linux-kernel - Re: [RESEND PATCH v7 2/6] mfd: cros_ec: Add cros_ec_cmd_xfer

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Message-ID: <20160411111811.GH8094@x1>
Date:	Mon, 11 Apr 2016 12:18:11 +0100
From:	Lee Jones <lee.jones@...aro.org>
To:	Tomeu Vizoso <tomeu.vizoso@...labora.com>
Cc:	linux-kernel@...r.kernel.org, Sameer Nanda <snanda@...omium.org>,
	Javier Martinez Canillas <javier@....samsung.com>,
	Benson Leung <bleung@...omium.org>,
	Enric Balletbò 
	<enric.balletbo@...labora.co.uk>,
	Vic Yang <victoryang@...omium.org>,
	Stephen Boyd <sboyd@...eaurora.org>,
	Vincent Palatin <vpalatin@...omium.org>,
	Randall Spangler <rspangler@...omium.org>,
	Todd Broch <tbroch@...omium.org>,
	Gwendal Grignou <gwendal@...omium.org>,
	Olof Johansson <olof@...om.net>
Subject: Re: [RESEND PATCH v7 2/6] mfd: cros_ec: Add cros_ec_cmd_xfer_status
 helper

On Tue, 05 Apr 2016, Tomeu Vizoso wrote:

> So that callers of cros_ec_cmd_xfer don't have to repeat boilerplate
> code when checking for errors from the EC side.
> 
> Signed-off-by: Tomeu Vizoso <tomeu.vizoso@...labora.com>
> Reviewed-by: Benson Leung <bleung@...omium.org>
> ---
> 
> Changes in v7: None
> Changes in v6: None
> Changes in v5:
> - Check explicitly for !EC_RES_SUCCESS as suggested by Benson Leung.
> 
> Changes in v4: None
> Changes in v3: None
> Changes in v2: None
> 
>  drivers/platform/chrome/cros_ec_proto.c | 14 ++++++++++++++
>  include/linux/mfd/cros_ec.h             | 18 ++++++++++++++++++
>  2 files changed, 32 insertions(+)
> 
> diff --git a/drivers/platform/chrome/cros_ec_proto.c b/drivers/platform/chrome/cros_ec_proto.c
> index c792e116e621..aaccdde1c9d5 100644
> --- a/drivers/platform/chrome/cros_ec_proto.c
> +++ b/drivers/platform/chrome/cros_ec_proto.c
> @@ -472,3 +472,17 @@ int cros_ec_get_next_event(struct cros_ec_device *ec_dev)
>  		return get_keyboard_state_event(ec_dev);
>  }
>  EXPORT_SYMBOL(cros_ec_get_next_event);
> +
> +int cros_ec_cmd_xfer_status(struct cros_ec_device *ec_dev,
> +			    struct cros_ec_command *msg)
> +{
> +	int ret = cros_ec_cmd_xfer(ec_dev, msg);

I don't really like function calls during declaration time.

If you make the call here, you don't have to leave a pointless '\n'
between it and checking the return value.

> +	if (ret < 0)
> +		dev_err(ec_dev->dev, "Command xfer error (err:%d)\n", ret);
> +	else if (msg->result != EC_RES_SUCCESS)
> +		return -EECRESULT - msg->result;
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL(cros_ec_cmd_xfer_status);
> diff --git a/include/linux/mfd/cros_ec.h b/include/linux/mfd/cros_ec.h
> index ddc935ef1911..e4c4c0480c14 100644
> --- a/include/linux/mfd/cros_ec.h
> +++ b/include/linux/mfd/cros_ec.h
> @@ -40,6 +40,9 @@
>  #define EC_MAX_REQUEST_OVERHEAD		1
>  #define EC_MAX_RESPONSE_OVERHEAD	2
>  
> +/* ec_command return value for non-success result from EC */
> +#define EECRESULT 1000
> +
>  /*
>   * Command interface between EC and AP, for LPC, I2C and SPI interfaces.
>   */
> @@ -250,6 +253,21 @@ int cros_ec_cmd_xfer(struct cros_ec_device *ec_dev,
>  		     struct cros_ec_command *msg);
>  
>  /**
> + * cros_ec_cmd_xfer_status - Send a command to the ChromeOS EC
> + *
> + * This function is identical to cros_ec_cmd_xfer, except it returns succes
> + * status only if both the command was transmitted successfully and the EC
> + * replied with success status. It's not necessary to check msg->result when
> + * using this function.

Is it useful for callers of cros_ec_cmd_xfer() to ever not do this?
If not, why don't you make these changes in cros_ec_cmd_xfer() itself?

> + * @ec_dev: EC device
> + * @msg: Message to write
> + * @return: Num. of bytes transferred on success, <0 on failure
> + */
> +int cros_ec_cmd_xfer_status(struct cros_ec_device *ec_dev,
> +			    struct cros_ec_command *msg);
> +
> +/**
>   * cros_ec_remove - Remove a ChromeOS EC
>   *
>   * Call this to deregister a ChromeOS EC, then clean up any private data.

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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