On Wed, Aug 10, 2016 at 03:54:17PM +0200, Bartosz Golaszewski wrote: > 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.
That's basically OK... > > Signed-off-by: Bartosz Golaszewski <[email protected]> > --- > drivers/misc/eeprom/at24.c | 10 ++++++++++ > 1 file changed, 10 insertions(+) > > diff --git a/drivers/misc/eeprom/at24.c b/drivers/misc/eeprom/at24.c > index 3cdf8e1..ed1e4eb 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; > + char c; u8? > > if (client->dev.platform_data) { > chip = *(struct at24_platform_data *)client->dev.platform_data; > @@ -780,6 +781,15 @@ static int at24_probe(struct i2c_client *client, const > struct i2c_device_id *id) > if (chip.setup) > chip.setup(at24->nvmem, chip.context); > > + err = at24_read(at24, 0, &c, 1); Can't we do this before registering dummy clients and nvmem registration? > + if (err) { > + dev_err(&client->dev, > + "error reading the test byte from EEPROM: %d\n", err); I don't think we should print an error in case of ENODEV. > + nvmem_unregister(at24->nvmem); > + err = -ENODEV; > + goto err_clients; > + } > + > return 0; > > err_clients: > -- > 2.7.4 >
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