From 5a457750ec5b1916602da8f18565232916e9713e Mon Sep 17 00:00:00 2001 From: Thierry Reding Date: Tue, 26 Mar 2019 16:33:02 +0100 Subject: libfdt: Add phandle generation helper The new fdt_generate_phandle() function can be used to generate a new, unused phandle given a specific device tree blob. The implementation is somewhat naive in that it simply walks the entire device tree to find the highest phandle value and then returns a phandle value one higher than that. A more clever implementation might try to find holes in the current set of phandle values and fill them. But this implementation is relatively simple and works reliably. Also add a test that validates that phandles generated by this new API are indeed unique. Signed-off-by: Thierry Reding Message-Id: <20190326153302.17109-3-thierry.reding@gmail.com> Signed-off-by: David Gibson --- cpukit/dtc/libfdt/fdt_ro.c | 18 ++++++++++++++++++ cpukit/include/libfdt.h | 19 +++++++++++++++++++ 2 files changed, 37 insertions(+) (limited to 'cpukit') diff --git a/cpukit/dtc/libfdt/fdt_ro.c b/cpukit/dtc/libfdt/fdt_ro.c index 1d0335ee71..817ac39099 100644 --- a/cpukit/dtc/libfdt/fdt_ro.c +++ b/cpukit/dtc/libfdt/fdt_ro.c @@ -184,6 +184,24 @@ uint32_t fdt_get_max_phandle(const void *fdt) return phandle; } +int fdt_generate_phandle(const void *fdt, uint32_t *phandle) +{ + uint32_t max; + int err; + + err = fdt_find_max_phandle(fdt, &max); + if (err < 0) + return err; + + if (max == FDT_MAX_PHANDLE) + return -FDT_ERR_NOPHANDLES; + + if (phandle) + *phandle = max + 1; + + return 0; +} + static const struct fdt_reserve_entry *fdt_mem_rsv(const void *fdt, int n) { int offset = n * sizeof(struct fdt_reserve_entry); diff --git a/cpukit/include/libfdt.h b/cpukit/include/libfdt.h index e1498c3c21..39ff6d5d25 100644 --- a/cpukit/include/libfdt.h +++ b/cpukit/include/libfdt.h @@ -140,6 +140,10 @@ #define FDT_ERR_MAX 17 +/* constants */ +#define FDT_MAX_PHANDLE 0xfffffffe + /* Valid values for phandles range from 1 to 2^32-2. */ + /**********************************************************************/ /* Low-level functions (you probably don't need these) */ /**********************************************************************/ @@ -416,6 +420,21 @@ int fdt_find_max_phandle(const void *fdt, uint32_t *phandle); */ uint32_t fdt_get_max_phandle(const void *fdt); +/** + * fdt_generate_phandle - return a new, unused phandle for a device tree blob + * @fdt: pointer to the device tree blob + * @phandle: return location for the new phandle + * + * Walks the device tree blob and looks for the highest phandle value. On + * success, the new, unused phandle value (one higher than the previously + * highest phandle value in the device tree blob) will be returned in the + * @phandle parameter. + * + * Returns: + * 0 on success or a negative error-code on failure + */ +int fdt_generate_phandle(const void *fdt, uint32_t *phandle); + /** * fdt_num_mem_rsv - retrieve the number of memory reserve map entries * @fdt: pointer to the device tree blob -- cgit v1.2.3