linux-kernel - Re: [PATCH v3 3/3] misc: eeprom: at24: register nvmem only after eeprom is ready to use

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Date:   Mon, 31 Aug 2020 19:21:39 +0200
From:   Bartosz Golaszewski <bgolaszewski@...libre.com>
To:     Vadym Kochan <vadym.kochan@...ision.eu>
Cc:     Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        Maxime Ripard <maxime.ripard@...e-electrons.com>,
        linux-i2c <linux-i2c@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 3/3] misc: eeprom: at24: register nvmem only after
 eeprom is ready to use

On Mon, Aug 31, 2020 at 3:56 AM Vadym Kochan <vadym.kochan@...ision.eu> wrote:
>
> During nvmem_register() the nvmem core sends notifications when:
>
>     - cell added
>     - nvmem added
>
> and during these notifications some callback func may access the nvmem
> device, which will fail in case of at24 eeprom because regulator and pm
> are enabled after nvmem_register().
>
> Signed-off-by: Vadym Kochan <vadym.kochan@...ision.eu>
> ---
> v3:
>     1) at24 driver enables regulator and pm state machine after nvmem
>        registration which does not allow to use it on handing NVMEM_PRE_ADD event.
>
>  drivers/misc/eeprom/at24.c | 11 +++++++----
>  1 file changed, 7 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/misc/eeprom/at24.c b/drivers/misc/eeprom/at24.c
> index 2591c21b2b5d..26a23abc053d 100644
> --- a/drivers/misc/eeprom/at24.c
> +++ b/drivers/misc/eeprom/at24.c
> @@ -692,10 +692,6 @@ static int at24_probe(struct i2c_client *client)
>         nvmem_config.word_size = 1;
>         nvmem_config.size = byte_len;
>
> -       at24->nvmem = devm_nvmem_register(dev, &nvmem_config);
> -       if (IS_ERR(at24->nvmem))
> -               return PTR_ERR(at24->nvmem);
> -
>         i2c_set_clientdata(client, at24);
>
>         err = regulator_enable(at24->vcc_reg);
> @@ -708,6 +704,13 @@ static int at24_probe(struct i2c_client *client)
>         pm_runtime_set_active(dev);
>         pm_runtime_enable(dev);
>
> +       at24->nvmem = devm_nvmem_register(dev, &nvmem_config);
> +       if (IS_ERR(at24->nvmem)) {
> +               pm_runtime_disable(dev);
> +               regulator_disable(at24->vcc_reg);
> +               return PTR_ERR(at24->nvmem);
> +       }
> +
>         /*
>          * Perform a one-byte test read to verify that the
>          * chip is functional.
> --
> 2.17.1
>

Good catch! Thanks for the patch. Can I queue it for fixes
independently from the earlier patches in this series?

Bart