Re: [PATCH v4 2/6] i3c: master: pre-reserve boardinfo->init_dyn_addr when available

[Boris Brezillon <boris.brezillon@collabora.com>]

On Tue, 10 Dec 2019 11:14:58 +0100
Przemysław Gaj <pgaj@cadence.com> wrote:

> It may be the case that SETDASA fails for some reason. Reserve
> ->init_dyn_addr when it's defined to prevent assigning this address  
> to another slave device. This way when device shows up we don't
> have to re-assign addresses.
> 
> Signed-off-by: Przemysław Gaj <pgaj@cadence.com>
> ---
>  drivers/i3c/master.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/i3c/master.c b/drivers/i3c/master.c
> index 5c06c41e6660..fab6e0609fca 100755
> --- a/drivers/i3c/master.c
> +++ b/drivers/i3c/master.c
> @@ -1263,7 +1263,8 @@ static void i3c_master_put_i3c_addrs(struct i3c_dev_desc *dev)
>  					     I3C_ADDR_SLOT_FREE);
>  
>  	if (dev->boardinfo && dev->boardinfo->init_dyn_addr)
> -		i3c_bus_set_addr_slot_status(&master->bus, dev->info.dyn_addr,
> +		i3c_bus_set_addr_slot_status(&master->bus,
> +					     dev->boardinfo->init_dyn_addr,
>  					     I3C_ADDR_SLOT_FREE);

Should be fixed in a separate patch, or at least mentioned in the
commit message.

>  }
>  
> @@ -1675,6 +1676,11 @@ static int i3c_master_bus_init(struct i3c_master_controller *master)
>  				ret = -EBUSY;
>  				goto err_detach_devs;
>  			}
> +
> +			/* Reserve the slot. */
> +			i3c_bus_set_addr_slot_status(&master->bus,
> +						     i3cboardinfo->init_dyn_addr,
> +						     I3C_ADDR_SLOT_I3C_DEV);

Looks like the "reserve/release init_dyn_addr slot" logic is
asymmetric. I wonder if that's not a problem. Can't we end up in a
situation where the ->init_dyn_addr is released (when SETDASA() fails)
and then re-used without being reserved (when the device is later
discovered through a regular DAA)?

So maybe I was wrong and we should indeed reserve the address in the
i3c_master_get_i3c_addrs() path.

>  		}
>  
>  		i3cdev = i3c_master_alloc_i3c_dev(master, &info);


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