new file mode 100644
@@ -0,0 +1,19 @@
+Broadcom bcm47xx/bcm53xx nvram access driver
+
+This driver provides access to the nvram for other drivers.
+
+Required properties:
+
+- compatible : brcm,bcm47xx-nvram
+
+- reg : iomem address range
+
+On NorthStar ARM SoCs the NAND flash is available at 0x1c000000 and the
+NOR flash is at 0x1e000000
+
+Example:
+
+nvram0: nvram@0 {
+ compatible = "brcm,bcm47xx-nvram";
+ reg = <0x1c000000 0x01000000>;
+};
@@ -218,36 +218,36 @@ static __init const struct bcm47xx_board_type *bcm47xx_board_get_nvram(void)
const struct bcm47xx_board_type_list2 *e2;
const struct bcm47xx_board_type_list3 *e3;
- if (bcm47xx_nvram_getenv("model_name", buf1, sizeof(buf1)) >= 0) {
+ if (bcm47xx_nvram_getenv(NULL, "model_name", buf1, sizeof(buf1)) >= 0) {
for (e1 = bcm47xx_board_list_model_name; e1->value1; e1++) {
if (!strcmp(buf1, e1->value1))
return &e1->board;
}
}
- if (bcm47xx_nvram_getenv("model_no", buf1, sizeof(buf1)) >= 0) {
+ if (bcm47xx_nvram_getenv(NULL, "model_no", buf1, sizeof(buf1)) >= 0) {
for (e1 = bcm47xx_board_list_model_no; e1->value1; e1++) {
if (strstarts(buf1, e1->value1))
return &e1->board;
}
}
- if (bcm47xx_nvram_getenv("machine_name", buf1, sizeof(buf1)) >= 0) {
+ if (bcm47xx_nvram_getenv(NULL, "machine_name", buf1, sizeof(buf1)) >= 0) {
for (e1 = bcm47xx_board_list_machine_name; e1->value1; e1++) {
if (strstarts(buf1, e1->value1))
return &e1->board;
}
}
- if (bcm47xx_nvram_getenv("hardware_version", buf1, sizeof(buf1)) >= 0) {
+ if (bcm47xx_nvram_getenv(NULL, "hardware_version", buf1, sizeof(buf1)) >= 0) {
for (e1 = bcm47xx_board_list_hardware_version; e1->value1; e1++) {
if (strstarts(buf1, e1->value1))
return &e1->board;
}
}
- if (bcm47xx_nvram_getenv("hardware_version", buf1, sizeof(buf1)) >= 0 &&
- bcm47xx_nvram_getenv("boardtype", buf2, sizeof(buf2)) >= 0) {
+ if (bcm47xx_nvram_getenv(NULL, "hardware_version", buf1, sizeof(buf1)) >= 0 &&
+ bcm47xx_nvram_getenv(NULL, "boardtype", buf2, sizeof(buf2)) >= 0) {
for (e2 = bcm47xx_board_list_boot_hw; e2->value1; e2++) {
if (!strstarts(buf1, e2->value1) &&
!strcmp(buf2, e2->value2))
@@ -255,22 +255,22 @@ static __init const struct bcm47xx_board_type *bcm47xx_board_get_nvram(void)
}
}
- if (bcm47xx_nvram_getenv("productid", buf1, sizeof(buf1)) >= 0) {
+ if (bcm47xx_nvram_getenv(NULL, "productid", buf1, sizeof(buf1)) >= 0) {
for (e1 = bcm47xx_board_list_productid; e1->value1; e1++) {
if (!strcmp(buf1, e1->value1))
return &e1->board;
}
}
- if (bcm47xx_nvram_getenv("ModelId", buf1, sizeof(buf1)) >= 0) {
+ if (bcm47xx_nvram_getenv(NULL, "ModelId", buf1, sizeof(buf1)) >= 0) {
for (e1 = bcm47xx_board_list_ModelId; e1->value1; e1++) {
if (!strcmp(buf1, e1->value1))
return &e1->board;
}
}
- if (bcm47xx_nvram_getenv("melco_id", buf1, sizeof(buf1)) >= 0 ||
- bcm47xx_nvram_getenv("buf1falo_id", buf1, sizeof(buf1)) >= 0) {
+ if (bcm47xx_nvram_getenv(NULL, "melco_id", buf1, sizeof(buf1)) >= 0 ||
+ bcm47xx_nvram_getenv(NULL, "buf1falo_id", buf1, sizeof(buf1)) >= 0) {
/* buffalo hardware, check id for specific hardware matches */
for (e1 = bcm47xx_board_list_melco_id; e1->value1; e1++) {
if (!strcmp(buf1, e1->value1))
@@ -278,8 +278,8 @@ static __init const struct bcm47xx_board_type *bcm47xx_board_get_nvram(void)
}
}
- if (bcm47xx_nvram_getenv("boot_hw_model", buf1, sizeof(buf1)) >= 0 &&
- bcm47xx_nvram_getenv("boot_hw_ver", buf2, sizeof(buf2)) >= 0) {
+ if (bcm47xx_nvram_getenv(NULL, "boot_hw_model", buf1, sizeof(buf1)) >= 0 &&
+ bcm47xx_nvram_getenv(NULL, "boot_hw_ver", buf2, sizeof(buf2)) >= 0) {
for (e2 = bcm47xx_board_list_boot_hw; e2->value1; e2++) {
if (!strcmp(buf1, e2->value1) &&
!strcmp(buf2, e2->value2))
@@ -287,16 +287,16 @@ static __init const struct bcm47xx_board_type *bcm47xx_board_get_nvram(void)
}
}
- if (bcm47xx_nvram_getenv("board_id", buf1, sizeof(buf1)) >= 0) {
+ if (bcm47xx_nvram_getenv(NULL, "board_id", buf1, sizeof(buf1)) >= 0) {
for (e1 = bcm47xx_board_list_board_id; e1->value1; e1++) {
if (!strcmp(buf1, e1->value1))
return &e1->board;
}
}
- if (bcm47xx_nvram_getenv("boardtype", buf1, sizeof(buf1)) >= 0 &&
- bcm47xx_nvram_getenv("boardnum", buf2, sizeof(buf2)) >= 0 &&
- bcm47xx_nvram_getenv("boardrev", buf3, sizeof(buf3)) >= 0) {
+ if (bcm47xx_nvram_getenv(NULL, "boardtype", buf1, sizeof(buf1)) >= 0 &&
+ bcm47xx_nvram_getenv(NULL, "boardnum", buf2, sizeof(buf2)) >= 0 &&
+ bcm47xx_nvram_getenv(NULL, "boardrev", buf3, sizeof(buf3)) >= 0) {
for (e3 = bcm47xx_board_list_board; e3->value1; e3++) {
if (!strcmp(buf1, e3->value1) &&
!strcmp(buf2, e3->value2) &&
@@ -305,9 +305,9 @@ static __init const struct bcm47xx_board_type *bcm47xx_board_get_nvram(void)
}
}
- if (bcm47xx_nvram_getenv("boardtype", buf1, sizeof(buf1)) >= 0 &&
- bcm47xx_nvram_getenv("boardrev", buf2, sizeof(buf2)) >= 0 &&
- bcm47xx_nvram_getenv("boardnum", buf3, sizeof(buf3)) == -ENOENT) {
+ if (bcm47xx_nvram_getenv(NULL, "boardtype", buf1, sizeof(buf1)) >= 0 &&
+ bcm47xx_nvram_getenv(NULL, "boardrev", buf2, sizeof(buf2)) >= 0 &&
+ bcm47xx_nvram_getenv(NULL, "boardnum", buf3, sizeof(buf3)) == -ENOENT) {
for (e2 = bcm47xx_board_list_board_type_rev; e2->value1; e2++) {
if (!strcmp(buf1, e2->value1) &&
!strcmp(buf2, e2->value2))
@@ -327,7 +327,7 @@ void __init bcm47xx_board_detect(void)
return;
/* check if the nvram is available */
- err = bcm47xx_nvram_getenv("boardtype", buf, sizeof(buf));
+ err = bcm47xx_nvram_getenv(NULL, "boardtype", buf, sizeof(buf));
/* init of nvram failed, probably too early now */
if (err == -ENXIO) {
@@ -158,7 +158,8 @@ static int nvram_init(void)
return -ENXIO;
}
-int bcm47xx_nvram_getenv(char *name, char *val, size_t val_len)
+int bcm47xx_nvram_getenv(const struct device *dev, const char *name, char *val,
+ size_t val_len)
{
char *var, *value, *end, *eq;
int err;
@@ -190,7 +191,7 @@ int bcm47xx_nvram_getenv(char *name, char *val, size_t val_len)
}
EXPORT_SYMBOL(bcm47xx_nvram_getenv);
-int bcm47xx_nvram_gpio_pin(const char *name)
+int bcm47xx_nvram_gpio_pin(const struct device *dev, const char *name)
{
int i, err;
char nvram_var[10];
@@ -200,7 +201,7 @@ int bcm47xx_nvram_gpio_pin(const char *name)
err = snprintf(nvram_var, sizeof(nvram_var), "gpio%i", i);
if (err <= 0)
continue;
- err = bcm47xx_nvram_getenv(nvram_var, buf, sizeof(buf));
+ err = bcm47xx_nvram_getenv(dev, nvram_var, buf, sizeof(buf));
if (err <= 0)
continue;
if (!strcmp(name, buf))
@@ -123,7 +123,7 @@ static int bcm47xx_get_invariants(struct ssb_bus *bus,
memset(&iv->sprom, 0, sizeof(struct ssb_sprom));
bcm47xx_fill_sprom(&iv->sprom, NULL, false);
- if (bcm47xx_nvram_getenv("cardbus", buf, sizeof(buf)) >= 0)
+ if (bcm47xx_nvram_getenv(NULL, "cardbus", buf, sizeof(buf)) >= 0)
iv->has_cardbus_slot = !!simple_strtoul(buf, NULL, 10);
return 0;
@@ -146,7 +146,7 @@ static void __init bcm47xx_register_ssb(void)
panic("Failed to initialize SSB bus (err %d)", err);
mcore = &bcm47xx_bus.ssb.mipscore;
- if (bcm47xx_nvram_getenv("kernel_args", buf, sizeof(buf)) >= 0) {
+ if (bcm47xx_nvram_getenv(NULL, "kernel_args", buf, sizeof(buf)) >= 0) {
if (strstr(buf, "console=ttyS1")) {
struct ssb_serial_port port;
@@ -52,10 +52,10 @@ static int get_nvram_var(const char *prefix, const char *postfix,
create_key(prefix, postfix, name, key, sizeof(key));
- err = bcm47xx_nvram_getenv(key, buf, len);
+ err = bcm47xx_nvram_getenv(NULL, key, buf, len);
if (fallback && err == -ENOENT && prefix) {
create_key(NULL, postfix, name, key, sizeof(key));
- err = bcm47xx_nvram_getenv(key, buf, len);
+ err = bcm47xx_nvram_getenv(NULL, key, buf, len);
}
return err;
}
@@ -61,7 +61,7 @@ void __init plat_time_init(void)
}
if (chip_id == 0x5354) {
- len = bcm47xx_nvram_getenv("clkfreq", buf, sizeof(buf));
+ len = bcm47xx_nvram_getenv(NULL, "clkfreq", buf, sizeof(buf));
if (len >= 0 && !strncmp(buf, "200", 4))
hz = 100000000;
}
@@ -515,6 +515,19 @@ config VEXPRESS_SYSCFG
bus. System Configuration interface is one of the possible means
of generating transactions on this bus.
+config BCM47XX_NVRAM
+ tristate "BCM47XX nvram driver"
+ depends on OF
+ help
+ This driver parses the nvram from a given memory range and
+ provides its values to other drivers.
+
+ The nvram is a key value store used on bcm47xx/bcm53xx SoC
+ with ARM and MIPS CPUs. It contains the board specific
+ configuration.
+
+ If unsure, say N.
+
source "drivers/misc/c2port/Kconfig"
source "drivers/misc/eeprom/Kconfig"
source "drivers/misc/cb710/Kconfig"
@@ -55,3 +55,4 @@ obj-y += mic/
obj-$(CONFIG_GENWQE) += genwqe/
obj-$(CONFIG_ECHO) += echo/
obj-$(CONFIG_VEXPRESS_SYSCFG) += vexpress-syscfg.o
+obj-$(CONFIG_BCM47XX_NVRAM) += bcm47xx-nvram.o
new file mode 100644
@@ -0,0 +1,215 @@
+/*
+ * BCM947xx nvram variable access
+ *
+ * Copyright (C) 2005 Broadcom Corporation
+ * Copyright (C) 2006 Felix Fietkau <nbd@openwrt.org>
+ * Copyright (C) 2010-2014 Hauke Mehrtens <hauke@hauke-m.de>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation; either version 2 of the License, or (at your
+ * option) any later version.
+ */
+
+#include <linux/types.h>
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/string.h>
+#include <linux/of_address.h>
+#include <linux/device.h>
+#include <linux/platform_device.h>
+#include <linux/io.h>
+#include <linux/bcm47xx_nvram.h>
+
+struct bcm47xx_nvram {
+ size_t nvram_len;
+ char *nvram_buf;
+};
+
+static const u32 nvram_sizes[] = {0x8000, 0xF000, 0x10000};
+
+static u32 find_nvram_size(void __iomem *end)
+{
+ struct nvram_header __iomem *header;
+ int i;
+
+ for (i = 0; i < ARRAY_SIZE(nvram_sizes); i++) {
+ header = (struct nvram_header __iomem *)(end - nvram_sizes[i]);
+ if (__raw_readl(&header->magic) == NVRAM_HEADER)
+ return nvram_sizes[i];
+ }
+
+ return 0;
+}
+
+/* Probe for NVRAM header */
+static int nvram_find_and_copy(struct device *dev, void __iomem *base,
+ size_t len, char **nvram_buf,
+ size_t *nvram_len)
+{
+ struct nvram_header __iomem *header;
+ int i;
+ u32 off;
+ u32 *dst;
+ __le32 __iomem *src;
+ u32 size;
+
+ /* TODO: when nvram is on nand flash check for bad blocks first. */
+ off = FLASH_MIN;
+ while (off <= len) {
+ /* Windowed flash access */
+ size = find_nvram_size(base + off);
+ if (size) {
+ header = (struct nvram_header __iomem *)
+ (base + off - size);
+ goto found;
+ }
+ off += 0x10000;
+ }
+
+ /* Try embedded NVRAM at 4 KB and 1 KB as last resorts */
+ header = (struct nvram_header __iomem *)(base + 4096);
+ if (__raw_readl(&header->magic) == NVRAM_HEADER) {
+ size = NVRAM_SPACE;
+ goto found;
+ }
+
+ header = (struct nvram_header __iomem *)(base + 1024);
+ if (__raw_readl(&header->magic) == NVRAM_HEADER) {
+ size = NVRAM_SPACE;
+ goto found;
+ }
+
+ *nvram_buf = NULL;
+ *nvram_len = 0;
+ pr_err("no nvram found\n");
+ return -ENXIO;
+
+found:
+ if (readl(&header->len) > size)
+ pr_err("The nvram size accoridng to the header seems to be bigger than the partition on flash\n");
+ *nvram_len = min_t(u32, readl(&header->len), size);
+
+ *nvram_buf = devm_kzalloc(dev, *nvram_len, GFP_KERNEL);
+ if (!*nvram_buf)
+ return -ENOMEM;
+
+ src = (__le32 __iomem *) header;
+ dst = (u32 *) *nvram_buf;
+ for (i = 0; i < sizeof(struct nvram_header); i += 4)
+ *dst++ = __raw_readl(src++);
+ for (; i < *nvram_len; i += 4)
+ *dst++ = readl(src++);
+
+ return 0;
+}
+
+int bcm47xx_nvram_getenv(const struct device *dev, const char *name, char *val,
+ size_t val_len)
+{
+ char *var, *value, *end, *eq;
+ struct bcm47xx_nvram *nvram;
+
+ if (!dev)
+ return -ENODEV;
+
+ nvram = dev_get_drvdata(dev);
+
+ if (!name || !nvram || !nvram->nvram_len)
+ return -EINVAL;
+
+ /* Look for name=value and return value */
+ var = nvram->nvram_buf + sizeof(struct nvram_header);
+ end = nvram->nvram_buf + nvram->nvram_len - 2;
+ end[0] = end[1] = '\0';
+ for (; *var; var = value + strlen(value) + 1) {
+ eq = strchr(var, '=');
+ if (!eq)
+ break;
+ value = eq + 1;
+ if ((eq - var) == strlen(name) &&
+ strncmp(var, name, (eq - var)) == 0) {
+ return snprintf(val, val_len, "%s", value);
+ }
+ }
+ return -ENOENT;
+}
+EXPORT_SYMBOL(bcm47xx_nvram_getenv);
+
+int bcm47xx_nvram_gpio_pin(const struct device *dev, const char *name)
+{
+ int i, err;
+ char nvram_var[10];
+ char buf[30];
+
+ if (!dev)
+ return -ENODEV;
+
+ for (i = 0; i < 32; i++) {
+ err = snprintf(nvram_var, sizeof(nvram_var), "gpio%i", i);
+ if (err <= 0)
+ continue;
+ err = bcm47xx_nvram_getenv(dev, nvram_var, buf, sizeof(buf));
+ if (err <= 0)
+ continue;
+ if (!strcmp(name, buf))
+ return i;
+ }
+ return -ENOENT;
+}
+EXPORT_SYMBOL(bcm47xx_nvram_gpio_pin);
+
+static int bcm47xx_nvram_probe(struct platform_device *pdev)
+{
+ struct device *dev = &pdev->dev;
+ struct device_node *np = dev->of_node;
+ struct bcm47xx_nvram *nvram;
+ int err;
+ struct resource flash_mem;
+ void __iomem *mmio;
+
+ /* Alloc */
+ nvram = devm_kzalloc(dev, sizeof(*nvram), GFP_KERNEL);
+ if (!nvram)
+ return -ENOMEM;
+
+ err = of_address_to_resource(np, 0, &flash_mem);
+ if (err)
+ return err;
+
+ mmio = ioremap_nocache(flash_mem.start, resource_size(&flash_mem));
+ if (!mmio)
+ return -ENOMEM;
+
+ err = nvram_find_and_copy(dev, mmio, resource_size(&flash_mem),
+ &nvram->nvram_buf, &nvram->nvram_len);
+ if (err)
+ goto err_unmap_mmio;
+
+ platform_set_drvdata(pdev, nvram);
+
+err_unmap_mmio:
+ iounmap(mmio);
+ return err;
+}
+
+static const struct of_device_id bcm47xx_nvram_of_match_table[] = {
+ { .compatible = "brcm,bcm47xx-nvram", },
+ {},
+};
+MODULE_DEVICE_TABLE(of, mvebu_pcie_of_match_table);
+
+static struct platform_driver bcm47xx_nvram_driver = {
+ .driver = {
+ .owner = THIS_MODULE,
+ .name = "bcm47xx-nvram",
+ .of_match_table = bcm47xx_nvram_of_match_table,
+ /* driver unloading/unbinding currently not supported */
+ .suppress_bind_attrs = true,
+ },
+ .probe = bcm47xx_nvram_probe,
+};
+module_platform_driver(bcm47xx_nvram_driver);
+
+MODULE_AUTHOR("Hauke Mehrtens <hauke@hauke-m.de>");
+MODULE_LICENSE("GPLv2");
@@ -411,7 +411,7 @@ static void b44_wap54g10_workaround(struct b44 *bp)
* see https://dev.openwrt.org/ticket/146
* check and reset bit "isolate"
*/
- if (bcm47xx_nvram_getenv("boardnum", buf, sizeof(buf)) < 0)
+ if (bcm47xx_nvram_getenv(NULL, "boardnum", buf, sizeof(buf)) < 0)
return;
if (simple_strtoul(buf, NULL, 0) == 2) {
err = __b44_readphy(bp, 0, MII_BMCR, &val);
@@ -952,7 +952,8 @@ static void bgmac_chip_reset(struct bgmac *bgmac)
BGMAC_CHIPCTL_1_IF_TYPE_MII;
char buf[4];
- if (bcm47xx_nvram_getenv("et_swtype", buf, sizeof(buf)) > 0) {
+ if (bcm47xx_nvram_getenv(NULL, "et_swtype", buf,
+ sizeof(buf)) > 0) {
if (kstrtou8(buf, 0, &et_swtype))
bgmac_err(bgmac, "Failed to parse et_swtype (%s)\n",
buf);
@@ -1501,7 +1502,7 @@ static int bgmac_probe(struct bcma_device *core)
}
bgmac->int_mask = BGMAC_IS_ERRMASK | BGMAC_IS_RX | BGMAC_IS_TX_MASK;
- if (bcm47xx_nvram_getenv("et0_no_txint", NULL, 0) == 0)
+ if (bcm47xx_nvram_getenv(NULL, "et0_no_txint", NULL, 0) == 0)
bgmac->int_mask &= ~BGMAC_IS_TX_MASK;
/* TODO: reset the external phy. Specs are needed */
@@ -319,7 +319,8 @@ static void ssb_pmu_pll_init(struct ssb_chipcommon *cc)
if (bus->bustype == SSB_BUSTYPE_SSB) {
char buf[20];
- if (bcm47xx_nvram_getenv("xtalfreq", buf, sizeof(buf)) >= 0)
+ if (bcm47xx_nvram_getenv(NULL, "xtalfreq", buf,
+ sizeof(buf)) >= 0)
crystalfreq = simple_strtoul(buf, NULL, 0);
}
@@ -15,9 +15,11 @@
#include <linux/types.h>
#include <linux/kernel.h>
+struct device;
+
struct nvram_header {
u32 magic;
- u32 len;
+ __le32 len;
u32 crc_ver_init; /* 0:7 crc, 8:15 ver, 16:31 sdram_init */
u32 config_refresh; /* 0:15 sdram_config, 16:31 sdram_refresh */
u32 config_ncdl; /* ncdl values for memc */
@@ -33,18 +35,21 @@ struct nvram_header {
#define NVRAM_MAX_VALUE_LEN 255
#define NVRAM_MAX_PARAM_LEN 64
-#ifdef CONFIG_BCM47XX
-int bcm47xx_nvram_getenv(const char *name, char *val, size_t val_len);
+#if defined(CONFIG_BCM47XX) || defined(CONFIG_BCM47XX_NVRAM)
+int bcm47xx_nvram_getenv(const struct device *dev, const char *name, char *val,
+ size_t val_len);
-int bcm47xx_nvram_gpio_pin(const char *name);
+int bcm47xx_nvram_gpio_pin(const struct device *dev, const char *name);
#else
-static inline int bcm47xx_nvram_getenv(const char *name, char *val,
+static inline int bcm47xx_nvram_getenv(const struct device *dev,
+ const char *name, char *val,
size_t val_len)
{
return -ENXIO;
}
-static inline int bcm47xx_nvram_gpio_pin(const char *name)
+static inline int bcm47xx_nvram_gpio_pin(const struct device *dev,
+ const char *name)
{
return -ENXIO;
}
This adds a new driver which searches at a given memory range for a nvram like it is used on the bcm47xx and bcm53xx SoCs with ARM and MIPS CPUs. This driver provides acces to this nvram to other device in the device tree. You have to specify the memory ranges where the content of the flash chip is memory mapped and this driver will search there for some nvram and parse it. Other drivers can use this driver to access the device nvram. The nvram is used to store board configurations like the mac addresses, the switch configuration and the calibration data for the wifi devices. This was copied from arch/mips/bcm47xx/nvram.c and modified to interact with device tree. My plan is to make the MIPS bcm47xx also use this new driver some time later. Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de> --- .../devicetree/bindings/misc/bcm47xx-nvram.txt | 19 ++ arch/mips/bcm47xx/board.c | 40 ++-- arch/mips/bcm47xx/nvram.c | 7 +- arch/mips/bcm47xx/setup.c | 4 +- arch/mips/bcm47xx/sprom.c | 4 +- arch/mips/bcm47xx/time.c | 2 +- drivers/misc/Kconfig | 13 ++ drivers/misc/Makefile | 1 + drivers/misc/bcm47xx-nvram.c | 215 +++++++++++++++++++++ drivers/net/ethernet/broadcom/b44.c | 2 +- drivers/net/ethernet/broadcom/bgmac.c | 5 +- drivers/ssb/driver_chipcommon_pmu.c | 3 +- include/linux/bcm47xx_nvram.h | 17 +- 13 files changed, 294 insertions(+), 38 deletions(-) create mode 100644 Documentation/devicetree/bindings/misc/bcm47xx-nvram.txt create mode 100644 drivers/misc/bcm47xx-nvram.c