linux-kernel - Re: [PATCH 3/7] Input: libps2 - rework handling of command response

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Message-ID: <ZGZenuKMicegjUsZ@google.com>
Date:   Thu, 18 May 2023 11:21:34 -0600
From:   Raul E Rangel <rrangel@...omium.org>
To:     Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:     linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/7] Input: libps2 - rework handling of command response

On Thu, May 11, 2023 at 11:52:43AM -0700, Dmitry Torokhov wrote:
> It is not entirely correct that libps2 sets PS2_FLAG_CMD1 after
> the device acknowledges each byte sent to the device by the host.
> Rework the code so that PS2_FLAG_CMD1 and PS2_FLAG_CMD are set only once,
> at the beginning of PS/2 command execution.
> 
> Signed-off-by: Dmitry Torokhov <dmitry.torokhov@...il.com>
> ---
>  drivers/input/serio/libps2.c | 18 ++++++++++--------
>  1 file changed, 10 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/input/serio/libps2.c b/drivers/input/serio/libps2.c
> index 399cda0d34f5..d09450eca9a7 100644
> --- a/drivers/input/serio/libps2.c
> +++ b/drivers/input/serio/libps2.c
> @@ -247,14 +247,19 @@ int __ps2_command(struct ps2dev *ps2dev, u8 *param, unsigned int command)
>  
>  	serio_pause_rx(ps2dev->serio);
>  
> +	/* Some mice do not ACK the "get ID" command, prepare to handle this. */
>  	ps2dev->flags = command == PS2_CMD_GETID ? PS2_FLAG_WAITID : 0;
>  	ps2dev->cmdcnt = receive;
> -	if (receive && param)
> -		for (i = 0; i < receive; i++)
> -			ps2dev->cmdbuf[(receive - 1) - i] = param[i];
> +	if (receive) {
> +		/* Indicate that we expect response to the command. */
> +		ps2dev->flags |= PS2_FLAG_CMD | PS2_FLAG_CMD1;
> +		if (param)
> +			for (i = 0; i < receive; i++)
> +				ps2dev->cmdbuf[(receive - 1) - i] = param[i];
> +	}
>  
>  	/*
> -	 * Some devices (Synaptics) peform the reset before
> +	 * Some devices (Synaptics) perform the reset before
>  	 * ACKing the reset command, and so it can take a long
>  	 * time before the ACK arrives.
>  	 */
> @@ -434,11 +439,8 @@ bool ps2_handle_ack(struct ps2dev *ps2dev, u8 data)
>  		return true;
>  	}
>  
> -	if (!ps2dev->nak) {
> +	if (!ps2dev->nak)
>  		ps2dev->flags &= ~PS2_FLAG_NAK;
> -		if (ps2dev->cmdcnt)
> -			ps2dev->flags |= PS2_FLAG_CMD | PS2_FLAG_CMD1;
> -	}
>  
>  	ps2dev->flags &= ~PS2_FLAG_ACK;
>  	wake_up(&ps2dev->wait);
Reviewed-by: Raul E Rangel <rrangel@...omium.org>