linux-kernel - Re: [RFC][PATCH] hwmon: add support for Sensirion C1 sensor

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <6190165.D1PKLQQHEK@linux-lqwf.site>
Date:	Fri, 20 Jul 2012 16:03:38 +0200
From:	Oliver Neukum <oneukum@...e.de>
To:	Johannes Winkelmann <johannes.winkelmann@...il.com>
Cc:	linux-kernel@...r.kernel.org, lm-sensors@...sensors.org,
	Jean Delvare <khali@...ux-fr.org>,
	Guenter Roeck <linux@...ck-us.net>,
	Johannes Winkelmann <johannes.winkelmann@...sirion.com>
Subject: Re: [RFC][PATCH] hwmon: add support for Sensirion C1 sensor

On Friday 20 July 2012 14:57:22 Johannes Winkelmann wrote:

> +/* sysfs attributes */
> +static struct shtc1_data *shtc1_update_client(struct device *dev)
> +{
> +	struct i2c_client *client = to_i2c_client(dev);
> +	struct shtc1_data *data = i2c_get_clientdata(client);
> +
> +	char buf[SHTC1_RESPONSE_LENGTH];

Is this used for DMA?

> +	int val;
> +	int ret;
> +
> +	mutex_lock(&data->update_lock);
> +
> +	/*
> +	 * initialize 'ret' in case we had a valid result before, but
> +	 * read too quickly in which case we return the last values
> +	 */
> +	ret = !data->valid;
> +
> +	if (time_after(jiffies, data->last_updated + HZ / 10)
> +	    || !data->valid) {
> +		ret = shtc1_update_values(client, data, buf, sizeof(buf));
> +
> +		if (ret)
> +			goto out;
> +
> +		/*
> +		 * From datasheet:
> +		 *   T = -45 + 175 * ST / 2^16
> +		 *   RH = -10 + 120 * SRH / 2^16
> +		 *
> +		 * Adapted for integer fixed point (3 digit) arithmetic
> +		 */
> +		val = (buf[0] << 8) | buf[1];
> +		data->temperature = ((21875 * val) >> 13) - 45000;
> +		val = (buf[3] << 8) | buf[4];

We have dedicated macros for conversion of endianness.

> +		data->humidity = ((15000 * val) >> 13) - 10000;
> +
> +		data->last_updated = jiffies;
> +		data->valid = 1;
> +	}
> +
> +out:
> +	mutex_unlock(&data->update_lock);
> +
> +	return ret == 0 ? data : NULL;
> +}
	Regards
		Oliver

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/