linux-kernel - Re: [RESEND PATCH 05/14] eeprom: at24: hide the read/write loop behind a macro

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Message-ID: <20160715122429.GA2620@tetsubishi>
Date:	Fri, 15 Jul 2016 21:24:30 +0900
From:	Wolfram Sang <wsa@...-dreams.de>
To:	Bartosz Golaszewski <bgolaszewski@...libre.com>
Cc:	linux-i2c <linux-i2c@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Andrew Lunn <andrew@...n.ch>,
	Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
	Maxime Ripard <maxime.ripard@...e-electrons.com>,
	GregKH <greg@...ah.com>
Subject: Re: [RESEND PATCH 05/14] eeprom: at24: hide the read/write loop
 behind a macro

> +/*
> + * Both reads and writes fail if the previous write didn't complete yet. This
> + * macro loops a few times waiting at least long enough for one entire page
> + * write to work.
> + *
> + * It takes two parameters: a variable in which the future timeout in jiffies
> + * will be stored and a temporary variable holding the time of the last
> + * iteration of processing the request. Both should be unsigned integers
> + * holding at least 32 bits.
> + */
> +#define loop_until_timeout(tout, op_time)				\
> +	for (tout = jiffies + msecs_to_jiffies(write_timeout),		\
> +		op_time = jiffies;					\
> +	     time_before(op_time, tout);				\
> +	     usleep_range(1000, 1500), op_time = jiffies)

There is one subtle change coming with this change: the do-while loop is
guaranteed to run at least once while the for-loop doesn't.


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