[PATCH] of: add function to count number of u32 elements in a property
From: mark.rutland@arm.com (Mark Rutland)
Date: 2014-01-17 14:45:37
Also in:
linux-devicetree, lkml
On Thu, Jan 16, 2014 at 06:04:42PM +0000, Heiko St?bner wrote:
The need to know the number of array elements in a property is a common pattern. To prevent duplication of open-coded implementations add a helper function that also centralises strict sanity checking and DTB format details. Suggested-by: Mark Rutland <mark.rutland@arm.com> Signed-off-by: Heiko Stuebner <heiko@sntech.de> --- Hi Mark, did you mean it like this? I've tested it with the sram-reserve change and it made the part of the determining the number elements a lot nicer :-)
Yes! This looks pretty nice! :)
quoted hunk ↗ jump to hunk
drivers/of/base.c | 32 ++++++++++++++++++++++++++++++++ include/linux/of.h | 8 ++++++++ 2 files changed, 40 insertions(+)diff --git a/drivers/of/base.c b/drivers/of/base.c index f807d0e..0f40ea5 100644 --- a/drivers/of/base.c +++ b/drivers/of/base.c@@ -920,6 +920,38 @@ int of_property_read_u32_index(const struct device_node *np, EXPORT_SYMBOL_GPL(of_property_read_u32_index); /** + * of_property_count_u32_elems - Count the number of u32 values in a property + * + * @np: device node from which the property value is to be read. + * @propname: name of the property to be searched. + * + * Search for a property in a device node and count the number of u32 elements + * in it. Returns number of elements on sucess, -EINVAL if the property does + * not exist or its length does not match a multiple of u32 and -ENODATA if the + * property does not have a value. + */ +int of_property_count_u32_elems(const struct device_node *np, + const char *propname) +{ + int elem_size = sizeof(u32); + int len; + struct property *prop = of_find_property(np, propname, &len); + + if (!prop) + return -EINVAL; + if (!prop->value) + return -ENODATA; + + if (prop->length % elem_size != 0) { + pr_err("size of %s is not a multiple of u32\n", propname); + return -EINVAL; + } + + return len / elem_size; +} +EXPORT_SYMBOL_GPL(of_property_count_u32_elems);
As Rob said in his reply, it would be nice to split this into a static
helper that took elem size as a parameter, so we can have the full suite
of of_property_count_{u8,u16,u32,u64}_elems.
Also, I think you can get rid of len and always use prop->length, as
other helpers seem to do.
Cheers for putting this together!
Mark.