From 00f0ea70d2b82b7d7afeb1bdedc9169eb8ea6675 Mon Sep 17 00:00:00 2001 From: Bartosz Golaszewski Date: Fri, 12 Aug 2016 13:32:57 +0200 Subject: [PATCH] eeprom: at24: check if the chip is functional in probe() The at24 driver doesn't check if the chip is functional in its probe function. This leads to instantiating devices that are not physically present. For example the cape EEPROMs for BeagleBone Black are defined in the device tree at four addresses on i2c2, but normally only one of them is present. If the userspace doesn't know the location in advance, it will need to check if reading the nvmem attributes fails to determine which EEPROM is actually there. Try to read a single byte in probe() and bail-out with -ENODEV if the read fails. Signed-off-by: Bartosz Golaszewski Signed-off-by: Wolfram Sang --- drivers/misc/eeprom/at24.c | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-) diff --git a/drivers/misc/eeprom/at24.c b/drivers/misc/eeprom/at24.c index 3cdf8e1ca0ad..051b14766ef9 100644 --- a/drivers/misc/eeprom/at24.c +++ b/drivers/misc/eeprom/at24.c @@ -593,6 +593,7 @@ static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id) struct at24_data *at24; int err; unsigned i, num_addresses; + u8 test_byte; if (client->dev.platform_data) { chip = *(struct at24_platform_data *)client->dev.platform_data; @@ -743,6 +744,18 @@ static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id) } } + i2c_set_clientdata(client, at24); + + /* + * Perform a one-byte test read to verify that the + * chip is functional. + */ + err = at24_read(at24, 0, &test_byte, 1); + if (err) { + err = -ENODEV; + goto err_clients; + } + at24->nvmem_config.name = dev_name(&client->dev); at24->nvmem_config.dev = &client->dev; at24->nvmem_config.read_only = !writable; @@ -764,8 +777,6 @@ static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id) goto err_clients; } - i2c_set_clientdata(client, at24); - dev_info(&client->dev, "%u byte %s EEPROM, %s, %u bytes/write\n", chip.byte_len, client->name, writable ? "writable" : "read-only", at24->write_max); -- 2.39.5