linux-kernel - Re: [PATCH 1/2] misc: Add Wi2Wi w2sc0004 gps driver

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Date:	Tue, 21 Oct 2014 12:49:31 +0200
From:	Pavel Machek <pavel@....cz>
To:	Marek Belisko <marek@...delico.com>
Cc:	arnd@...db.de, gregkh@...uxfoundation.org, robh+dt@...nel.org,
	pawel.moll@....com, mark.rutland@....com,
	ijc+devicetree@...lion.org.uk, galak@...eaurora.org,
	grant.likely@...aro.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, NeilBrown <neilb@...e.de>,
	"H. Nikolaus Schaller" <hns@...delico.com>
Subject: Re: [PATCH 1/2] misc: Add Wi2Wi w2sc0004 gps driver

Hi!

> --- a/drivers/misc/Kconfig
> +++ b/drivers/misc/Kconfig
> @@ -515,6 +515,16 @@ config VEXPRESS_SYSCFG
>  	  bus. System Configuration interface is one of the possible means
>  	  of generating transactions on this bus.
>  
> +config W2SG0004
> +	tristate "W2SG0004 on/off control"

                           ~~ insert GPS here.
And make it bool if it can't be a module.

> +	depends on GPIOLIB
> +	help
> +	  Enable on/off control of W2SG0004 GPS using a virtual GPIO.
> +	  The virtual GPIO can be connected to a DTR line of a serial
> +	  interface to allow powering up if the /dev/tty$n is opened.
> +	  It also provides a rfkill gps node to control the LNA power.
> +	  NOTE: can't currently be compiled as module, so please choose Y.
> +

> +++ b/drivers/misc/w2sg0004.c
> @@ -0,0 +1,512 @@
> +/*
> + * w2sg0004.c
> + * Virtual GPIO of controlling the w2sg0004 GPS receiver.
> + *
> + * Copyright (C) 2011 Neil Brown <neil@...wn.name>
> + *
> + * This receiver has an ON/OFF pin which must be toggled to
> + * turn the device 'on' or 'off'.  A high->low->high toggle
> + * will switch the device on if it is off, and off if it is on.
> + * It is not possible to directly detect the state of the device.
> + * However when it is on it will send characters on a UART line
> + * regularly.
> + * On the OMAP3, the UART line can also be programmed as a GPIO
> + * on which we can receive interrupts.
> + * So when we want the device to be 'off' we can reprogram
> + * the line, toggle the ON/OFF pin and hope that it is off.
> + * However if an interrupt arrives we know that it is really on
> + * and can toggle again.
> + *
> + * To enable receiving on/off requests we create a gpio_chip
> + * with a single 'output' GPIO.  When it is low, the
> + * GPS is turned off.  When it is high, it is turned on.
> + * This can be configured as the DTR GPIO on the UART which
> + * connects the GPS.  Then whenever the tty is open, the GPS
> + * will be switched on, and whenever it is closed, the GPS will
> + * be switched off.
> + *
> + * In addition we register as a rfkill client so that we can
> + * control the LNA power.
> + *
> + */

GPL?

> +/*
> + * There seems to restrictions on how quickly we can toggle the
> + * on/off line.  data sheets says "two rtc ticks", whatever that means.

"seems to"? data -> Data?

> +enum w2sg_state {
> +	W2SG_IDLE,	/* is not changing state */
> +	W2SG_PULSE,	/* activate on/off impulse */
> +	W2SG_NOPULSE	/* desctivate on/off impulse */
> +};

deactivate.

> +
> +struct gpio_w2sg {
> +	struct		rfkill *rf_kill;
> +	struct		regulator *lna_regulator;
> +	int		lna_blocked;	/* rfkill block gps active */
> +	int		lna_is_off;	/* LNA is currently off */
> +	int		is_on;		/* current state (0/1) */
> +	unsigned long	last_toggle;
> +	unsigned long	backoff;	/* time to wait since last_toggle */
> +	int		on_off_gpio;
> +	int		rx_irq;
> +
> +	struct pinctrl *p;
> +	struct pinctrl_state *default_state;	/* should be UART mode */
> +	struct pinctrl_state *monitor_state;	/* monitor RX as GPIO */
> +	enum w2sg_state	state;
> +	int		requested;	/* requested state (0/1) */
> +	int		suspended;
> +	int		rx_redirected;
> +	spinlock_t	lock;
> +#ifdef CONFIG_GPIOLIB
> +	struct gpio_chip gpio;
> +	const char	*gpio_name[1];
> +#endif

Depends on gpiolib, why ifdef?

Array of names?


> +	rf_kill = rfkill_alloc("GPS", &pdev->dev, RFKILL_TYPE_GPS,
> +				&gpio_w2sg0004_rfkill_ops, gw2sg);

Actually, is rfkill interface right one on GPS? GPS is not supposed to
transmit...

> +	int	gpio_base;	/* (not used by DT) - defines the  gpio.base */


Is non-device tree path still usefull?

									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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