[RESEND PATCH v2 04/13] eeprom: at24: make locking more fine-grained

[Bartosz Golaszewski]

The only field in struct at24_data that needs locking in the module
code is u8 *writebuf. Other data is already protected by i2c core.

Rename the lock in at24_data to wrbuf_lock and only use it where
writebuf is accessed.

Signed-off-by: Bartosz Golaszewski <bgolaszew...@baylibre.com>
---
 drivers/misc/eeprom/at24.c | 28 +++++-----------------------
 1 file changed, 5 insertions(+), 23 deletions(-)

diff --git a/drivers/misc/eeprom/at24.c b/drivers/misc/eeprom/at24.c
index 744c526..9e01428 100644
--- a/drivers/misc/eeprom/at24.c
+++ b/drivers/misc/eeprom/at24.c
@@ -59,13 +59,8 @@ struct at24_data {
        int use_smbus;
        int use_smbus_write;
 
-       /*
-        * Lock protects against activities from other Linux tasks,
-        * but not from changes by other I2C masters.
-        */
-       struct mutex lock;
-
        u8 *writebuf;
+       struct mutex wrbuf_lock;
        unsigned write_max;
        unsigned num_addresses;
 
@@ -260,12 +255,6 @@ static ssize_t at24_read(struct at24_data *at24,
        if (unlikely(!count))
                return count;
 
-       /*
-        * Read data from chip, protecting against concurrent updates
-        * from this host, but not from other I2C masters.
-        */
-       mutex_lock(&at24->lock);
-
        while (count) {
                ssize_t status;
 
@@ -281,8 +270,6 @@ static ssize_t at24_read(struct at24_data *at24,
                retval += status;
        }
 
-       mutex_unlock(&at24->lock);
-
        return retval;
 }
 
@@ -322,6 +309,8 @@ static ssize_t at24_eeprom_write(struct at24_data *at24, 
const char *buf,
                msg.addr = client->addr;
                msg.flags = 0;
 
+               mutex_lock(&at24->wrbuf_lock);
+
                /* msg.buf is u8 and casts will mask the values */
                msg.buf = at24->writebuf;
                if (at24->chip.flags & AT24_FLAG_ADDR16)
@@ -356,6 +345,7 @@ static ssize_t at24_eeprom_write(struct at24_data *at24, 
const char *buf,
                                status = count;
                } else {
                        status = i2c_transfer(client->adapter, &msg, 1);
+                       mutex_unlock(&at24->wrbuf_lock);
                        if (status == 1)
                                status = count;
                }
@@ -380,12 +370,6 @@ static ssize_t at24_write(struct at24_data *at24, const 
char *buf, loff_t off,
        if (unlikely(!count))
                return count;
 
-       /*
-        * Write data to chip, protecting against concurrent updates
-        * from this host, but not from other I2C masters.
-        */
-       mutex_lock(&at24->lock);
-
        while (count) {
                ssize_t status;
 
@@ -401,8 +385,6 @@ static ssize_t at24_write(struct at24_data *at24, const 
char *buf, loff_t off,
                retval += status;
        }
 
-       mutex_unlock(&at24->lock);
-
        return retval;
 }
 
@@ -566,7 +548,7 @@ static int at24_probe(struct i2c_client *client, const 
struct i2c_device_id *id)
        if (!at24)
                return -ENOMEM;
 
-       mutex_init(&at24->lock);
+       mutex_init(&at24->wrbuf_lock);
        at24->use_smbus = use_smbus;
        at24->use_smbus_write = use_smbus_write;
        at24->chip = chip;
-- 
2.7.4