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Subject[RFC 06/24] char/nvram: Adopt arch_nvram_ops
Different platforms and architectures offer different NVRAM sizes and
access methods. E.g. PPC32 has byte-at-a-time read/write functions whereas
PPC64 has byte-range read/write functions. Adopt the nvram_ops struct so
the nvram module can call such functions as are defined by the various
platforms and architectures.

Signed-off-by: Finn Thain <fthain@telegraphics.com.au>

---

The #ifdefs here restrict the procfs and checksumming code to those
architectures with PC-style RTC NVRAM. There may be a better place for
that code but it's an open question. See https://lkml.org/lkml/2015/2/3/22

The procfs code here, if irrelevant to ARM platforms, could be moved to
arch/x86 (like the earlier patch does for m68k code) and the nvram ops
could implemented and exported by the rtc-cmos driver instead. This
would eliminate these #ifdefs.

---
drivers/char/nvram.c | 30 +++++++++++++++++++++++++++---
include/linux/nvram.h | 2 ++
2 files changed, 29 insertions(+), 3 deletions(-)

Index: linux/drivers/char/nvram.c
===================================================================
--- linux.orig/drivers/char/nvram.c 2015-05-31 11:01:05.000000000 +1000
+++ linux/drivers/char/nvram.c 2015-05-31 11:01:06.000000000 +1000
@@ -51,9 +51,12 @@ static DEFINE_MUTEX(nvram_mutex);
static DEFINE_SPINLOCK(nvram_state_lock);
static int nvram_open_cnt; /* #times opened */
static int nvram_open_mode; /* special open modes */
+static ssize_t nvram_size;
#define NVRAM_WRITE 1 /* opened for writing (exclusive) */
#define NVRAM_EXCL 2 /* opened with O_EXCL */

+#if defined(CONFIG_X86) || defined(CONFIG_ARM)
+
/*
* These functions are provided to be called internally or by other parts of
* the kernel. It's up to the caller to ensure correct checksum before reading
@@ -161,6 +164,20 @@ void nvram_set_checksum(void)
}
#endif /* 0 */

+static ssize_t nvram_get_size(void)
+{
+ return NVRAM_BYTES;
+}
+
+const struct nvram_ops arch_nvram_ops = {
+ .read_byte = nvram_read_byte,
+ .write_byte = nvram_write_byte,
+ .get_size = nvram_get_size,
+};
+EXPORT_SYMBOL(arch_nvram_ops);
+
+#endif /* CONFIG_X86 || CONFIG_ARM */
+
/*
* The are the file operation function for user access to /dev/nvram
*/
@@ -332,7 +349,7 @@ static int nvram_misc_release(struct ino
return 0;
}

-#ifdef CONFIG_PROC_FS
+#if defined(CONFIG_PROC_FS) && (defined(CONFIG_X86) || defined(CONFIG_ARM))

static char *floppy_types[] = {
"none", "5.25'' 360k", "5.25'' 1.2M", "3.5'' 720k", "3.5'' 1.44M",
@@ -459,13 +476,20 @@ static int __init nvram_module_init(void
{
int ret;

+ if (arch_nvram_ops.get_size == NULL)
+ return -ENODEV;
+
+ nvram_size = arch_nvram_ops.get_size();
+ if (nvram_size < 0)
+ return nvram_size;
+
ret = misc_register(&nvram_misc);
if (ret) {
pr_err("nvram: can't misc_register on minor=%d\n", NVRAM_MINOR);
return ret;
}

-#ifdef CONFIG_PROC_FS
+#if defined(CONFIG_PROC_FS) && (defined(CONFIG_X86) || defined(CONFIG_ARM))
if (!proc_create("driver/nvram", 0, NULL, &nvram_proc_fops)) {
pr_err("nvram: can't create /proc/driver/nvram\n");
misc_deregister(&nvram_misc);
@@ -479,7 +503,7 @@ static int __init nvram_module_init(void

static void __exit nvram_module_exit(void)
{
-#ifdef CONFIG_PROC_FS
+#if defined(CONFIG_PROC_FS) && (defined(CONFIG_X86) || defined(CONFIG_ARM))
remove_proc_entry("driver/nvram", NULL);
#endif
misc_deregister(&nvram_misc);
Index: linux/include/linux/nvram.h
===================================================================
--- linux.orig/include/linux/nvram.h 2015-05-31 11:01:03.000000000 +1000
+++ linux/include/linux/nvram.h 2015-05-31 11:01:06.000000000 +1000
@@ -14,6 +14,8 @@ extern int nvram_check_checksum(void);
struct nvram_ops {
ssize_t (*read)(char *, size_t, loff_t *);
ssize_t (*write)(char *, size_t, loff_t *);
+ unsigned char (*read_byte)(int);
+ void (*write_byte)(unsigned char, int);
ssize_t (*get_size)(void);
};




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