[PATCH v1 4/7] regmap: Add reg_seal operation for hardware protection

[Sascha Hauer]

On Fri, May 30, 2025 at 01:41:03PM +0200, Oleksij Rempel wrote:
> Add a new 'reg_seal' operation to the regmap bus interface, along
> with a public API `regmap_seal()`. This is needed for drivers that
> must perform hardware-level "sealing" or permanent write-protection
> on registers/words, a capability not covered by standard regmap
> read/write ops.
> 
> The initial use case is for the STM32 BSEC driver (coming in a
> follow-up patch) to lock One-Time Programmable (OTP) memory words.
> This gives explicit control to make OTP entries permanently read-only
> after programming.
> 
> Signed-off-by: Oleksij Rempel <o.rempel at pengutronix.de>
> ---
>  drivers/base/regmap/internal.h |  2 ++
>  drivers/base/regmap/regmap.c   | 31 +++++++++++++++++++++++++++++++
>  include/linux/regmap.h         | 33 +++++++++++++++++++++++++++++++++
>  3 files changed, 66 insertions(+)
> 
> diff --git a/drivers/base/regmap/internal.h b/drivers/base/regmap/internal.h
> index 6f6a34edc7a8..f2b95cc6361e 100644
> --- a/drivers/base/regmap/internal.h
> +++ b/drivers/base/regmap/internal.h
> @@ -39,6 +39,8 @@ struct regmap {
>  			unsigned int *val);
>  	int (*reg_write)(void *context, unsigned int reg,
>  			 unsigned int val);
> +	int (*reg_seal)(void *context, unsigned int reg,
> +			unsigned int flags);
>  };
>  
>  struct regmap_field {
> diff --git a/drivers/base/regmap/regmap.c b/drivers/base/regmap/regmap.c
> index 777636c0b319..dc65b9e965ce 100644
> --- a/drivers/base/regmap/regmap.c
> +++ b/drivers/base/regmap/regmap.c
> @@ -81,6 +81,17 @@ static int _regmap_bus_reg_write(void *context, unsigned int reg,
>  	return map->bus->reg_write(map->bus_context, reg, val);
>  }
>  
> +static int _regmap_bus_reg_seal(void *context, unsigned int reg,
> +				unsigned int flags)
> +{
> +	struct regmap *map = context;
> +
> +	if (!map->bus->reg_seal)
> +		return -EOPNOTSUPP;
> +
> +	return map->bus->reg_seal(map->bus_context, reg, flags);
> +}
> +
>  /*
>   * regmap_init - initialize and register a regmap
>   *
> @@ -124,6 +135,9 @@ struct regmap *regmap_init(struct device *dev,
>  		}
>  	}
>  
> +	if (!map->reg_seal)
> +		map->reg_seal = _regmap_bus_reg_seal;

map was just xzalloced, so this check seems unnecessary.

Sascha

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