On 06/27/16 20:12, David Gibson wrote:
On Mon, Jun 27, 2016 at 01:40:00PM +0200, Maxime Ripard wrote:
Hi David,
On Mon, Jun 27, 2016 at 03:26:07PM +1000, David Gibson wrote:
+static uint32_t overlay_get_target_phandle(const void *fdto, int fragment) +{
- const uint32_t *val;
- int len;
- val = fdt_getprop(fdto, fragment, "target", &len);
- if (!val || (*val == 0xffffffff) || (len != sizeof(*val)))
return 0;This doesn't distinguish between a missing property (which may indicate a valid overlay using a target-path or some other method) and a badly formatted 'target' property, which is definitely an error in the overlay.
I think those should be treated differently.
AFAIK, phandles can have any 32 bits values but 0xffffffff. In order to cover the two cases, we would need to have some error code, but that doesn't really work with returning a uint32_t.
Actually phandles can have any value except 0xffffffff *or* 0. So you can use 0 for "couldn't find" and -1 for "badly formatted".
< snip >
Hi David,
I would like to capture this for the specification.
It seems like I could say that a value of 0 in the FDT is not allowed.
Then thinking of what Pantelis is doing with overlays, it seems like a value of 0xffffffff is allowed in the FDT, but it means not a valid phandle, so do not try to de-reference it.
Does that sound good?
-Frank