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

Romain Gantois
2025-05-05T15:58:06Z

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Hi Cosmin,

On Monday, 28 April 2025 12:25:13 CEST Cosmin Tanislav 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_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 */

I would suggest clarifying a bit more what "dynamic mapping" means in this
doc. Maybe something like "ATR does not support on-the-fly modifications of its
translation table, use static mappings". IMO this will make it easier for
people who don't have the full technical context of this series and want to
understand what the flag is for.

Everything else looks good to me.

Thanks,

--
Romain Gantois, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

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