linux-kernel - Re: [PATCH v2 1/1] i3c: master: Avoid sending DISEC command with old device address.

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Message-ID: <3da836dc-d79c-41b9-aa44-06a94b812bbf@quicinc.com>
Date: Thu, 5 Sep 2024 15:25:09 +0530
From: Mukesh Kumar Savaliya <quic_msavaliy@...cinc.com>
To: Ravindra Yashvant Shinde <ravindra.yashvant.shinde@....com>,
        Alexandre
 Belloni <alexandre.belloni@...tlin.com>,
        "moderated list:I3C SUBSYSTEM"
	<linux-i3c@...ts.infradead.org>,
        open list <linux-kernel@...r.kernel.org>
CC: <imx@...ts.linux.dev>, <Frank.Li@....com>
Subject: Re: [PATCH v2 1/1] i3c: master: Avoid sending DISEC command with old
 device address.

Hi Ravindra,


On 8/20/2024 8:49 PM, Ravindra Yashvant Shinde wrote:
> 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.
> 
After  2-3 reads i could understand what exactly you are trying.
Could you please keep the complete commit log here ?

"
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.
"

Make a complete story here, you don't need function to be added here 
since description should make it clear to understand.

> 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
Isn't this the same device who raised HOTJOIN and seeking a new dynamic 
address ? you intend to have no communication with older device address 
right ?
>      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>
> ---
> change from v1 to v2
> - Fixed the author name.
> - Unconditional set to the false & added some comments.
> ---
>   drivers/i3c/master.c | 9 ++++++++-
>   1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/i3c/master.c b/drivers/i3c/master.c
> index 7028f03c2c42..0dd8d1c28d58 100644
> --- a/drivers/i3c/master.c
> +++ b/drivers/i3c/master.c
> @@ -2043,7 +2043,14 @@ int i3c_master_add_i3c_dev_locked(struct i3c_master_controller *master,
>   				enable_ibi = true;
>   				i3c_dev_disable_ibi_locked(olddev);
>   			}
> -
> +			/*
> +			 * 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.
> +			 */
> +			olddev->ibi->enabled = false;
>   			i3c_dev_free_ibi_locked(olddev);
>   		}
>   		mutex_unlock(&olddev->ibi_lock);