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Date:   Sat, 29 Aug 2020 09:47:58 +0200
From:   Pavel Machek <>
To:     Raul E Rangel <>
Cc:,,, Andy Shevchenko <>,
        Dan Murphy <>,
        Darren Hart <>,
        Jacek Anaszewski <>,
        "Lee, Chun-Yi" <>, Rajat Jain <>,
        Stephen Boyd <>,,,
Subject: Re: [PATCH 1/2] Input: i8042 - Prevent intermixing i8042 commands

On Thu 2020-08-27 13:52:22, Raul E Rangel wrote:
> The i8042_mutex must be held by writers of the AUX and KBD ports, as
> well as users of i8042_command. There were a lot of users of
> i8042_command that were not calling i8042_lock_chip/i8042_unlock_chip.
> This resulted in i8042_commands being issues in between PS/2
> transactions.
> This change moves the mutex lock into i8042_command and removes the
> burden of locking the mutex from the callers.
> It is expected that the i8042_mutex is locked before calling
> i8042_aux_write or i8042_kbd_write. This is currently done by the PS/2
> layer via ps2_begin_command and ps2_end_command. Other modules
> (serio_raw) do not currently lock the mutex, so there is still a
> possibility for intermixed commands.

> @@ -343,10 +330,14 @@ int i8042_command(unsigned char *param, int command)
>  	unsigned long flags;
>  	int retval;
> +	mutex_lock(&i8042_mutex);
> +
>  	spin_lock_irqsave(&i8042_lock, flags);
>  	retval = __i8042_command(param, command);
>  	spin_unlock_irqrestore(&i8042_lock, flags);
> +	 mutex_unlock(&i8042_mutex);
> +
>  	return retval;

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