Dynamic cfg: Introduce fdt wrappers

Change-Id: I9b1cdaf2430a1998a69aa366ea1461224a3d43dc
Co-Authoured-by: Jeenu Viswambharan <Jeenu.Viswambharan@arm.com>
Signed-off-by: Soby Mathew <soby.mathew@arm.com>

diff --git a/common/fdt_wrappers.c b/common/fdt_wrappers.c
new file mode 100644 (file)
index 0000000..3766019
--- /dev/null
+++ b/common/fdt_wrappers.c
@@ -0,0 +1,96 @@
+/*
+ * Copyright (c) 2018, ARM Limited and Contributors. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+/* Helper functions to offer easier navigation of Device Tree Blob */
+
+#include <assert.h>
+#include <debug.h>
+#include <fdt_wrappers.h>
+#include <libfdt.h>
+
+/*
+ * Read cells from a given property of the given node. At most 2 cells of the
+ * property are read, and pointer is updated. Returns 0 on success, and -1 upon
+ * error
+ */
+int fdtw_read_cells(const void *dtb, int node, const char *prop,
+               unsigned int cells, void *value)
+{
+       const uint32_t *value_ptr;
+       uint32_t hi = 0, lo;
+       int value_len;
+
+       assert(dtb);
+       assert(prop);
+       assert(value);
+       assert(node >= 0);
+
+       /* We expect either 1 or 2 cell property */
+       assert(cells <= 2);
+
+       /* Access property and obtain its length (in bytes) */
+       value_ptr = fdt_getprop_namelen(dtb, node, prop, strlen(prop),
+                       &value_len);
+       if (value_ptr == NULL) {
+               WARN("Couldn't find property %s in dtb\n", prop);
+               return -1;
+       }
+
+
+       /* Verify that property length accords with cell length */
+       if (NCELLS(value_len) != cells) {
+               WARN("Property length mismatch\n");
+               return -1;
+       }
+
+       if (cells == 2) {
+               hi = fdt32_to_cpu(*value_ptr);
+               value_ptr++;
+       }
+
+       lo = fdt32_to_cpu(*value_ptr);
+
+       if (cells == 2)
+               *((uint64_t *) value) = ((uint64_t) hi << 32) | lo;
+       else
+               *((uint32_t *) value) = lo;
+
+       return 0;
+}
+
+/*
+ * Write cells in place to a given property of the given node. At most 2 cells
+ * of the property are written. Returns 0 on success, and -1 upon error.
+ */
+int fdtw_write_inplace_cells(void *dtb, int node, const char *prop,
+               unsigned int cells, void *value)
+{
+       int err, len;
+
+       assert(dtb);
+       assert(prop);
+       assert(value);
+       assert(node >= 0);
+
+       /* We expect either 1 or 2 cell property */
+       assert(cells <= 2);
+
+       if (cells == 2)
+               *(uint64_t *)value = cpu_to_fdt64(*(uint64_t *)value);
+       else
+               *(uint32_t *)value = cpu_to_fdt32(*(uint32_t *)value);
+
+       len = cells * 4;
+
+       /* Set property value in place */
+       err = fdt_setprop_inplace(dtb, node, prop, value, len);
+       if (err != 0) {
+               WARN("Modify property %s failed with error %d\n", prop, err);
+               return -1;
+       }
+
+       return 0;
+}

diff --git a/include/common/fdt_wrappers.h b/include/common/fdt_wrappers.h
new file mode 100644 (file)
index 0000000..db72f18
--- /dev/null
+++ b/include/common/fdt_wrappers.h
@@ -0,0 +1,19 @@
+/*
+ * Copyright (c) 2018, ARM Limited and Contributors. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+/* Helper functions to offer easier navigation of Device Tree Blob */
+
+#ifndef __FDT_WRAPPERS__
+#define __FDT_WRAPPERS__
+
+/* Number of cells, given total length in bytes. Each cell is 4 bytes long */
+#define NCELLS(l) (l / 4)
+
+int fdtw_read_cells(const void *dtb, int node, const char *prop,
+               unsigned int cells, void *value);
+int fdtw_write_inplace_cells(void *dtb, int node, const char *prop,
+               unsigned int cells, void *value);
+#endif /* __FDT_WRAPPERS__ */