linux-kernel - Re: [PATCH] eeprom: at24: don't use the default regmap locking

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Date:   Sun, 10 Dec 2017 19:57:06 +0100
From:   Bartosz Golaszewski <brgl@...ev.pl>
To:     Heiner Kallweit <hkallweit1@...il.com>
Cc:     linux-i2c <linux-i2c@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Bartosz Golaszewski <brgl@...ev.pl>
Subject: Re: [PATCH] eeprom: at24: don't use the default regmap locking

2017-12-03 22:47 GMT+01:00 Bartosz Golaszewski <brgl@...ev.pl>:
> We need to always wait for the last write to complete and we want the
> regmap to be protected from concurrent access during that wait. That
> makes using the regmap's default locking impossible and we're
> protecting it with an external mutex.
>
> Set an empty function as the callback for regmap's lock and unlock
> routines so that it doesn't allocate any internal resources for
> unnecessary locking.
>
> Signed-off-by: Bartosz Golaszewski <brgl@...ev.pl>
> ---
> This is a temporary solution - I'm working on a patch extending the
> regmap framework with locking policy options, which will allow users
> to manually lock & unlock regmaps if needed or disable locking at all.
>
>  drivers/misc/eeprom/at24.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
>
> diff --git a/drivers/misc/eeprom/at24.c b/drivers/misc/eeprom/at24.c
> index 625b00166117..34bc394a9c14 100644
> --- a/drivers/misc/eeprom/at24.c
> +++ b/drivers/misc/eeprom/at24.c
> @@ -498,14 +498,23 @@ static unsigned int at24_get_offset_adj(u8 flags, unsigned int byte_len)
>         }
>  }
>
> +static void at24_regmap_lock_unlock_none(void *map)
> +{
> +
> +}
> +
>  static const struct regmap_config regmap_config_8 = {
>         .reg_bits = 8,
>         .val_bits = 8,
> +       .lock = at24_regmap_lock_unlock_none,
> +       .unlock = at24_regmap_lock_unlock_none,
>  };
>
>  static const struct regmap_config regmap_config_16 = {
>         .reg_bits = 16,
>         .val_bits = 8,
> +       .lock = at24_regmap_lock_unlock_none,
> +       .unlock = at24_regmap_lock_unlock_none,
>  };
>
>  static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id)
> --
> 2.15.1
>

There were no comments. I applied this patch. These changes will be
removed in 4.17 when we'll enable the newly added disable_locking
variable in regmap config.

Bartosz