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eeprom: at24: check if the chip is functional in probe()

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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 <bgolaszewski@baylibre.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
This commit is contained in:
Bartosz Golaszewski 2016-08-12 13:32:57 +02:00 committed by Wolfram Sang
parent 56025e7bc2
commit 00f0ea70d2
1 changed files with 13 additions and 2 deletions
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15
drivers/misc/eeprom/at24.c
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@ -593,6 +593,7 @@ static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id)
struct at24_data *at24; struct at24_data *at24;
int err; int err;
unsigned i, num_addresses; unsigned i, num_addresses;
u8 test_byte;
if (client->dev.platform_data) { if (client->dev.platform_data) {
chip = *(struct at24_platform_data *)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.name = dev_name(&client->dev);
at24->nvmem_config.dev = &client->dev; at24->nvmem_config.dev = &client->dev;
at24->nvmem_config.read_only = !writable; 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; goto err_clients;
} }
i2c_set_clientdata(client, at24);
dev_info(&client->dev, "%u byte %s EEPROM, %s, %u bytes/write\n", dev_info(&client->dev, "%u byte %s EEPROM, %s, %u bytes/write\n",
chip.byte_len, client->name, chip.byte_len, client->name,
writable ? "writable" : "read-only", at24->write_max); writable ? "writable" : "read-only", at24->write_max);