Re: [PATCH] Input: elan_i2c - check if device is there before really probing

[Guenter Roeck]

On 05/03/2017 11:29 PM, Dmitry Torokhov wrote:

Before trying to properly initialize the touchpad and generate bunch of
errors, let's first see it there is anything at the given address. If we
get error, fail silently with -ENXIO.

Signed-off-by: Dmitry Torokhov <dmitry.torok...@gmail.com>
---
 drivers/input/mouse/elan_i2c_core.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/input/mouse/elan_i2c_core.c 
b/drivers/input/mouse/elan_i2c_core.c
index 5d3b53dd2fa2..0479730e7c5c 100644
--- a/drivers/input/mouse/elan_i2c_core.c
+++ b/drivers/input/mouse/elan_i2c_core.c
@@ -1040,6 +1040,7 @@ static int elan_probe(struct i2c_client *client,
        const struct elan_transport_ops *transport_ops;
        struct device *dev = &client->dev;
        struct elan_tp_data *data;
+       union i2c_smbus_data dummy;
        unsigned long irqflags;
        int error;

@@ -1091,6 +1092,14 @@ static int elan_probe(struct i2c_client *client,
                return error;
        }

+       /* Make sure there is something at this address */
+       error = i2c_smbus_xfer(client->adapter, client->addr, 0,
+                              I2C_SMBUS_READ, 0, I2C_SMBUS_BYTE, &dummy);

Can't you just call i2c_smbus_read_byte_data(client, 0); and check if it returns
an error ?

Thanks,
Guenter

+       if (error) {
+               dev_dbg(&client->dev, "nothing at this address: %d\n", error);
+               return -ENXIO;
+       }
+
        /* Initialize the touchpad. */
        error = elan_initialize(data);
        if (error)