i2c: slave: add error messages to slave core

Inform users what went wrong from the core, so drivers don't have to do
it.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Acked-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

1 files changed, 17 insertions, 5 deletions

diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
index 987c124432c5..2a627eb0365b 100644
--- a/drivers/i2c/i2c-core.c
+++ b/drivers/i2c/i2c-core.c
@@ -2914,18 +2914,24 @@ int i2c_slave_register(struct i2c_client *client, i2c_slave_cb_t slave_cb)
 {
         int ret;
 
-        if (!client || !slave_cb)
+        if (!client || !slave_cb) {
+                WARN(1, "insufficent data\n");
                 return -EINVAL;
+        }
 
         if (!(client->flags & I2C_CLIENT_TEN)) {
                 /* Enforce stricter address checking */
                 ret = i2c_check_addr_validity(client->addr);
-                if (ret)
+                if (ret) {
+                        dev_err(&client->dev, "%s: invalid address\n", __func__);
                         return ret;
+                }
         }
 
-        if (!client->adapter->algo->reg_slave)
+        if (!client->adapter->algo->reg_slave) {
+                dev_err(&client->dev, "%s: not supported by adapter\n", __func__);
                 return -EOPNOTSUPP;
+        }
 
         client->slave_cb = slave_cb;
 
@@ -2933,8 +2939,10 @@ int i2c_slave_register(struct i2c_client *client, i2c_slave_cb_t slave_cb)
         ret = client->adapter->algo->reg_slave(client);
         i2c_unlock_adapter(client->adapter);
 
-        if (ret)
+        if (ret) {
                 client->slave_cb = NULL;
+                dev_err(&client->dev, "%s: adapter returned error %d\n", __func__, ret);
+        }
 
         return ret;
 }
@@ -2944,8 +2952,10 @@ int i2c_slave_unregister(struct i2c_client *client)
 {
         int ret;
 
-        if (!client->adapter->algo->unreg_slave)
+        if (!client->adapter->algo->unreg_slave) {
+                dev_err(&client->dev, "%s: not supported by adapter\n", __func__);
                 return -EOPNOTSUPP;
+        }
 
         i2c_lock_adapter(client->adapter);
         ret = client->adapter->algo->unreg_slave(client);
@@ -2953,6 +2963,8 @@ int i2c_slave_unregister(struct i2c_client *client)
 
         if (ret == 0)
                 client->slave_cb = NULL;
+        else
+                dev_err(&client->dev, "%s: adapter returned error %d\n", __func__, ret);
 
         return ret;
 }