Re: [PATCH v4 8/9] i2c: atr: add static flag

Luca Ceresoli
2025-04-30T14:36:23Z

On Mon, 28 Apr 2025 13:25:13 +0300
Cosmin Tanislav <demonsingur@gmail.com> wrote:

> Some I2C ATRs do not support dynamic remapping, only static mapping
> of direct children.
>
> Add a new flag that prevents old mappings to be replaced or new mappings
> to be created in the alias finding code paths.
>
> Signed-off-by: Cosmin Tanislav <demonsingur@gmail.com>
> ---
> drivers/i2c/i2c-atr.c | 6 +++++-
> include/linux/i2c-atr.h | 3 +++
> 2 files changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/i2c/i2c-atr.c b/drivers/i2c/i2c-atr.c
> index e2350fcf3d68..721dd680f2ac 100644
> --- a/drivers/i2c/i2c-atr.c
> +++ b/drivers/i2c/i2c-atr.c
> @@ -341,12 +341,16 @@ i2c_atr_create_mapping_by_addr(struct i2c_atr_chan *chan, u16 addr)
> static struct i2c_atr_alias_pair *
> i2c_atr_get_mapping_by_addr(struct i2c_atr_chan *chan, u16 addr)
> {
> + struct i2c_atr *atr = chan->atr;
> struct i2c_atr_alias_pair *c2a;
>
> c2a = i2c_atr_find_mapping_by_addr(chan, addr);
> if (c2a)
> return c2a;
>
> + if (atr->flags & I2C_ATR_F_STATIC)
> + return NULL;
> +
> c2a = i2c_atr_create_mapping_by_addr(chan, addr);
> if (c2a)
> return c2a;
> @@ -545,7 +549,7 @@ static int i2c_atr_attach_addr(struct i2c_adapter *adapter,
> mutex_lock(&chan->alias_pairs_lock);
>
> c2a = i2c_atr_create_mapping_by_addr(chan, addr);
> - if (!c2a)
> + if (!c2a && !(atr->flags & I2C_ATR_F_STATIC))
> c2a = i2c_atr_replace_mapping_by_addr(chan, addr);
>
> if (!c2a) {
> diff --git a/include/linux/i2c-atr.h b/include/linux/i2c-atr.h
> index 5082f4dd0e23..7c6a9627191d 100644
> --- a/include/linux/i2c-atr.h
> +++ b/include/linux/i2c-atr.h
> @@ -20,8 +20,11 @@ struct i2c_atr;
>
> /**
> * enum i2c_atr_flags - Flags for an I2C ATR driver
> + *
> + * @I2C_ATR_F_STATIC: ATR does not support dynamic mapping, use static mapping

Maybe add something along the lines of: "mappings can only be
added/removed by the higher level driver via
i2c_atr_attach_addr/i2c_atr_detach_addr"

Other than that, looks good.

Luca

--
Luca Ceresoli, Bootlin
Embedded Linux and Kernel engineering