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Date: Wed, 9 Aug 2006 10:02:53 +0000 (GMT)
From: moreau francis <francis_moreau2000@yahoo.fr>
Reply-To: moreau francis <francis_moreau2000@yahoo.fr>
Subject: Re : [HW_RNG] How to use generic rng in kernel space
To: Michael Buesch <mb@bu3sch.de>
Cc: linux-kernel@vger.kernel.org
In-Reply-To: <200608081934.31694.mb@bu3sch.de>
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Michael Buesch wrote:
> On Tuesday 08 August 2006 17:39, moreau francis wrote:
>> Michael Buesch wrote:
>>> So, if you have a special hwrng on your embedded board and you
>>> have some special driver in that board, why not interface
>>> directly from the driver to the hwrng-driver?
>> This is what I'm currently doing. I was just thinking to use the
>> new HW-RNG layer and drop common code...
>>
>>> This is all pretty special case.
>>> In the hwrng-driver you could still additionally do a
>>> hrwng_register() to export the functionality to
>>> userspace, though.
>>>
>> yes I would like to do that but there is a problem: I have no 
>> access to "rng_mutex" to synchronise hw accesses and I'm
>> wondering if there's any issue to use a mutex in driver init
>> code.
> 
> Use your own mutex or spinlock in the data_read callback
> and use that to serialize accesses to the hardware.
> 

I think I miss something there but I need to lock this whole
sequence when reading a random data:

    lock(hwrng);
    rng_data_present();
    rng_data_read();
    unlock(hwrng);

not only data_read callback. To do that I can only use "rng_mutex",
no ?

thanks

Francis