linux-kernel - Re: [PATCH] Introduce an ability to specify microseconds bus scanning intervals in w1 core

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Message-ID: <552D4B21.4020803@infradead.org>
Date:	Tue, 14 Apr 2015 10:15:13 -0700
From:	Randy Dunlap <rdunlap@...radead.org>
To:	Dmitry Khromov <dk@...logic.net>, linux-kernel@...r.kernel.org
CC:	gregkh@...uxfoundation.org, Evgeniy Polyakov <zbr@...emap.net>
Subject: Re: [PATCH] Introduce an ability to specify microseconds bus scanning
 intervals in w1 core

On 04/14/15 00:40, Dmitry Khromov wrote:
> DS1990* "iButtons" and compatible RFID card readers commonly found at
> physical access control systems are usually attached/generate presence
> for as short as 100 ms - hence the tens-to-hundreds milliseconds scan
> intervals are required.
> 
> Tested on Raspberry Pi model B+ with DS2482-100 bus master,
> tens-of-milliseconds intervals are easily achieved without significant
> CPU load (and with unknown accuracy), and though I doubt
> microseconds-scale intervals are really feasible in terms of practical
> use and underlying buses timings, I believe it makes sense to give the
> ability of using them to those willing to try.
> 
> Signed-off-by: Dmitry Khromov <dk@...logic.net>
> Acked-by: Evgeniy Polyakov <zbr@...emap.net>
> 
>  drivers/w1/w1.c | 17 ++++++++++++++++-
>  1 file changed, 16 insertions(+), 1 deletion(-)
> ---
> diff --git a/drivers/w1/w1.c b/drivers/w1/w1.c
> index 181f41c..73b4e2d 100644
> --- a/drivers/w1/w1.c
> +++ b/drivers/w1/w1.c
> @@ -46,11 +46,15 @@ MODULE_AUTHOR("Evgeniy Polyakov <zbr@...emap.net>");
>  MODULE_DESCRIPTION("Driver for 1-wire Dallas network protocol.");
>  
>  static int w1_timeout = 10;
> +static int w1_timeout_us = 0;
>  int w1_max_slave_count = 64;
>  int w1_max_slave_ttl = 10;
>  
>  module_param_named(timeout, w1_timeout, int, 0);
>  MODULE_PARM_DESC(timeout, "time in seconds between automatic slave searches");
> +module_param_named(timeout_us, w1_timeout_us, int, 0);
> +MODULE_PARM_DESC(timeout, "time in microseconds between automatic slave"
> +                         "searches");

The description string needs a space between "slave" and "searches".

>  /* A search stops when w1_max_slave_count devices have been found in that
>   * search.  The next search will start over and detect the same set of devices
>   * on a static 1-wire bus.  Memory is not allocated based on this number, just


-- 
~Randy
--
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