linux-kernel - Re: [PATCH] i.MX31: mxc-rnga: implement waiting for data in driver

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Message-ID: <4F43AC8D.5090508@hale.at>
Date:	Tue, 21 Feb 2012 15:39:09 +0100
From:	Michael Thalmeier <michael.thalmeier@...e.at>
To:	Fabio Estevam <festevam@...il.com>
CC:	Matt Mackall <mpm@...enic.com>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	linux-arm-kernel@...ts.infradead.org, michael@...lmeier.at,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] i.MX31: mxc-rnga: implement waiting for data in driver

On 2012-02-21 14:29, Fabio Estevam wrote:

> On Tue, Feb 21, 2012 at 10:13 AM, Michael Thalmeier
> <michael.thalmeier@...e.at> wrote:
> 
>> -static int mxc_rnga_data_present(struct hwrng *rng)
>> +static int mxc_rnga_data_present(struct hwrng *rng, int wait)
> 
> This looks good, but ...
> 
>>  {
>> -       int level;
>> +       int level, i;
>>        void __iomem *rng_base = (void __iomem *)rng->priv;
>>
>> -       /* how many random numbers is in FIFO? [0-16] */
>> -       level = ((__raw_readl(rng_base + RNGA_STATUS) &
>> -                       RNGA_STATUS_LEVEL_MASK) >> 8);
>> +       for (i = 0; i < 20; i++) {
> 
> Why the magic "20" here?
> 
> It would be better to add a proper timeout mechanism instead, such as
> time_after(jiffies, timeout)
> 


I am absolutely with you.
The point is only that this is the behaviour of nearly all hw_random
drivers, and I basically just copied it over into this driver.


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