On 2019-09-18 13:13, Rob Herring wrote:
On Wed, Sep 18, 2019 at 1:47 PM Raghavendra Rao Ananta
<rananta@xxxxxxxxxxxxxx> wrote:
On some embedded systems, the '/memory' dt-property gets updated
by the bootloader (for example, the DDR configuration) and then
gets passed onto the kernel. The device drivers may have to read
the properties at runtime to make decisions. Hence, add
of_get_memory_prop() for the device drivers to query the requested
Function name doesn't match. Device drivers don't need to access the
FDT.
properties.
Signed-off-by: Raghavendra Rao Ananta <rananta@xxxxxxxxxxxxxx>
---
drivers/of/fdt.c | 27 +++++++++++++++++++++++++++
include/linux/of_fdt.h | 1 +
2 files changed, 28 insertions(+)
We don't add kernel api's without users.
diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
index 223d617ecfe1..925cf2852433 100644
--- a/drivers/of/fdt.c
+++ b/drivers/of/fdt.c
@@ -79,6 +79,33 @@ void __init of_fdt_limit_memory(int limit)
}
}
+/**
+ * of_fdt_get_memory_prop - Return the requested property from the
/memory node
+ *
+ * On match, returns a non-zero positive value which represents the
property
+ * value. Otherwise returns -ENOENT.
+ */
+int of_fdt_get_memory_prop(const char *pname)
+{
+ int memory;
+ int len;
+ fdt32_t *prop = NULL;
+
+ if (!pname)
+ return -EINVAL;
+
+ memory = fdt_path_offset(initial_boot_params, "/memory");
Memory nodes should have a unit-address, so this won't work frequently.
Sorry, can you please elaborate more on this? What do you mean by
unit-address and working frequently?
+ if (memory > 0)
+ prop = fdt_getprop_w(initial_boot_params, memory,
+ pname, &len);
+
+ if (!prop || len != sizeof(u32))
+ return -ENOENT;
+
+ return fdt32_to_cpu(*prop);
+}
+EXPORT_SYMBOL_GPL(of_fdt_get_memory_prop);
+
static bool of_fdt_device_is_available(const void *blob, unsigned
long node)
{
const char *status = fdt_getprop(blob, node, "status", NULL);
diff --git a/include/linux/of_fdt.h b/include/linux/of_fdt.h
index acf820e88952..537f29373358 100644
--- a/include/linux/of_fdt.h
+++ b/include/linux/of_fdt.h
@@ -38,6 +38,7 @@ extern char __dtb_end[];
/* Other Prototypes */
extern u64 of_flat_dt_translate_address(unsigned long node);
extern void of_fdt_limit_memory(int limit);
+extern int of_fdt_get_memory_prop(const char *pname);
#endif /* CONFIG_OF_FLATTREE */
#ifdef CONFIG_OF_EARLY_FLATTREE
--
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Forum,
a Linux Foundation Collaborative Project
- Raghavendra
