Re: [PATCH RESEND v2 1/7] mfd: cros_ec: Use fixed size arrays to transfer data with the EC

[Lee Jones <lee.jones@linaro.org>]

On Fri, 02 Jan 2015, Javier Martinez Canillas wrote:

> The struct cros_ec_command will be used as an ioctl() argument for the
> API to control the ChromeOS EC from user-space. So the data structure
> has to be 64-bit safe to make it compatible between 32 and 64 avoiding
> the need for a compat ioctl interface. Since pointers are self-aligned
> to different byte boundaries, use fixed size arrays instead of pointers
> for transferring ingoing and outgoing data with the Embedded Controller.
> 
> Also, re-arrange struct members by decreasing alignment requirements to
> reduce the needing padding size.
> 
> Signed-off-by: Javier Martinez Canillas <javier.martinez@collabora.co.uk>
> ---
> 
> Hello,
> 
> I choose EC_PROTO2_MAX_PARAM_SIZE as the maximum length for the input and
> output buffers since I see that is what is assumed in the cros_ec driver
> that is the maximum lengths. But the downstream kernel has also suppport
> for the EC host command protocol v3 even though there is currently no bus
> specific code to handle v3 packets. So I wonder if this is a good max len
> or if a different size should be used instead.
> 
> Best regards,
> Javier
> 
> Changes since v1: None, new patch
> 
>  drivers/i2c/busses/i2c-cros-ec-tunnel.c | 51 +++++++--------------------------
>  drivers/input/keyboard/cros_ec_keyb.c   | 13 +++++----
>  drivers/mfd/cros_ec.c                   | 15 +++++-----
>  include/linux/mfd/cros_ec.h             |  8 +++---
>  4 files changed, 29 insertions(+), 58 deletions(-)

Looks okay to me, but I'd be happy with some more reviews from the
Chrome guys.  I would especially like some knowledgeable type to
answer your EC_PROTO2_MAX_PARAM_SIZE question.  If no one does, I
guess it can always be changed later.

Acked-by: Lee Jones <lee.jones@linaro.org>

> diff --git a/drivers/i2c/busses/i2c-cros-ec-tunnel.c b/drivers/i2c/busses/i2c-cros-ec-tunnel.c
> index 875c22a..fa8dedd 100644
> --- a/drivers/i2c/busses/i2c-cros-ec-tunnel.c
> +++ b/drivers/i2c/busses/i2c-cros-ec-tunnel.c
> @@ -182,72 +182,41 @@ static int ec_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg i2c_msgs[],
>  	const u16 bus_num = bus->remote_bus;
>  	int request_len;
>  	int response_len;
> -	u8 *request = NULL;
> -	u8 *response = NULL;
>  	int result;
> -	struct cros_ec_command msg;
> +	struct cros_ec_command msg = { };
>  
>  	request_len = ec_i2c_count_message(i2c_msgs, num);
>  	if (request_len < 0) {
>  		dev_warn(dev, "Error constructing message %d\n", request_len);
> -		result = request_len;
> -		goto exit;
> +		return request_len;
>  	}
> +
>  	response_len = ec_i2c_count_response(i2c_msgs, num);
>  	if (response_len < 0) {
>  		/* Unexpected; no errors should come when NULL response */
>  		dev_warn(dev, "Error preparing response %d\n", response_len);
> -		result = response_len;
> -		goto exit;
> -	}
> -
> -	if (request_len <= ARRAY_SIZE(bus->request_buf)) {
> -		request = bus->request_buf;
> -	} else {
> -		request = kzalloc(request_len, GFP_KERNEL);
> -		if (request == NULL) {
> -			result = -ENOMEM;
> -			goto exit;
> -		}
> -	}
> -	if (response_len <= ARRAY_SIZE(bus->response_buf)) {
> -		response = bus->response_buf;
> -	} else {
> -		response = kzalloc(response_len, GFP_KERNEL);
> -		if (response == NULL) {
> -			result = -ENOMEM;
> -			goto exit;
> -		}
> +		return response_len;
>  	}
>  
> -	result = ec_i2c_construct_message(request, i2c_msgs, num, bus_num);
> +	result = ec_i2c_construct_message(msg.outdata, i2c_msgs, num, bus_num);
>  	if (result)
> -		goto exit;
> +		return result;
>  
>  	msg.version = 0;
>  	msg.command = EC_CMD_I2C_PASSTHRU;
> -	msg.outdata = request;
>  	msg.outsize = request_len;
> -	msg.indata = response;
>  	msg.insize = response_len;
>  
>  	result = cros_ec_cmd_xfer(bus->ec, &msg);
>  	if (result < 0)
> -		goto exit;
> +		return result;
>  
> -	result = ec_i2c_parse_response(response, i2c_msgs, &num);
> +	result = ec_i2c_parse_response(msg.indata, i2c_msgs, &num);
>  	if (result < 0)
> -		goto exit;
> +		return result;
>  
>  	/* Indicate success by saying how many messages were sent */
> -	result = num;
> -exit:
> -	if (request != bus->request_buf)
> -		kfree(request);
> -	if (response != bus->response_buf)
> -		kfree(response);
> -
> -	return result;
> +	return num;
>  }
>  
>  static u32 ec_i2c_functionality(struct i2c_adapter *adap)
> diff --git a/drivers/input/keyboard/cros_ec_keyb.c b/drivers/input/keyboard/cros_ec_keyb.c
> index ffa989f..769f8f7 100644
> --- a/drivers/input/keyboard/cros_ec_keyb.c
> +++ b/drivers/input/keyboard/cros_ec_keyb.c
> @@ -148,16 +148,19 @@ static void cros_ec_keyb_process(struct cros_ec_keyb *ckdev,
>  
>  static int cros_ec_keyb_get_state(struct cros_ec_keyb *ckdev, uint8_t *kb_state)
>  {
> +	int ret;
>  	struct cros_ec_command msg = {
> -		.version = 0,
>  		.command = EC_CMD_MKBP_STATE,
> -		.outdata = NULL,
> -		.outsize = 0,
> -		.indata = kb_state,
>  		.insize = ckdev->cols,
>  	};
>  
> -	return cros_ec_cmd_xfer(ckdev->ec, &msg);
> +	ret = cros_ec_cmd_xfer(ckdev->ec, &msg);
> +	if (ret < 0)
> +		return ret;
> +
> +	memcpy(kb_state, msg.indata, ckdev->cols);
> +
> +	return 0;
>  }
>  
>  static irqreturn_t cros_ec_keyb_irq(int irq, void *data)
> diff --git a/drivers/mfd/cros_ec.c b/drivers/mfd/cros_ec.c
> index fc0c81e..c872e1b 100644
> --- a/drivers/mfd/cros_ec.c
> +++ b/drivers/mfd/cros_ec.c
> @@ -74,15 +74,11 @@ int cros_ec_cmd_xfer(struct cros_ec_device *ec_dev,
>  	ret = ec_dev->cmd_xfer(ec_dev, msg);
>  	if (msg->result == EC_RES_IN_PROGRESS) {
>  		int i;
> -		struct cros_ec_command status_msg;
> -		struct ec_response_get_comms_status status;
> +		struct cros_ec_command status_msg = { };
> +		struct ec_response_get_comms_status *status;
>  
> -		status_msg.version = 0;
>  		status_msg.command = EC_CMD_GET_COMMS_STATUS;
> -		status_msg.outdata = NULL;
> -		status_msg.outsize = 0;
> -		status_msg.indata = (uint8_t *)&status;
> -		status_msg.insize = sizeof(status);
> +		status_msg.insize = sizeof(*status);
>  
>  		/*
>  		 * Query the EC's status until it's no longer busy or
> @@ -98,7 +94,10 @@ int cros_ec_cmd_xfer(struct cros_ec_device *ec_dev,
>  			msg->result = status_msg.result;
>  			if (status_msg.result != EC_RES_SUCCESS)
>  				break;
> -			if (!(status.flags & EC_COMMS_STATUS_PROCESSING))
> +
> +			status = (struct ec_response_get_comms_status *)
> +				 status_msg.indata;
> +			if (!(status->flags & EC_COMMS_STATUS_PROCESSING))
>  				break;
>  		}
>  	}
> diff --git a/include/linux/mfd/cros_ec.h b/include/linux/mfd/cros_ec.h
> index 0e166b9..71675b1 100644
> --- a/include/linux/mfd/cros_ec.h
> +++ b/include/linux/mfd/cros_ec.h
> @@ -38,20 +38,20 @@ enum {
>  /*
>   * @version: Command version number (often 0)
>   * @command: Command to send (EC_CMD_...)
> - * @outdata: Outgoing data to EC
>   * @outsize: Outgoing length in bytes
> - * @indata: Where to put the incoming data from EC
>   * @insize: Max number of bytes to accept from EC
>   * @result: EC's response to the command (separate from communication failure)
> + * @outdata: Outgoing data to EC
> + * @indata: Where to put the incoming data from EC
>   */
>  struct cros_ec_command {
>  	uint32_t version;
>  	uint32_t command;
> -	uint8_t *outdata;
>  	uint32_t outsize;
> -	uint8_t *indata;
>  	uint32_t insize;
>  	uint32_t result;
> +	uint8_t outdata[EC_PROTO2_MAX_PARAM_SIZE];
> +	uint8_t indata[EC_PROTO2_MAX_PARAM_SIZE];
>  };
>  
>  /**

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