[PATCH] i3c: Allow OF-alias-based persistent bus numbering

[Ben Dooks]

On 05/04/2023 10:41, Jeremy Kerr wrote:
> Parse the /aliases node to assign any fixed bus numbers, as is done with
> the i2c subsystem. Numbering for non-aliased busses will start after the
> highest fixed bus number.
> 
> This allows an alias node such as:
> 
>      aliases {
>          i3c0 = &bus_a,
> 	i3c4 = &bus_b,
>      };
> 
> to set the numbering for a set of i3c controllers:
> 
>      /* fixed-numbered bus, assigned "i3c-0" */
>      bus_a: i3c-master {
>      };
> 
>      /* another fixed-numbered bus, assigned "i3c-4" */
>      bus_b: i3c-master {
>      };
> 
>      /* dynamic-numbered bus, likely assigned "i3c-5" */
>      bus_c: i3c-master {
>      };
> 
> If no i3c device aliases are present, the numbering will stay as-is,
> starting from 0.
> 
> Signed-off-by: Jeremy Kerr <jk at codeconstruct.com.au>
> ---
>   drivers/i3c/master.c | 30 +++++++++++++++++++++++++-----
>   1 file changed, 25 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/i3c/master.c b/drivers/i3c/master.c
> index af8b9ebaec34..6a3169e4606e 100644
> --- a/drivers/i3c/master.c
> +++ b/drivers/i3c/master.c
> @@ -21,6 +21,7 @@
>   
>   static DEFINE_IDR(i3c_bus_idr);
>   static DEFINE_MUTEX(i3c_core_lock);
> +static int __i3c_first_dynamic_bus_num;
>   
>   /**
>    * i3c_bus_maintenance_lock - Lock the bus for a maintenance operation
> @@ -419,9 +420,9 @@ static void i3c_bus_cleanup(struct i3c_bus *i3cbus)
>   	mutex_unlock(&i3c_core_lock);
>   }
>   
> -static int i3c_bus_init(struct i3c_bus *i3cbus)
> +static int i3c_bus_init(struct i3c_bus *i3cbus, struct device_node *np)

would it be worth passing the struct i3c_master_controller through
this in case other info is needed at a later date? Does ACPI have
anything similar?

>   {
> -	int ret;
> +	int ret, start, end, id = -1;
>   
>   	init_rwsem(&i3cbus->lock);
>   	INIT_LIST_HEAD(&i3cbus->devs.i2c);
> @@ -429,8 +430,19 @@ static int i3c_bus_init(struct i3c_bus *i3cbus)
>   	i3c_bus_init_addrslots(i3cbus);
>   	i3cbus->mode = I3C_BUS_MODE_PURE;
>   
> +	if (np)
> +		id = of_alias_get_id(np, "i3c");
> +
>   	mutex_lock(&i3c_core_lock);
> -	ret = idr_alloc(&i3c_bus_idr, i3cbus, 0, 0, GFP_KERNEL);
> +	if (id >= 0) {
> +		start = id;
> +		end = start + 1;
> +	} else {
> +		start = __i3c_first_dynamic_bus_num;
> +		end = 0;
> +	}
> +
> +	ret = idr_alloc(&i3c_bus_idr, i3cbus, start, end, GFP_KERNEL);
>   	mutex_unlock(&i3c_core_lock);
>   
>   	if (ret < 0)
> @@ -2618,7 +2630,7 @@ int i3c_master_register(struct i3c_master_controller *master,
>   	INIT_LIST_HEAD(&master->boardinfo.i2c);
>   	INIT_LIST_HEAD(&master->boardinfo.i3c);
>   
> -	ret = i3c_bus_init(i3cbus);
> +	ret = i3c_bus_init(i3cbus, master->dev.of_node);
>   	if (ret)
>   		return ret;
>   
> @@ -2846,8 +2858,16 @@ void i3c_dev_free_ibi_locked(struct i3c_dev_desc *dev)
>   
>   static int __init i3c_init(void)
>   {
> -	int res = bus_register_notifier(&i2c_bus_type, &i2cdev_notifier);
> +	int res;
> +
> +	res = of_alias_get_highest_id("i3c");
> +	if (res >= 0) {
> +		mutex_lock(&i3c_core_lock);
> +		__i3c_first_dynamic_bus_num = res + 1;
> +		mutex_unlock(&i3c_core_lock);
> +	}
>   
> +	res = bus_register_notifier(&i2c_bus_type, &i2cdev_notifier);
>   	if (res)
>   		return res;
>