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<title>/usr/web/sources/contrib/cross/devgpio.c - Plan 9 from Bell Labs</title>


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<a href="/plan9/">Plan 9 from Bell Labs</a>’s /usr/web/sources/contrib/cross/devgpio.c


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Copyright © 2009 Alcatel-Lucent. 
Distributed under the
<a href="/plan9/license.html">Lucent Public License version 1.02</a>.
 
<a href="/plan9/download.html">Download the Plan 9 distribution.</a>

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/*
* access to GPIO pins.
*/

#include "u.h"
#include "../port/lib.h"
#include "mem.h"
#include "dat.h"
#include "fns.h"
#include "../port/error.h"

enum{
Qrootdir = 0,
Qgpiodir,
Q17,
Q18,
};

static Dirtab gpiorootdir[]={
".", {Qrootdir, 0, QTDIR}, 0, 0555,
"gpio", {Qgpiodir, 0, QTDIR}, 0, 0555,
};

static Dirtab gpiodir[]={
".", {Qgpiodir, 0, QTDIR}, 0, 0555,
"17", {Q17, 0}, 0, 0664,
"18", {Q18, 0}, 0, 0664,
};

enum {
Pin17 = 17,
Pin18 = 18,
Npins,

Output = 0x01,

Off = 0,
On,
};

static int gpiostate[Npins];

extern void gpioout(uint pin, int set);
extern void gpiosel(uint pin, int func);

static void
gpioinit(void)
{
gpiosel(Pin17, Output);
gpiosel(Pin18, Output);
}

static int
gpiogen(Chan *c, char *name, Dirtab *, int, int s, Dir *dp)
{
if ((ulong)c->qid.path == Qrootdir) {
if (s == DEVDOTDOT){
devdir(c, (Qid){Qrootdir, 0, QTDIR}, "#G", 0, eve, 0555, dp);
return 1;
}
return devgen(c, name, gpiorootdir, nelem(gpiorootdir), s, dp);
}
if ((ulong)c->qid.path == Qgpiodir && s == DEVDOTDOT){
devdir(c, (Qid){Qrootdir, 0, QTDIR}, "#G", 0, eve, 0555, dp);
return 1;
}
return devgen(c, name, gpiodir, nelem(gpiodir), s, dp);
}

static long
gpioread(Chan *c, void *a, long n, vlong offset)
{
int pin;
char *status;

if(c->qid.type & QTDIR)
return devdirread(c, a, n, nil, 0, gpiogen);

pin = 0;
switch((ulong)c->qid.path){
case Q17:
pin = Pin17;
break;
case Q18:
pin = Pin18;
break;
default:
error(Ebadarg);
break;
}
status = gpiostate[pin] ? "on" : "off";
return readstr(offset, a, n, status);
}

static long
gpiowrite(Chan*c, void *a, long n, vlong)
{
int state;
char *ch, buf[20];

if (n >= sizeof(buf))
error(Ebadarg);
strncpy(buf, a, sizeof(buf));
buf[sizeof(buf)-1] = '\0';
ch = strrchr(buf, '\n');
if (ch != nil)
*ch = '\0';
state = (strcmp(buf, "on") == 0);
switch((ulong)c->qid.path){
case Q17:
gpiostate[Pin17] = state;
gpioout(Pin17, state);
break;
case Q18:
gpiostate[Pin18] = state;
gpioout(Pin18, state);
break;
default:
error(Ebadarg);
break;
}
return n;
}

static Chan*
gpioattach(char* spec)
{
return devattach('G', spec);
}

static Walkqid*
gpiowalk(Chan* c, Chan *nc, char** name, int nname)
{
return devwalk(c, nc, name, nname, nil, 0, gpiogen);
}

static int
gpiostat(Chan* c, uchar* dp, int n)
{
return devstat(c, dp, n, nil, 0, gpiogen);
}

static Chan*
gpioopen(Chan* c, int omode)
{
return devopen(c, omode, nil, 0, gpiogen);
}

static void
gpioclose(Chan*)
{
}

Dev gpiodevtab = {
'G',
"gpio",

devreset,
gpioinit,
devshutdown,
gpioattach,
gpiowalk,
gpiostat,
gpioopen,
devcreate,
gpioclose,
gpioread,
devbread,
gpiowrite,
devbwrite,
devremove,
devwstat,
};

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