On Wed, Mar 14, 2018 at 02:41:03PM +0100, Mario Six wrote:
1;5002;0c> Given a node offset, the function fdt_get_phandle finds and returns the
> phandle property defined in this node.
>
> The current implementation first tries to read the "phandle" property,
> then, should this not succeed, tries to read the "linux,phandle" property
> afterwards (both by using the fdt_getprop function), and returns either
> one if it is found.
>
> This means that we potentially iterate over the properties of the node
> twice (if the neither the "phandle", nor the "linux,phandle" property is
> found).
>
> Instead of doing this, iterate once over the nodes' properties, and
> check each one if it is equal to either "phandle" or "linux,phandle",
> and return the value in either case. Hence, we only iterate over the
> properties exactly once.
>
> Signed-off-by: Mario Six <mario.six@xxxxxxxx>
Unless we have someone hitting performance problems in practice, I'm a
bit dubious as to whether the performance increase is worth the
increase in code complexity.
> ---
> libfdt/fdt_ro.c | 31 ++++++++++++++++++++++---------
> 1 file changed, 22 insertions(+), 9 deletions(-)
>
> diff --git a/libfdt/fdt_ro.c b/libfdt/fdt_ro.c
> index dfb3236..7d049fb 100644
> --- a/libfdt/fdt_ro.c
> +++ b/libfdt/fdt_ro.c
> @@ -424,19 +424,32 @@ const void *fdt_getprop(const void *fdt, int nodeoffset,
>
> uint32_t fdt_get_phandle(const void *fdt, int nodeoffset)
> {
> - const fdt32_t *php;
> + const fdt32_t *php = NULL;
> int len;
> + int offset;
>
> - /* FIXME: This is a bit sub-optimal, since we potentially scan
> - * over all the properties twice. */
> - php = fdt_getprop(fdt, nodeoffset, "phandle", &len);
> - if (!php || (len != sizeof(*php))) {
> - php = fdt_getprop(fdt, nodeoffset, "linux,phandle", &len);
> - if (!php || (len != sizeof(*php)))
> - return 0;
> + for (offset = fdt_first_property_offset(fdt, nodeoffset);
> + (offset >= 0);
> + (offset = fdt_next_property_offset(fdt, offset))) {
> + const struct fdt_property *prop;
> +
> + if (!(prop = fdt_get_property_by_offset(fdt, offset, &len))) {
> + offset = -FDT_ERR_INTERNAL;
> + break;
> + }
> + if (fdt_string_eq_(fdt, fdt32_to_cpu(prop->nameoff),
> + "phandle", strlen("phandle")))
> + php = (const fdt32_t *)prop->data;
> +
> + if (fdt_string_eq_(fdt, fdt32_to_cpu(prop->nameoff),
> + "linux,phandle", strlen("linux,phandle")))
> + php = (const fdt32_t *)prop->data;
> +
> + if (php)
> + return fdt32_to_cpu(*php);
> }
>
> - return fdt32_to_cpu(*php);
> + return 0;
> }
>
> const char *fdt_get_alias_namelen(const void *fdt,
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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