linux-kernel - Re: [PATCH 2/5] drivers/thunderbolt: don't resume switches without uid set

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Date:   Thu, 3 Mar 2022 09:43:38 +0200
From:   Mika Westerberg <mika.westerberg@...ux.intel.com>
To:     Mario Limonciello <mario.limonciello@....com>
Cc:     "open list:THUNDERBOLT DRIVER" <linux-usb@...r.kernel.org>,
        linux-kernel@...r.kernel.org, Sanju.Mehta@....com
Subject: Re: [PATCH 2/5] drivers/thunderbolt: don't resume switches without
 uid set

Hi Mario,

On Wed, Mar 02, 2022 at 04:07:06PM -0600, Mario Limonciello wrote:
> Switches might not have a uid set if the DROM read failed during

That's "Routers" and "UID" :)

Also $subject should have prefix "thunderbolt: " not
"drivers/thunderbolt". Please capitalize the summary too:

  thunderbolt: Do not resume routers if UID is not set

The patch itself looks good to me.

> initialization previously.
> 
> Normally upon resume the uid is re-read to confirm it's the same
> device connected.
> * If the DROM read failed during init but then succeeded during
>   resume it could either be a new device or faulty device
> * If the DROM read failed during init and also failed during resume
>   it might be a different device plugged in all together.
> 
> Detect this situation and prevent re-using the same configuration in
> these cirucmstances.
> 
> Signed-off-by: Mario Limonciello <mario.limonciello@....com>
> ---
>  drivers/thunderbolt/switch.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/thunderbolt/switch.c b/drivers/thunderbolt/switch.c
> index b5fb3e76ed09..294518af4ee4 100644
> --- a/drivers/thunderbolt/switch.c
> +++ b/drivers/thunderbolt/switch.c
> @@ -2980,6 +2980,10 @@ int tb_switch_resume(struct tb_switch *sw)
>  			return err;
>  		}
>  
> +		/* We don't have any way to confirm this was the same device */
> +		if (!sw->uid)
> +			return -ENODEV;
> +
>  		if (tb_switch_is_usb4(sw))
>  			err = usb4_switch_read_uid(sw, &uid);
>  		else
> -- 
> 2.34.1