memory_accessor: implement the new memory_accessor interfaces for SPI EEPROMs

- Define new setup() hook to export the accessor
 - Implement accessor methods

Moves some error checking out of the sysfs interface code into the layer
below it, which is now shared by both sysfs and memory access code.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>
Cc: Jean Delvare <khali@linux-fr.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 50 insertions, 14 deletions

diff --git a/drivers/misc/eeprom/at25.c b/drivers/misc/eeprom/at25.c
index 290dbe99647a..6bc0dac5c1e8 100644
--- a/drivers/misc/eeprom/at25.c
+++ b/drivers/misc/eeprom/at25.c
@@ -30,6 +30,7 @@
 
 struct at25_data {
         struct spi_device       *spi;
+        struct memory_accessor  mem;
         struct mutex            lock;
         struct spi_eeprom       chip;
         struct bin_attribute    bin;
@@ -75,6 +76,13 @@ at25_ee_read(
         struct spi_transfer     t[2];
         struct spi_message      m;
 
+        if (unlikely(offset >= at25->bin.size))
+                return 0;
+        if ((offset + count) > at25->bin.size)
+                count = at25->bin.size - offset;
+        if (unlikely(!count))
+                return count;
+
         cp = command;
         *cp++ = AT25_READ;
 
@@ -127,13 +135,6 @@ at25_bin_read(struct kobject *kobj, struct bin_attribute *bin_attr,
         dev = container_of(kobj, struct device, kobj);
         at25 = dev_get_drvdata(dev);
 
-        if (unlikely(off >= at25->bin.size))
-                return 0;
-        if ((off + count) > at25->bin.size)
-                count = at25->bin.size - off;
-        if (unlikely(!count))
-                return count;
-
         return at25_ee_read(at25, buf, off, count);
 }
 
@@ -146,6 +147,13 @@ at25_ee_write(struct at25_data *at25, char *buf, loff_t off, size_t count)
         unsigned                buf_size;
         u8                      *bounce;
 
+        if (unlikely(off >= at25->bin.size))
+                return -EFBIG;
+        if ((off + count) > at25->bin.size)
+                count = at25->bin.size - off;
+        if (unlikely(!count))
+                return count;
+
         /* Temp buffer starts with command and address */
         buf_size = at25->chip.page_size;
         if (buf_size > io_limit)
@@ -253,18 +261,31 @@ at25_bin_write(struct kobject *kobj, struct bin_attribute *bin_attr,
         dev = container_of(kobj, struct device, kobj);
         at25 = dev_get_drvdata(dev);
 
-        if (unlikely(off >= at25->bin.size))
-                return -EFBIG;
-        if ((off + count) > at25->bin.size)
-                count = at25->bin.size - off;
-        if (unlikely(!count))
-                return count;
-
         return at25_ee_write(at25, buf, off, count);
 }
 
 /*-------------------------------------------------------------------------*/
 
+/* Let in-kernel code access the eeprom data. */
+
+static ssize_t at25_mem_read(struct memory_accessor *mem, char *buf,
+                         off_t offset, size_t count)
+{
+        struct at25_data *at25 = container_of(mem, struct at25_data, mem);
+
+        return at25_ee_read(at25, buf, offset, count);
+}
+
+static ssize_t at25_mem_write(struct memory_accessor *mem, char *buf,
+                          off_t offset, size_t count)
+{
+        struct at25_data *at25 = container_of(mem, struct at25_data, mem);
+
+        return at25_ee_write(at25, buf, offset, count);
+}
+
+/*-------------------------------------------------------------------------*/
+
 static int at25_probe(struct spi_device *spi)
 {
         struct at25_data        *at25 = NULL;
@@ -317,6 +338,10 @@ static int at25_probe(struct spi_device *spi)
         at25->addrlen = addrlen;
 
         /* Export the EEPROM bytes through sysfs, since that's convenient.
+         * And maybe to other kernel code; it might hold a board's Ethernet
+         * address, or board-specific calibration data generated on the
+         * manufacturing floor.
+         *
          * Default to root-only access to the data; EEPROMs often hold data
          * that's sensitive for read and/or write, like ethernet addresses,
          * security codes, board-specific manufacturing calibrations, etc.
@@ -324,17 +349,22 @@ static int at25_probe(struct spi_device *spi)
         at25->bin.attr.name = "eeprom";
         at25->bin.attr.mode = S_IRUSR;
         at25->bin.read = at25_bin_read;
+        at25->mem.read = at25_mem_read;
 
         at25->bin.size = at25->chip.byte_len;
         if (!(chip->flags & EE_READONLY)) {
                 at25->bin.write = at25_bin_write;
                 at25->bin.attr.mode |= S_IWUSR;
+                at25->mem.write = at25_mem_write;
         }
 
         err = sysfs_create_bin_file(&spi->dev.kobj, &at25->bin);
         if (err)
                 goto fail;
 
+        if (chip->setup)
+                chip->setup(&at25->mem, chip->context);
+
         dev_info(&spi->dev, "%Zd %s %s eeprom%s, pagesize %u\n",
                 (at25->bin.size < 1024)
                         ? at25->bin.size
diff --git a/include/linux/spi/eeprom.h b/include/linux/spi/eeprom.h
index 1085212c446e..306e7b1c69ed 100644
--- a/include/linux/spi/eeprom.h
+++ b/include/linux/spi/eeprom.h
@@ -1,6 +1,8 @@
 #ifndef __LINUX_SPI_EEPROM_H
 #define __LINUX_SPI_EEPROM_H
 
+#include <linux/memory.h>
+
 /*
  * Put one of these structures in platform_data for SPI EEPROMS handled
  * by the "at25" driver.  On SPI, most EEPROMS understand the same core
@@ -17,6 +19,10 @@ struct spi_eeprom {
 #define EE_ADDR2        0x0002                  /* 16 bit addrs */
 #define EE_ADDR3        0x0004                  /* 24 bit addrs */
 #define EE_READONLY     0x0008                  /* disallow writes */
+
+        /* for exporting this chip's data to other kernel code */
+        void (*setup)(struct memory_accessor *mem, void *context);
+        void *context;
 };
 
 #endif /* __LINUX_SPI_EEPROM_H */