On 16/10/2020 14:31, Rob Herring wrote:
On Thu, Oct 15, 2020 at 11:52 AM Robin Murphy <robin.murphy@xxxxxxx> wrote:
On 2020-10-14 19:39, Rob Herring wrote:
On Wed, Oct 14, 2020 at 9:54 AM Richard Fitzgerald
<rf@xxxxxxxxxxxxxxxxxxxxx> wrote:
Add an equivalent of of_count_phandle_with_args() for fixed argument
sets, to pair with of_parse_phandle_with_fixed_args().
Signed-off-by: Richard Fitzgerald <rf@xxxxxxxxxxxxxxxxxxxxx>
---
drivers/of/base.c | 42 ++++++++++++++++++++++++++++++++++++++++++
include/linux/of.h | 9 +++++++++
2 files changed, 51 insertions(+)
diff --git a/drivers/of/base.c b/drivers/of/base.c
index ea44fea99813..45d8b0e65345 100644
--- a/drivers/of/base.c
+++ b/drivers/of/base.c
@@ -1772,6 +1772,48 @@ int of_count_phandle_with_args(const struct device_node *np, const char *list_na
}
EXPORT_SYMBOL(of_count_phandle_with_args);
+/**
+ * of_count_phandle_with_fixed_args() - Find the number of phandles references in a property
+ * @np: pointer to a device tree node containing a list
+ * @list_name: property name that contains a list
+ * @cell_count: number of argument cells following the phandle
+ *
+ * Returns the number of phandle + argument tuples within a property. It
+ * is a typical pattern to encode a list of phandle and variable
+ * arguments into a single property.
+ */
+int of_count_phandle_with_fixed_args(const struct device_node *np,
+ const char *list_name,
+ int cells_count)
+{
Looks to me like you can refactor of_count_phandle_with_args to handle
both case and then make this and of_count_phandle_with_args simple
wrapper functions.
Although for just counting the number of phandles each with n arguments
that a property contains, isn't that simply a case of dividing the
property length by n + 1? The phandles themselves will be validated by
any subsequent of_parse_phandle*() call anyway, so there doesn't seem
much point in doing more work then necessary here.
+ struct of_phandle_iterator it;
+ int rc, cur_index = 0;
+
+ if (!cells_count) {
+ const __be32 *list;
+ int size;
+
+ list = of_get_property(np, list_name, &size);
+ if (!list)
+ return -ENOENT;
+
+ return size / sizeof(*list);
Case in point - if it's OK to do exactly that for n == 0, then clearly
we're *aren't* fussed about validating anything, so the n > 0 code below
is nothing more than a massively expensive way to check for a nonzero
remainder :/
Indeed. We should just generalize this. It can still be refactored to
shared code.
It's probably worthwhile to check for a remainder here IMO.
Ok, I looked at the implementation of of_phandle_iterator_next() and
it is in fact simply incrementing by 'count' 32-bit words. So as Robin
said the count_phandle_with_x_args()functions could simply divide the
length by count+1.
However, may I suggest that should be done in a separate patch after my
patch to add count_phandle_with_fixed_args()? That way, if replacing the
iteration with the simple length divide causes any unforeseen problems
the patch can just be reverted.
Rob
