[PATCH] eeprom: add non-cached sysfs read access to EEPROM data

[Petri Gynther]

Add "eeprom-nc" sysfs attribute to provide non-cached read access
to EEPROM data. This is needed because some EEPROM-like devices
contain constantly changing real-time diagnostic data that cannot
be cached in kernel memory.

Signed-off-by: Petri Gynther <pgynt...@google.com>
---
 drivers/misc/eeprom/eeprom.c |   30 +++++++++++++++++++++++++++---
 1 files changed, 27 insertions(+), 3 deletions(-)

diff --git a/drivers/misc/eeprom/eeprom.c b/drivers/misc/eeprom/eeprom.c
index 2c27193..101260b 100644
--- a/drivers/misc/eeprom/eeprom.c
+++ b/drivers/misc/eeprom/eeprom.c
@@ -39,6 +39,10 @@ I2C_CLIENT_INSMOD_1(eeprom);
 /* Size of EEPROM in bytes */
 #define EEPROM_SIZE            256
 
+/* EEPROM read modes */
+#define EEPROM_READ_CACHED      0
+#define EEPROM_READ_NONCACHED   1
+
 /* possible types of eeprom devices */
 enum eeprom_nature {
        UNKNOWN,
@@ -55,14 +59,16 @@ struct eeprom_data {
 };
 
 
-static void eeprom_update_client(struct i2c_client *client, u8 slice)
+static void eeprom_update_client(struct i2c_client *client, u8 slice,
+                                int eeprom_read_mode)
 {
        struct eeprom_data *data = i2c_get_clientdata(client);
        int i;
 
        mutex_lock(&data->update_lock);
 
-       if (!(data->valid & (1 << slice)) ||
+       if (eeprom_read_mode == EEPROM_READ_NONCACHED ||
+           !(data->valid & (1 << slice)) ||
            time_after(jiffies, data->last_updated[slice] + 300 * HZ)) {
                dev_dbg(&client->dev, "Starting eeprom update, slice %u\n", 
slice);
 
@@ -102,7 +108,7 @@ static ssize_t eeprom_read(struct kobject *kobj, struct 
bin_attribute *bin_attr,
 
        /* Only refresh slices which contain requested bytes */
        for (slice = off >> 5; slice <= (off + count - 1) >> 5; slice++)
-               eeprom_update_client(client, slice);
+               eeprom_update_client(client, slice, (int)bin_attr->private);
 
        /* Hide Vaio private settings to regular users:
           - BIOS passwords: bytes 0x00 to 0x0f
@@ -132,6 +138,17 @@ static struct bin_attribute eeprom_attr = {
        },
        .size = EEPROM_SIZE,
        .read = eeprom_read,
+       .private = (void *)EEPROM_READ_CACHED,
+};
+
+static struct bin_attribute eeprom_nc_attr = {
+       .attr = {
+               .name = "eeprom-nc",
+               .mode = S_IRUGO,
+       },
+       .size = EEPROM_SIZE,
+       .read = eeprom_read,
+       .private = (void *)EEPROM_READ_NONCACHED,
 };
 
 /* Return 0 if detection is successful, -ENODEV otherwise */
@@ -202,8 +219,14 @@ static int eeprom_probe(struct i2c_client *client,
        if (err)
                goto exit_kfree;
 
+       err = sysfs_create_bin_file(&client->dev.kobj, &eeprom_nc_attr);
+       if (err)
+               goto exit_sysfs_clean;
+
        return 0;
 
+exit_sysfs_clean:
+       sysfs_remove_bin_file(&client->dev.kobj, &eeprom_attr);
 exit_kfree:
        kfree(data);
 exit:
@@ -212,6 +235,7 @@ exit:
 
 static int eeprom_remove(struct i2c_client *client)
 {
+       sysfs_remove_bin_file(&client->dev.kobj, &eeprom_nc_attr);
        sysfs_remove_bin_file(&client->dev.kobj, &eeprom_attr);
        kfree(i2c_get_clientdata(client));
 
-- 
1.5.4.3

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