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SubjectRe: [PATCH] eeprom: at24: check if the chip is functional in probe()
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 <bgolaszewski@baylibre.com>
> ---
> 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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