From mboxrd@z Thu Jan 1 00:00:00 1970 From: Simon Glass Date: Tue, 19 Aug 2014 06:52:22 -0600 Subject: [U-Boot] [PATCH 01/23] fdt: Add functions to query a node's #address- and #size-cells In-Reply-To: <20140819105955.GA19515@ulmo> References: <1408346196-30419-1-git-send-email-thierry.reding@gmail.com> <1408346196-30419-2-git-send-email-thierry.reding@gmail.com> <20140819105955.GA19515@ulmo> Message-ID: List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: u-boot@lists.denx.de Hi Theirry, On 19 August 2014 04:59, Thierry Reding wrote: > On Mon, Aug 18, 2014 at 11:52:36AM -0600, Simon Glass wrote: > > Hi Thierry, > > > > On 18 August 2014 01:16, Thierry Reding > wrote: > > > From: Thierry Reding > > > > > > 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 > > > --- > > > 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