linux-kernel - Re: [PATCH v2 3/4] iio: common: ssp_sensors: drop conditional optimization for simplicity

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Message-ID: <5e133bba-ee3e-498f-80ea-375dd857c057@baylibre.com>
Date: Mon, 16 Dec 2024 15:57:44 -0600
From: David Lechner <dlechner@...libre.com>
To: Vasileios Amoiridis <vassilisamir@...il.com>, jic23@...nel.org,
 lars@...afoo.de
Cc: krzysztof.kozlowski@...aro.org, nuno.sa@...log.com,
 u.kleine-koenig@...libre.com, abhashkumarjha123@...il.com,
 jstephan@...libre.com, jackoalan@...il.com, k.wrona@...sung.com,
 linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/4] iio: common: ssp_sensors: drop conditional
 optimization for simplicity

On 12/14/24 1:14 PM, Vasileios Amoiridis wrote:
> Drop conditional in favor of always calculating the timestamp value.
> This simplifies the code and allows to drop usage of internal private
> variable "scan_timestamp" of the struct iio_dev.
> 
> Signed-off-by: Vasileios Amoiridis <vassilisamir@...il.com>
> ---
>  drivers/iio/common/ssp_sensors/ssp_iio.c | 9 +++------
>  1 file changed, 3 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/iio/common/ssp_sensors/ssp_iio.c b/drivers/iio/common/ssp_sensors/ssp_iio.c
> index caa404edd9d0..6b86b5315694 100644
> --- a/drivers/iio/common/ssp_sensors/ssp_iio.c
> +++ b/drivers/iio/common/ssp_sensors/ssp_iio.c
> @@ -8,6 +8,8 @@
>  #include <linux/iio/kfifo_buf.h>
>  #include <linux/module.h>
>  #include <linux/slab.h>
> +#include <linux/unaligned.h>
> +#include <linux/units.h>
>  #include "ssp_iio_sensor.h"
>  
>  /**
> @@ -70,7 +72,6 @@ EXPORT_SYMBOL_NS(ssp_common_buffer_postdisable, "IIO_SSP_SENSORS");
>  int ssp_common_process_data(struct iio_dev *indio_dev, void *buf,
>  			    unsigned int len, int64_t timestamp)
>  {
> -	__le32 time;
>  	int64_t calculated_time = 0;
>  	struct ssp_sensor_data *spd = iio_priv(indio_dev);
>  
> @@ -82,11 +83,7 @@ int ssp_common_process_data(struct iio_dev *indio_dev, void *buf,
>  	 */
>  	memcpy(spd->buffer, buf, len);
>  
> -	if (indio_dev->scan_timestamp) {
> -		memcpy(&time, &((char *)buf)[len], SSP_TIME_SIZE);
> -		calculated_time =
> -			timestamp + (int64_t)le32_to_cpu(time) * 1000000;
> -	}
> +	calculated_time = timestamp + get_unaligned_le32(buf + len) * MEGA;

Don't we still need to cast to 64 bit to avoid multiplication overflow?

>  
>  	return iio_push_to_buffers_with_timestamp(indio_dev, spd->buffer,
>  						  calculated_time);