On 26.06.2013, at 10:49, Peter Maydell wrote: > On 26 June 2013 00:38, David Gibson <da...@gibson.dropbear.id.au> wrote: >> On Mon, Jun 24, 2013 at 12:02:39PM +0100, Peter Maydell wrote: >>> On 24 June 2013 11:56, Alexander Graf <ag...@suse.de> wrote: >>>> This looks pretty complicated for something actually quite >>>> simple: All you want is to pass in a number of 64bit values, >>>> rather than 32bit ones, right? >>> >>> Nope. If the device tree blob says #address-cells is 1 >>> and #size-cells is 1, then I want to pass in values to >>> go in 32 bit cells. If it says #address-cells is 2 but >>> #size-cells is still 1, then I want to pass in a value >>> for a 64 bit cell then one for a 32 bit cell. If they're >>> both 2 then I want to pass in values for two 64 bit >>> cells. >> >> Hmm.. the property certainly needs to be constructed that way. But I >> think Alex's point is that you could make the arguments all 64-bit, >> and then truncate them in the generated property. > > Er, the arguments *are* all 64 bits and truncated > in the generated property: > + * @...: 0-terminated list of uint32_t number-of-cells, uint64_t value pairs > >> There's a bigger problem, though, that exists with both versions. In >> general people expect integer arguments like this not to care too much >> about the exact integer type, because it will be promoted to the right >> thing. Except with varargs it won't. So if you ever have a >> notionally 64-bit address that happens to fit in a 32-bit variable and >> you pass that it, this function will be broken. And the worst of it >> is, it'll work most of the time, until you happen to hit the wrong ABI >> and parameter combination :(. > > Do you have a suggested improvement to the API to avoid this?
I think it makes sense to make this API special-purpose for "reg". We currently have a generic "put any number of 32bit values into the property" function (qemu_devtree_setprop_cells). Can't we also just add a qemu_devtree_setprop_reg() that walks the tree downwards in search for #address-cells and #size-cells and assembles the correct reg property from a list of 64bit arguments? qemu_devtree_setprop_reg(fdt, "/foo/bar", region[0].offset, region[0].size, region[1].offset, region[1].size); Maybe we could even make it more generic to also cover "ranges". Alex
