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libfdt: Add new maximum phandle lookup function

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The fdt_get_max_phandle() function has some shortcomings. On one hand
it returns just a uint32_t which means to check for the "negative"
error code a caller has to explicitly check against the error code
(uint32_t)-1. In addition, the -1 is the only error code that can be
returned, so a caller cannot tell the difference between the various
failures.

Fix this by adding a new fdt_find_max_phandle() function that returns an
error code on failure and 0 on success, just like other APIs, and stores
the maximum phandle value in an output argument on success.

This also refactors fdt_get_max_phandle() to use the new function. Add a
note pointing out that the new fdt_find_max_phandle() function should be
preferred over fdt_get_max_phandle().

Signed-off-by: Thierry Reding <treding@nvidia.com>
Message-Id: <20190326153302.17109-1-thierry.reding@gmail.com>
[dwg: Reword for some inaccuracies in the commit message]
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
This commit is contained in:
Thierry Reding 2019-03-26 16:33:00 +01:00 • committed by David Gibson
parent 7fcf8208b8
commit 2bc5b66d7f
5 changed files with 56 additions and 15 deletions
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16
libfdt/libfdt.h
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@ -385,6 +385,20 @@ const char *fdt_get_string(const void *fdt, int stroffset, int *lenp);
*/
const char *fdt_string(const void *fdt, int stroffset);
/**
* fdt_find_max_phandle - find and return the highest phandle in a tree
* @fdt: pointer to the device tree blob
* @phandle: return location for the highest phandle value found in the tree
*
* fdt_find_max_phandle() finds the highest phandle value in the given device
* tree. The value returned in @phandle is only valid if the function returns
* success.
*
* returns:
* 0 on success or a negative error code on failure
*/
int fdt_find_max_phandle(const void *fdt, uint32_t *phandle);
/**
* fdt_get_max_phandle - retrieves the highest phandle in a tree
* @fdt: pointer to the device tree blob
@ -393,6 +407,8 @@ const char *fdt_string(const void *fdt, int stroffset);
* device tree. This will ignore badly formatted phandles, or phandles
* with a value of 0 or -1.
*
* This function is deprecated in favour of fdt_find_max_phandle().
*
* returns:
* the highest phandle on success
* 0, if no phandle was found in the device tree