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Subject[RFC 04/24] m68k/atari: Replace nvram_{read,write}_byte with arch_nvram_ops
By implementing an arch_nvram_ops struct, any platform can re-use the
drivers/char/nvram module without needing any arch-specific code
in that module. Atari does so here.

Atari has one user of nvram_check_checksum() whereas the other platforms
(i.e. x86 and ARM platforms) have none at all. Replace this
validate-checksum-and-read-byte sequence with the equivalent
rtc_nvram_ops.read() call and remove the now unused functions.

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

---

The advantage of the new ops struct over the old global nvram_* functions
is that the misc device module can be shared by different platforms
without requiring every platform to implement every nvram_* function.
E.g. only RTC "CMOS" NVRAMs have a checksum and only PowerPC platforms
have a "sync" ioctl.

---
arch/m68k/atari/nvram.c | 89 ++++++++++++++++++++++++++++------------------
drivers/scsi/atari_scsi.c | 8 ++--
include/linux/nvram.h | 9 ++++
3 files changed, 70 insertions(+), 36 deletions(-)

Index: linux/arch/m68k/atari/nvram.c
===================================================================
--- linux.orig/arch/m68k/atari/nvram.c 2015-05-31 11:01:01.000000000 +1000
+++ linux/arch/m68k/atari/nvram.c 2015-05-31 11:01:03.000000000 +1000
@@ -38,33 +38,12 @@ unsigned char __nvram_read_byte(int i)
return CMOS_READ(NVRAM_FIRST_BYTE + i);
}

-unsigned char nvram_read_byte(int i)
-{
- unsigned long flags;
- unsigned char c;
-
- spin_lock_irqsave(&rtc_lock, flags);
- c = __nvram_read_byte(i);
- spin_unlock_irqrestore(&rtc_lock, flags);
- return c;
-}
-EXPORT_SYMBOL(nvram_read_byte);
-
/* This races nicely with trying to read with checksum checking */
void __nvram_write_byte(unsigned char c, int i)
{
CMOS_WRITE(c, NVRAM_FIRST_BYTE + i);
}

-void nvram_write_byte(unsigned char c, int i)
-{
- unsigned long flags;
-
- spin_lock_irqsave(&rtc_lock, flags);
- __nvram_write_byte(c, i);
- spin_unlock_irqrestore(&rtc_lock, flags);
-}
-
/* On Ataris, the checksum is over all bytes except the checksum bytes
* themselves; these are at the very end.
*/
@@ -83,18 +62,6 @@ int __nvram_check_checksum(void)
(__nvram_read_byte(ATARI_CKS_LOC + 1) == (sum & 0xff));
}

-int nvram_check_checksum(void)
-{
- unsigned long flags;
- int rv;
-
- spin_lock_irqsave(&rtc_lock, flags);
- rv = __nvram_check_checksum();
- spin_unlock_irqrestore(&rtc_lock, flags);
- return rv;
-}
-EXPORT_SYMBOL(nvram_check_checksum);
-
static void __nvram_set_checksum(void)
{
int i;
@@ -106,6 +73,62 @@ static void __nvram_set_checksum(void)
__nvram_write_byte(sum, ATARI_CKS_LOC + 1);
}

+static ssize_t nvram_read(char *buf, size_t count, loff_t *ppos)
+{
+ char *p = buf;
+ loff_t i;
+
+ spin_lock_irq(&rtc_lock);
+
+ if (!__nvram_check_checksum()) {
+ spin_unlock_irq(&rtc_lock);
+ return -EIO;
+ }
+
+ for (i = *ppos; count > 0 && i < NVRAM_BYTES; --count, ++i, ++p)
+ *p = __nvram_read_byte(i);
+
+ spin_unlock_irq(&rtc_lock);
+
+ *ppos = i;
+ return p - buf;
+}
+
+static ssize_t nvram_write(char *buf, size_t count, loff_t *ppos)
+{
+ char *p = buf;
+ loff_t i;
+
+ spin_lock_irq(&rtc_lock);
+
+ if (!__nvram_check_checksum()) {
+ spin_unlock_irq(&rtc_lock);
+ return -EIO;
+ }
+
+ for (i = *ppos; count > 0 && i < NVRAM_BYTES; --count, ++i, ++p)
+ __nvram_write_byte(*p, i);
+
+ __nvram_set_checksum();
+
+ spin_unlock_irq(&rtc_lock);
+
+ *ppos = i;
+ return p - buf;
+}
+
+static ssize_t nvram_get_size(void)
+{
+ return NVRAM_BYTES;
+}
+
+const struct nvram_ops arch_nvram_ops = {
+ .read = nvram_read,
+ .write = nvram_write,
+ .get_size = nvram_get_size,
+};
+EXPORT_SYMBOL(arch_nvram_ops);
+
#ifdef CONFIG_PROC_FS
static struct {
unsigned char val;
Index: linux/drivers/scsi/atari_scsi.c
===================================================================
--- linux.orig/drivers/scsi/atari_scsi.c 2015-05-31 11:01:00.000000000 +1000
+++ linux/drivers/scsi/atari_scsi.c 2015-05-31 11:01:03.000000000 +1000
@@ -880,13 +880,15 @@ static int __init atari_scsi_probe(struc
#ifdef CONFIG_NVRAM
else
/* Test if a host id is set in the NVRam */
- if (ATARIHW_PRESENT(TT_CLK) && nvram_check_checksum()) {
- unsigned char b = nvram_read_byte(14);
+ if (ATARIHW_PRESENT(TT_CLK)) {
+ unsigned char b;
+ loff_t offset = 14;
+ ssize_t count = arch_nvram_ops.read(&b, 1, &offset);

/* Arbitration enabled? (for TOS)
* If yes, use configured host ID
*/
- if (b & 0x80)
+ if ((count == 1) && (b & 0x80))
atari_scsi_template.this_id = b & 7;
}
#endif
Index: linux/include/linux/nvram.h
===================================================================
--- linux.orig/include/linux/nvram.h 2015-05-31 11:00:59.000000000 +1000
+++ linux/include/linux/nvram.h 2015-05-31 11:01:03.000000000 +1000
@@ -10,4 +10,13 @@ extern void __nvram_write_byte(unsigned
extern void nvram_write_byte(unsigned char c, int i);
extern int __nvram_check_checksum(void);
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 *);
+ ssize_t (*get_size)(void);
+};
+
+extern const struct nvram_ops arch_nvram_ops;
+
#endif /* _LINUX_NVRAM_H */



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