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

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Message-ID: <20250430163613.187a0504@booty>
Date: Wed, 30 Apr 2025 16:36:13 +0200
From: Luca Ceresoli <luca.ceresoli@...tlin.com>
To: Cosmin Tanislav <demonsingur@...il.com>
Cc: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>, Wolfram Sang
 <wsa+renesas@...g-engineering.com>, Mauro Carvalho Chehab
 <mchehab@...nel.org>, Romain Gantois <romain.gantois@...tlin.com>, Arnd
 Bergmann <arnd@...db.de>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-media@...r.kernel.org
Subject: Re: [PATCH v4 8/9] i2c: atr: add static flag

On Mon, 28 Apr 2025 13:25:13 +0300
Cosmin Tanislav <demonsingur@...il.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@...il.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
https://bootlin.com