linux-kernel - Re: [PATCH] i3c: master: Avoid sending DISEC command with old device address.

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Message-ID: <ZsSs6W8ds67NZqRL@lizhi-Precision-Tower-5810>
Date: Tue, 20 Aug 2024 10:49:13 -0400
From: Frank Li <Frank.li@....com>
To: nxf24178 <ravindra.yashvant.shinde@....com>
Cc: Alexandre Belloni <alexandre.belloni@...tlin.com>,
	"moderated list:I3C SUBSYSTEM" <linux-i3c@...ts.infradead.org>,
	open list <linux-kernel@...r.kernel.org>, imx@...ts.linux.dev
Subject: Re: [PATCH] i3c: master: Avoid sending DISEC command with old device
 address.

On Tue, Aug 20, 2024 at 10:08:17AM +0530, nxf24178 wrote:

Avoid use nxp nxf24178 as your name, please update it with your real name.

> When a new device hotjoins, a new dynamic address is assigned.
> i3c_master_add_i3c_dev_locked() identifies that the device was previously
> attached to the bus and locates the olddev.
>
> i3c_master_add_i3c_dev_locked()
> {
>     ...
>     olddev = i3c_master_search_i3c_dev_duplicate(newdev);
>     ...
>     if (olddev) {
>         enable_ibi = true;
>         ...
>     }
>     i3c_dev_free_ibi_locked(olddev);
>     ^^^^^^^^
>     This function internally calls i3c_dev_disable_ibi_locked(addr)
>     function causing to send DISEC command with old Address.
>
>     The olddev should not receive any commands on the i3c bus as it
>     does not exist and has been assigned a new address. This will
>     result in NACK or timeout. So, update the olddev->ibi->enabled
>     flag to false to avoid DISEC with OldAddr.
>     ...
> }
>
> Signed-off-by: Ravindra Yashvant Shinde <ravindra.yashvant.shinde@....com>
> ---
>  drivers/i3c/master.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/drivers/i3c/master.c b/drivers/i3c/master.c
> index 7028f03c2c42..07ccb2c00074 100644
> --- a/drivers/i3c/master.c
> +++ b/drivers/i3c/master.c
> @@ -2042,6 +2042,7 @@ int i3c_master_add_i3c_dev_locked(struct i3c_master_controller *master,
>  			if (olddev->ibi->enabled) {
>  				enable_ibi = true;
>  				i3c_dev_disable_ibi_locked(olddev);
> +				olddev->ibi->enabled = false;
>  			}

you can set olddev->ibi->enable = false unconditional. and add comments
about why set it to false here.

Frank

>
>  			i3c_dev_free_ibi_locked(olddev);
> --
> 2.46.0
>