Hi Theirry,
On 19 August 2014 04:59, Thierry Reding thierry.reding@gmail.com wrote:
On Mon, Aug 18, 2014 at 11:52:36AM -0600, Simon Glass wrote:
Hi Thierry,
On 18 August 2014 01:16, Thierry Reding thierry.reding@gmail.com
wrote:
From: Thierry Reding treding@nvidia.com
Given a device tree node, the fdt_n_addr_cells() function will walk up the device tree and search for an #address-cells property. It returns the number of cells required by the device tree node to represent an address.
Similarly the fdt_n_size_cells() function returns the number of cells required by the given device tree node to represent a size. It achieves that by walking up the device tree in seach for a #size-cells property.
If no #address-cells or #size-cells property can be found, both of the functions return 1.
Signed-off-by: Thierry Reding treding@nvidia.com
include/libfdt.h | 28 ++++++++++++++++++++++++++++ lib/libfdt/fdt_ro.c | 36 ++++++++++++++++++++++++++++++++++++ 2 files changed, 64 insertions(+)
diff --git a/include/libfdt.h b/include/libfdt.h index a1ef1e15df3d..e7f991b388cf 100644 --- a/include/libfdt.h +++ b/include/libfdt.h @@ -1638,4 +1638,32 @@ int fdt_find_regions(const void *fdt, char *
const inc[], int inc_count,
struct fdt_region region[], int max_regions, char *path, int path_len, int add_string_tab);+/**
- fdt_n_addr_cells() - find the number of address cells required by
a node
- Looks up the #address-cells property of the node to examine. If
that has
- no such property, walks up the device tree until it finds one in
one of
- the device's parents. If no #address-cells property is found, it is
- assumed to be 1.
- @param fdt FDT blob
- @param node node to examine
- @return number of address cells
- */
+int fdt_n_addr_cells(const void *fdt, int node);
There is a new fdt_address_cells() recently that looks suitable.
+/**
- fdt_n_size_cells() - find the number of size cells required by a
node
Also fdt_size_cells().
Neither of those seem to walk up the tree, so inheriting #address-cells or #size-cells from a parent will not work.
According to the comments in the code they're also supposed to return the number of cells represented by a bus, not a device (which might explain why it doesn't walk up the tree).
I also can't reuse them to implement these fdt_n_addr_cells() and fdt_n_size_cells() functions because they don't return an accurate error if the #address-cells and #size-cells are not found, therefore it's impossible to decide when to climb further up the tree.
OK but I have one more question. I thought that dtc gave a warning when you don't explicitly specify these values in the parent node?
Regards, Simon