linux-kernel - Re: [PATCH v2 3/5] hwmon: (tmp102) Improve handling of initial read delay

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Message-ID: <576FD940.4070102@ti.com>
Date:	Sun, 26 Jun 2016 08:31:44 -0500
From:	Nishanth Menon <nm@...com>
To:	Guenter Roeck <linux@...ck-us.net>,
	Jean Delvare <jdelvare@...e.com>
CC:	<linux-hwmon@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	Eduardo Valentin <edubezval@...il.com>,
	Zhang Rui <rui.zhang@...el.com>
Subject: Re: [PATCH v2 3/5] hwmon: (tmp102) Improve handling of initial read
 delay

On 06/25/2016 09:40 PM, Guenter Roeck wrote:
[...]
>  /* convert left adjusted 13-bit TMP102 register value to milliCelsius */
> @@ -78,8 +82,16 @@ static struct tmp102 *tmp102_update_device(struct device *dev)
>  	struct tmp102 *tmp102 = dev_get_drvdata(dev);
>  	struct i2c_client *client = tmp102->client;
>  
> +	/* Is it too early to return a conversion ? */
> +	if (time_before(jiffies, tmp102->ready_time)) {
> +		unsigned long sleeptime = tmp102->ready_time - jiffies;
> +
> +		msleep(jiffies_to_msecs(sleeptime));
> +	}
> +

While msleep can indeed work and simplify, in case of usage for
example with thermal framework, if the data is not ready and we return
-EAGAIN, it lets the thermal framework go and read other sensors
instead of being blocked on the tmp102 conversion of data.

Eduardo, Rui: what is your view on this approach?
Patch: https://patchwork.kernel.org/patch/9198961/

-- 
Regards,
Nishanth Menon