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Date: Wed, 2 Jun 2021 04:57:25 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: Joe Perches <joe@...ches.com>
Cc: Jean Delvare <jdelvare@...e.com>,
Navin Sankar Velliangiri <navin@...umiz.com>,
linux-hwmon@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] hwmon: sht4x: Fix sht4x_read_values return value
On Sat, May 29, 2021 at 02:13:52AM -0700, Joe Perches wrote:
> Kernel doc for sht4x_read_values() shows 0 on success, 1 on failure but
> the return value on success is actually always positive as it is set to
> SHT4X_RESPONSE_LENGTH by a successful call to i2c_master_recv().
>
> Miscellanea:
>
> o Update the kernel doc for sht4x_read_values to 0 for success or -ERRNO
> o Remove incorrectly used kernel doc /** header for other _read functions
> o Typo fix succesfull->successful
> o Reverse a test to unindent a block and use goto unlock
> o Declare cmd[SHT4X_CMD_LEN] rather than cmd[]
>
> At least for gcc 10.2, object size is reduced a tiny bit.
>
> $ size drivers/hwmon/sht4x.o*
> text data bss dec hex filename
> 1752 404 256 2412 96c drivers/hwmon/sht4x.o.new
> 1825 404 256 2485 9b5 drivers/hwmon/sht4x.o.old
>
> Signed-off-by: Joe Perches <joe@...ches.com>
Thanks, applied.
Guenter
> ---
>
> compiled, untested, no hardware
>
> drivers/hwmon/sht4x.c | 95 ++++++++++++++++++++++++---------------------------
> 1 file changed, 45 insertions(+), 50 deletions(-)
>
> diff --git a/drivers/hwmon/sht4x.c b/drivers/hwmon/sht4x.c
> index 1dc51ee2a72ba..09c2a0b064444 100644
> --- a/drivers/hwmon/sht4x.c
> +++ b/drivers/hwmon/sht4x.c
> @@ -67,7 +67,7 @@ struct sht4x_data {
> /**
> * sht4x_read_values() - read and parse the raw data from the SHT4X
> * @sht4x_data: the struct sht4x_data to use for the lock
> - * Return: 0 if succesfull, 1 if not
> + * Return: 0 if successful, -ERRNO if not
> */
> static int sht4x_read_values(struct sht4x_data *data)
> {
> @@ -75,51 +75,53 @@ static int sht4x_read_values(struct sht4x_data *data)
> u16 t_ticks, rh_ticks;
> unsigned long next_update;
> struct i2c_client *client = data->client;
> - u8 crc, raw_data[SHT4X_RESPONSE_LENGTH],
> - cmd[] = {SHT4X_CMD_MEASURE_HPM};
> + u8 crc;
> + u8 cmd[SHT4X_CMD_LEN] = {SHT4X_CMD_MEASURE_HPM};
> + u8 raw_data[SHT4X_RESPONSE_LENGTH];
>
> mutex_lock(&data->lock);
> next_update = data->last_updated +
> msecs_to_jiffies(data->update_interval);
> - if (!data->valid || time_after(jiffies, next_update)) {
> - ret = i2c_master_send(client, cmd, SHT4X_CMD_LEN);
> - if (ret < 0)
> - goto unlock;
> -
> - usleep_range(SHT4X_MEAS_DELAY,
> - SHT4X_MEAS_DELAY + SHT4X_DELAY_EXTRA);
> -
> - ret = i2c_master_recv(client, raw_data, SHT4X_RESPONSE_LENGTH);
> - if (ret != SHT4X_RESPONSE_LENGTH) {
> - if (ret >= 0)
> - ret = -ENODATA;
> -
> - goto unlock;
> - }
> -
> - t_ticks = raw_data[0] << 8 | raw_data[1];
> - rh_ticks = raw_data[3] << 8 | raw_data[4];
> -
> - crc = crc8(sht4x_crc8_table, &raw_data[0], SHT4X_WORD_LEN, CRC8_INIT_VALUE);
> - if (crc != raw_data[2]) {
> - dev_err(&client->dev, "data integrity check failed\n");
> - ret = -EIO;
> - goto unlock;
> - }
> -
> - crc = crc8(sht4x_crc8_table, &raw_data[3], SHT4X_WORD_LEN, CRC8_INIT_VALUE);
> - if (crc != raw_data[5]) {
> - dev_err(&client->dev, "data integrity check failed\n");
> - ret = -EIO;
> - goto unlock;
> - }
> -
> - data->temperature = ((21875 * (int32_t)t_ticks) >> 13) - 45000;
> - data->humidity = ((15625 * (int32_t)rh_ticks) >> 13) - 6000;
> - data->last_updated = jiffies;
> - data->valid = true;
> +
> + if (data->valid && time_before_eq(jiffies, next_update))
> + goto unlock;
> +
> + ret = i2c_master_send(client, cmd, SHT4X_CMD_LEN);
> + if (ret < 0)
> + goto unlock;
> +
> + usleep_range(SHT4X_MEAS_DELAY, SHT4X_MEAS_DELAY + SHT4X_DELAY_EXTRA);
> +
> + ret = i2c_master_recv(client, raw_data, SHT4X_RESPONSE_LENGTH);
> + if (ret != SHT4X_RESPONSE_LENGTH) {
> + if (ret >= 0)
> + ret = -ENODATA;
> + goto unlock;
> + }
> +
> + t_ticks = raw_data[0] << 8 | raw_data[1];
> + rh_ticks = raw_data[3] << 8 | raw_data[4];
> +
> + crc = crc8(sht4x_crc8_table, &raw_data[0], SHT4X_WORD_LEN, CRC8_INIT_VALUE);
> + if (crc != raw_data[2]) {
> + dev_err(&client->dev, "data integrity check failed\n");
> + ret = -EIO;
> + goto unlock;
> }
>
> + crc = crc8(sht4x_crc8_table, &raw_data[3], SHT4X_WORD_LEN, CRC8_INIT_VALUE);
> + if (crc != raw_data[5]) {
> + dev_err(&client->dev, "data integrity check failed\n");
> + ret = -EIO;
> + goto unlock;
> + }
> +
> + data->temperature = ((21875 * (int32_t)t_ticks) >> 13) - 45000;
> + data->humidity = ((15625 * (int32_t)rh_ticks) >> 13) - 6000;
> + data->last_updated = jiffies;
> + data->valid = true;
> + ret = 0;
> +
> unlock:
> mutex_unlock(&data->lock);
> return ret;
> @@ -132,19 +134,14 @@ static ssize_t sht4x_interval_write(struct sht4x_data *data, long val)
> return 0;
> }
>
> -/**
> - * sht4x_interval_read() - read the minimum poll interval
> - * in milliseconds
> - */
> +/* sht4x_interval_read() - read the minimum poll interval in milliseconds */
> static size_t sht4x_interval_read(struct sht4x_data *data, long *val)
> {
> *val = data->update_interval;
> return 0;
> }
>
> -/**
> - * sht4x_temperature1_read() - read the temperature in millidegrees
> - */
> +/* sht4x_temperature1_read() - read the temperature in millidegrees */
> static int sht4x_temperature1_read(struct sht4x_data *data, long *val)
> {
> int ret;
> @@ -158,9 +155,7 @@ static int sht4x_temperature1_read(struct sht4x_data *data, long *val)
> return 0;
> }
>
> -/**
> - * sht4x_humidity1_read() - read a relative humidity in millipercent
> - */
> +/* sht4x_humidity1_read() - read a relative humidity in millipercent */
> static int sht4x_humidity1_read(struct sht4x_data *data, long *val)
> {
> int ret;
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