linux-kernel - Re: [PATCH 1/6] platform/chrome: cros_ec_lpc: MEC access can return error code

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Message-ID: <ZksbzQeR6cDsQz0B@google.com>
Date: Mon, 20 May 2024 17:45:49 +0800
From: Tzung-Bi Shih <tzungbi@...nel.org>
To: Ben Walsh <ben@...nut.com>
Cc: Benson Leung <bleung@...omium.org>, Guenter Roeck <groeck@...omium.org>,
	"Dustin L. Howett" <dustin@...ett.net>,
	Kieran Levin <ktl@...me.work>,
	Thomas Weißschuh <linux@...ssschuh.net>,
	Mario Limonciello <mario.limonciello@....com>,
	chrome-platform@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/6] platform/chrome: cros_ec_lpc: MEC access can return
 error code

On Wed, May 15, 2024 at 06:56:26AM +0100, Ben Walsh wrote:
> diff --git a/drivers/platform/chrome/cros_ec_lpc.c b/drivers/platform/chrome/cros_ec_lpc.c
[...]
> @@ -116,14 +118,19 @@ static u8 cros_ec_lpc_write_bytes(unsigned int offset, unsigned int length,
>   * An instance of the read function of struct lpc_driver_ops, used for the
>   * MEC variant of LPC EC.
>   */
> -static u8 cros_ec_lpc_mec_read_bytes(unsigned int offset, unsigned int length,
> -				     u8 *dest)
> +static int cros_ec_lpc_mec_read_bytes(unsigned int offset, unsigned int length,
> +				      u8 *dest)
>  {
> -	int in_range = cros_ec_lpc_mec_in_range(offset, length);
> +	int in_range;
>  
> -	if (in_range < 0)
> +	if (length == 0)
>  		return 0;
>  
> +	in_range = cros_ec_lpc_mec_in_range(offset, length);
> +
> +	if (in_range < 0)
> +		return in_range;
> +
>  	return in_range ?
>  		cros_ec_lpc_io_bytes_mec(MEC_IO_READ,
>  					 offset - EC_HOST_CMD_REGION0,

The `in_range` change looks irrelevant to the patch.  Or it should rather be
an independent patch if it fixes something.

> @@ -135,14 +142,19 @@ static u8 cros_ec_lpc_mec_read_bytes(unsigned int offset, unsigned int length,
>   * An instance of the write function of struct lpc_driver_ops, used for the
>   * MEC variant of LPC EC.
>   */
> -static u8 cros_ec_lpc_mec_write_bytes(unsigned int offset, unsigned int length,
> -				      const u8 *msg)
> +static int cros_ec_lpc_mec_write_bytes(unsigned int offset, unsigned int length,
> +				       const u8 *msg)
>  {
> -	int in_range = cros_ec_lpc_mec_in_range(offset, length);
> +	int in_range;
>  
> -	if (in_range < 0)
> +	if (length == 0)
>  		return 0;
>  
> +	in_range = cros_ec_lpc_mec_in_range(offset, length);
> +
> +	if (in_range < 0)
> +		return in_range;
> +
>  	return in_range ?
>  		cros_ec_lpc_io_bytes_mec(MEC_IO_WRITE,
>  					 offset - EC_HOST_CMD_REGION0,

Same as above.

> @@ -179,28 +194,41 @@ static int cros_ec_pkt_xfer_lpc(struct cros_ec_device *ec,
[...]
>  	/* Check result */
> -	msg->result = cros_ec_lpc_ops.read(EC_LPC_ADDR_HOST_DATA, 1, &sum);
> +	ret = cros_ec_lpc_ops.read(EC_LPC_ADDR_HOST_DATA, 1, &sum);
> +	if (ret < 0)
> +		goto done;
> +	msg->result = sum;

Even though they are equivalent, `msg->result = ret` looks more intuitive.

> @@ -255,32 +286,47 @@ static int cros_ec_cmd_xfer_lpc(struct cros_ec_device *ec,
[...]
>  	/* Check result */
> -	msg->result = cros_ec_lpc_ops.read(EC_LPC_ADDR_HOST_DATA, 1, &sum);
> +	ret = cros_ec_lpc_ops.read(EC_LPC_ADDR_HOST_DATA, 1, &sum);
> +	if (ret < 0)
> +		goto done;
> +	msg->result = sum;

Same as above.