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Date: Tue, 19 Apr 2011 16:20:15 -0700
From: Randy Dunlap <rdunlap@xenotime.net>
To: james_p_freyensee@linux.intel.com
Cc: gregkh@suse.de, linux-kernel@vger.kernel.org, suhail.ahmed@intel.com,
        christophe.guerard@intel.com
Subject: Re: [PATCH 4/4] n_tracerouter and n_tracesink ldisc additions.
Message-Id: <20110419162015.e4446442.rdunlap@xenotime.net>
In-Reply-To: <1303253889-10074-5-git-send-email-james_p_freyensee@linux.intel.com>
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	<1303253889-10074-5-git-send-email-james_p_freyensee@linux.intel.com>
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On Tue, 19 Apr 2011 15:58:09 -0700 james_p_freyensee@linux.intel.com wrote:

>  drivers/tty/Kconfig         |   31 ++++++
>  drivers/tty/Makefile        |    2 +
>  drivers/tty/n_tracerouter.c |  241 ++++++++++++++++++++++++++++++++++++++++++
>  drivers/tty/n_tracesink.c   |  244 +++++++++++++++++++++++++++++++++++++++++++
>  drivers/tty/n_tracesink.h   |   36 +++++++
>  include/linux/tty.h         |    2 +
>  6 files changed, 556 insertions(+), 0 deletions(-)
>  create mode 100644 drivers/tty/n_tracerouter.c
>  create mode 100644 drivers/tty/n_tracesink.c
>  create mode 100644 drivers/tty/n_tracesink.h
> 
> diff --git a/drivers/tty/Kconfig b/drivers/tty/Kconfig
> index 3fd7199..d1ab9c0 100644
> --- a/drivers/tty/Kconfig
> +++ b/drivers/tty/Kconfig
> @@ -319,3 +319,34 @@ config N_GSM
>  	  This line discipline provides support for the GSM MUX protocol and
>  	  presents the mux as a set of 61 individual tty devices.
>  
> +config TRACE_ROUTER
> +	tristate "Trace data router for MIPI P1149.7 cJTAG standard"
> +	depends on TRACE_SINK
> +	default Y

Don't add default Y misc drivers.

> +	help
> +	  The trace router uses the Linux tty line discipline framework to
> +	  route trace data coming from a tty port (say UART for example) to
> +	  the trace sink line discipline driver and to another tty port(say 
> +	  USB). This is part of a solution for the MIPI P1149.7, compact JTAG,
> +	  standard, which is for debugging mobile devices. The PTI driver in
> +	  drivers/misc/pti.c defines the majority of this MIPI solution.
> +
> +	  You should select this driver if the target kernel is meant for
> +	  a mobile device containing a modem.  Then you will need to select
> +	  "Trace data sink for MIPI P1149.7 cJTAG standard" line discipline
> +	  driver.
> +
> +config TRACE_SINK
> +	tristate "Trace data sink for MIPI P1149.7 cJTAG standard"
> +	default Y

ditto.

> +	help
> +	  The trace sink uses the Linux line discipline framework to receive
> +	  trace data coming from the trace router line discipline driver
> +	  to a user-defined tty port target, like USB.
> +	  This is to provide a way to extract modem trace data on
> +	  devices that do not have a PTI HW module, or just need modem
> +	  trace data to come out of a different HW output port.
> +	  This is part of a solution for the P1149.7, compact JTAG, standard.
> +
> +	  If you select this option, you need to select
> +	  "Trace data router for MIPI P1149.7 cJTAG standard".

> diff --git a/drivers/tty/n_tracerouter.c b/drivers/tty/n_tracerouter.c
> new file mode 100644
> index 0000000..7295799
> --- /dev/null
> +++ b/drivers/tty/n_tracerouter.c
> @@ -0,0 +1,241 @@
> +/*
> + *  n_tracerouter.c - Trace data router through tty space
> + *
> + *  Copyright (C) Intel 2011
> + *
> + * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> + *
> + *  This program is free software; you can redistribute it and/or modify
> + *  it under the terms of the GNU General Public License version 2
> + *  as published by the Free Software Foundation.
> + *
> + *  This program is distributed in the hope that it will be useful,
> + *  but WITHOUT ANY WARRANTY; without even the implied warranty of
> + *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + *  GNU General Public License for more details.
> + *
> + * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> + *
> + * This trace router uses the Linux line discipline framework to route
> + * trace data coming from a HW Modem to a PTI (Parallel Trace Module) port.
> + * The solution is not specific to a HW modem and this line disciple can
> + * be used to route any stream of data in kernel space.
> + * This is part of a solution for the P1149.7, compact JTAG, standard.
> + *
> + */
> +
> +#include <linux/init.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/types.h>
> +#include <linux/ioctl.h>
> +#include <linux/tty.h>
> +#include <linux/tty_ldisc.h>
> +#include <linux/errno.h>
> +#include <linux/string.h>
> +#include <linux/mutex.h>
> +#include <linux/slab.h>
> +#include <asm-generic/bug.h>
> +#include "n_tracesink.h"
> +
> +/* Other ldisc drivers use 65536 which basically means,
> + * 'I can always accept 64k' and flow control is off.
> + * This number is deemed appropriate for this driver.
> + */

Fix multi-line comment style throughout.

> +#define RECEIVE_ROOM	65536
> +#define DRIVERNAME	"n_tracerouter"
> +
> +/* struct to hold private configuration data for this ldisc.
> + * opencalled is used to hold if this ldisc has been opened.
> + * kref_tty holds the tty reference the ldisc sits on top of.
> + */
> +struct tracerouter_data {
> +	u8 opencalled;
> +	struct tty_struct *kref_tty;
> +};
> +static struct tracerouter_data *tr_data;
> +
> +/* lock for when tty reference is being used */
> +static DEFINE_MUTEX(routelock);


> +/* Flush buffer is not impelemented as the ldisc has no internal buffering
> + * so the tty_driver_flush_buffer() is sufficient for this driver's needs.
> + */
> +
> +static struct tty_ldisc_ops tty_ptirouter_ldisc = {
> +	.owner		= THIS_MODULE,
> +	.magic		= TTY_LDISC_MAGIC,
> +	.name		= DRIVERNAME,
> +	.open		= n_tracerouter_open,
> +	.close		= n_tracerouter_close,
> +	.read		= n_tracerouter_read,
> +	.write		= n_tracerouter_write,
> +	.receive_buf	= n_tracerouter_receivebuf
> +};

> diff --git a/drivers/tty/n_tracesink.c b/drivers/tty/n_tracesink.c
> new file mode 100644
> index 0000000..4c40127
> --- /dev/null
> +++ b/drivers/tty/n_tracesink.c
> @@ -0,0 +1,244 @@
> +/*
> + *  n_tracesink.c - Trace data router and sink path through tty space.
> + *
> + *  Copyright (C) Intel 2011
> + *
> + * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> + *
> + *  This program is free software; you can redistribute it and/or modify
> + *  it under the terms of the GNU General Public License version 2
> + *  as published by the Free Software Foundation.
> + *
> + *  This program is distributed in the hope that it will be useful,
> + *  but WITHOUT ANY WARRANTY; without even the implied warranty of
> + *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + *  GNU General Public License for more details.
> + *
> + * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> + *
> + * The trace sink uses the Linux line discipline framework to receive
> + * trace data coming from the PTI source line discipline driver
> + * to a user-desired tty port, like USB.
> + * This is to provide a way to extract modem trace data on
> + * devices that do not have a PTI HW module, or just need modem
> + * trace data to come out of a different HW output port.
> + * This is part of a solution for the P1149.7, compact JTAG, standard.
> + *
> + */
> +
> +#include <linux/init.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/types.h>
> +#include <linux/ioctl.h>
> +#include <linux/tty.h>
> +#include <linux/tty_ldisc.h>
> +#include <linux/errno.h>
> +#include <linux/string.h>
> +#include <asm-generic/bug.h>
> +#include "n_tracesink.h"
> +
> +/* Other ldisc drivers use 65536 which basically means,
> + * 'I can always accept 64k' and flow control is off.
> + * This number is deemed appropriate for this driver.
> + */

Fix multi-line comment style throughout.

> +#define RECEIVE_ROOM	65536
> +#define DRIVERNAME	"n_tracesink"
> +
> +/* there is a quirk with this ldisc is he can write data
> + * to a tty from anyone calling his kernel API, which
> + * meets customer requirements in the drivers/misc/pti.c
> + * project.  So he needs to know when he can and cannot write when
> + * the API is called. In theory, the API can be called
> + * after an init() but before a successful open() which
> + * would crash the system if tty is not checked.
> + */
> +static struct tty_struct *this_tty;
> +static DEFINE_MUTEX(writelock);

> +/* Flush buffer is not impelemented as the ldisc has no internal buffering
> + * so the tty_driver_flush_buffer() is sufficient for this driver's needs.
> + */
> +
> +/*
> + * tty_ldisc function operations for this driver.
> + */
> +static struct tty_ldisc_ops tty_n_tracesink = {
> +	.owner		= THIS_MODULE,
> +	.magic		= TTY_LDISC_MAGIC,
> +	.name		= DRIVERNAME,
> +	.open		= n_tracesink_open,
> +	.close		= n_tracesink_close,
> +	.read		= n_tracesink_read,
> +	.write		= n_tracesink_write
> +};


---
~Randy
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