
+int dt_root_addr_cells;
+int dt_root_size_cells;
 
 void *initial_boot_params;
 

@@ -1323,3 +1324,60 @@ late_initcall(of_fdt_raw_init);
 #endif
 
 #endif /* CONFIG_OF_EARLY_FLATTREE */
+

Please add comment:

/* helper functions for arm64 kexec */

quoted

+bool of_fdt_cells_size_fitted(u64 base, u64 size)

Please rename as of_fdt_range_valid()

quoted

+{
+	/* if *_cells >= 2, cells can hold 64-bit values anyway */
+	if ((dt_root_addr_cells == 1) && (base > U32_MAX))
+		return false;
+
+	if ((dt_root_size_cells == 1) && (size > U32_MAX))
+		return false;

Should also check that base + size does not wrap around.

What is the upper limit here?
For instance, #address_cells = <1> and #size_cells = <1>,
and can 'base + size' be over U32_MAX?
Assuming 'not' is quite reasonable, but it seems to me
that devicetree spec doesn't exclude it, as least I couldn't
find any notes about such a case.
(In my understands, #address_cells only restricts a size in 'reg' property.)

(See my other reply in this thread a few minutes ago -- the context of the
ranges is essentially what is valid for the "reg" property of the "/memory"
nodes.)

The "Devicetree Specification" does not specify whether a memory range can
wrap around.  For example, can a region of size 0x2000 that wraps around
the highest 32 bit address be specified as:

   / memory at 0xfffff000 {
        reg = <0xfffff000 0x2000>;
     }

or must it be specified as (option 1):

   / memory at 0xfffff000 {
        reg = <0xfffff000 0x1000 0x0 0x1000>
     }

or (option 2):

   / memory at 0xfffff000 {
        reg = <0xfffff000 0x1000>;
     }
     memory at 0 {
        reg = <0x0 0x1000>;
     }


I suggest you start a thread on the devicetree specification list asking
that the spec be updated to state whether wrap around is allowed.

Thanks,
-Takahiro Akashi

quoted

quoted

+
+	return true;
+}
+
+size_t of_fdt_reg_cells_size(void)

Please rename as of_fdt_root_range_size()

quoted

+{
+	return (dt_root_addr_cells + dt_root_size_cells) * sizeof(u32);
+}
+
+#define FDT_ALIGN(x, a)	(((x) + (a) - 1) & ~((a) - 1))
+#define FDT_TAGALIGN(x)	(FDT_ALIGN((x), FDT_TAGSIZE))
+
+int fdt_prop_len(const char *prop_name, int len)

Please rename as fdt_len_added_prop()

quoted

+{
+	return (strlen(prop_name) + 1) +
+		sizeof(struct fdt_property) +
+		FDT_TAGALIGN(len);
+}
+

Please add comment, something like:

/* cells must be 1 or 2 */

quoted

+static void fill_property(void *buf, u64 val64, int cells)

Please rename as cpu64_to_fdt_cells()

Thanks,

Frank

quoted

+{
+	__be32 val32;
+
+	while (cells) {
+		val32 = cpu_to_fdt32((val64 >> (32 * (--cells))) & U32_MAX);
+		memcpy(buf, &val32, sizeof(val32));
+		buf += sizeof(val32);
+	}
+}
+
+int fdt_setprop_reg(void *fdt, int nodeoffset, const char *name,
+						u64 addr, u64 size)
+{
+	char buf[sizeof(__be32) * 2 * 2];
+		/* assume dt_root_[addr|size]_cells <= 2 */
+	void *prop;
+	size_t buf_size;
+
+	buf_size = of_fdt_reg_cells_size();
+	prop = buf;
+
+	fill_property(prop, addr, dt_root_addr_cells);
+	prop += dt_root_addr_cells * sizeof(u32);
+
+	fill_property(prop, size, dt_root_size_cells);
+
+	return fdt_setprop(fdt, nodeoffset, name, buf, buf_size);
+}

diff --git a/include/linux/of_fdt.h b/include/linux/of_fdt.h
index b9cd9ebdf9b9..9615d6142578 100644
--- a/include/linux/of_fdt.h
+++ b/include/linux/of_fdt.h

@@ -37,8 +37,8 @@ extern void *of_fdt_unflatten_tree(const unsigned long *blob,
 				   struct device_node **mynodes);
 
 /* TBD: Temporary export of fdt globals - remove when code fully merged */
-extern int __initdata dt_root_addr_cells;
-extern int __initdata dt_root_size_cells;
+extern int dt_root_addr_cells;
+extern int dt_root_size_cells;
 extern void *initial_boot_params;
 
 extern char __dtb_start[];

@@ -108,5 +108,11 @@ static inline void unflatten_device_tree(void) {}
 static inline void unflatten_and_copy_device_tree(void) {}
 #endif /* CONFIG_OF_EARLY_FLATTREE */
 
+bool of_fdt_cells_size_fitted(u64 base, u64 size);
+size_t of_fdt_reg_cells_size(void);
+int fdt_prop_len(const char *prop_name, int len);
+int fdt_setprop_reg(void *fdt, int nodeoffset, const char *name,
+						u64 addr, u64 size);
+
 #endif /* __ASSEMBLY__ */
 #endif /* _LINUX_OF_FDT_H */