Hi Stephen,
On Mon, Nov 28, 2011 at 10:41 AM, Stephen Warren swarren@nvidia.com wrote:
On 11/23/2011 08:54 PM, Simon Glass wrote:
Add a function to lookup a property which is a phandle in a node, and another to read a fixed-length integer array from an fdt property. Also add a function to read boolean properties.
Signed-off-by: Simon Glass sjg@chromium.org
Looking at the U-Boot custodians web page, you need to send the core DT changes (well, probably anything DT related) to Jerry Van Baren.
Yes the tag was there but not picked up as I didn't have Mike's alias file in my tree. Will fix.
+/**
- Look up a property in a node and return its contents in an integer
- array of given length. The property must have at least enough data for
- the array (4*count bytes). It may have more, but this will be ignored.
- @param blob FDT blob
- @param node node to examine
- @param prop_name name of property to find
- @param array array to fill with data
- @param count number of array elements
- @return 0 if ok, or -FDT_ERR_NOTFOUND if the property is not found,
- or -FDT_ERR_BADLAYOUT if not enough data
- */
+int fdtdec_get_int_array(const void *blob, int node, const char *prop_name,
- int *array, int count);
The kernel's equivalent of this function retrieves an array of U32s. Is one version more correct than the other?
I would prefer to have signed, but I will change it to use u32 *.
+/**
- Look up a boolean property in a node and return it.
- A boolean properly is true if present in the device tree and false if not
- present, or present with a 0 value.
- @param blob FDT blob
- @param node node to examine
- @param prop_name name of property to find
- @return 1 if the properly is present; 0 if it isn't present or is 0
- */
+int fdtdec_get_bool(const void *blob, int node, const char *prop_name);
Does U-Boot allow use of the "bool" type here?
Which bool type? It is returning an int.
+/**
- Look up a property in a node and check that it has a minimum length.
- @param blob FDT blob
- @param node node to examine
- @param prop_name name of property to find
- @param min_len minimum property length in bytes
- @param err 0 if ok, or -FDT_ERR_NOTFOUND if the property is not
- found, or -FDT_ERR_BADLAYOUT if not enough data
- @return pointer to cell, which is only valid if err == 0
- */
+static const void *get_prop_len(const void *blob, int node,
- const char *prop_name, int min_len, int *err)
Based on the function name, I'd expect it to return the length of the property; perhaps get_prop_check_min_len?
Changed, thanks.
+/**
- Look up a boolean property in a node and return it.
- A boolean properly is true if present in the device tree and false if not
- present, or present with a 0 value.
- @param blob FDT blob
- @param node node to examine
- @param prop_name name of property to find
- @return 1 if the properly is present; 0 if it isn't present or is 0
- */
+int fdtdec_get_bool(const void *blob, int node, const char *prop_name) +{
- const s32 *cell;
- int len;
- debug("%s: %s\n", __func__, prop_name);
- cell = fdt_getprop(blob, node, prop_name, &len);
- if (!cell)
- return 0;
- if (len >= sizeof(u32) && *cell == 0)
- return 0;
- return 1;
+}
In the kernel, I believe that property existence is all that's usually checked. Is that wrong? Did the definition of a boolean property's value in the function description above come from the specification? If a property had a length of 0/1/2/3 with a zero value, it seems very odd to treat that as true.
It is useful to be able to set the value to 0 or 1 (with fdtget/put), rather than remove or add the property. A value with a length of less than one cell is considered illegal here.
The basic idea is that the presence of the property means that it is 'true'. If it happens to have a value, then we allow that to specify 'false' if it is zero.
Thoughts?
Regards, Simon
-- nvpublic