Hi all,
I had to use the GPIO pins of a pl2303hx USB serial chip in a project
and I could not find any information how to control these pins under Linux.
Playing around with the pl2303 driver and a USB analyzer,
it turned out what kind of USB vendor requests shall be sent to control
those pins.
I am not sure if this patch suits to the pl2303 driver, but I am
interested in opinions and comments.
Maybe it can be useful for folks who would like to use the GPIO of this
chip.
To write the register in pl2303hx IC that controls the GPIO pins, use:
pl2303_vendor_write(1, gpio, serial);
where gpio is the register value,
to read the register from the IC use:
pl2303_vendor_read(0x0081, 0, serial, buf);
and the result is in buf[0].
The GPIO control register bits:
0..3: unknown (zero)
4: gp0 output enable (1: gp0 pin is output, 0: gp0 pin is input)
5: gp1 output enable (1: gp1 pin is output, 0: gp1 pin is input)
6: gp0 pin value
7: gp1 pin value
For example writing 0xA0 to the register configures gp0 to input mode,
and gp1 to output high.
The following patch introduces a new module parameter (gpio),
to initialize the GPIO control register of pl2303hx in pl2303_startup,
and a new ioctl to control it from user applications.
Best Regards,
Balint Viragh
Code snippet about using the ioctl:
/** ioctl to write a GPIO register */
#define PL2303_GPIO_SET _IOW('v', 0xac, int)
/** ioctl to read a GPIO register */
#define PL2303_GPIO_GET _IOR('v', 0xac, int)
/** macro function to set direction bit of a gpio pin */
#define L_U8_GPIO_DIR(gpio) ((uint8_t)(1 << ((gpio) + 4)))
/** macro function to set the bit of a gpio pin */
#define L_U8_GPIO_VALUE(gpio) ((uint8_t)(1 << ((gpio) + 6)))
/** Function to set pl2303 gpio pin to output
*
* @param fd_dev opened file descriptor of the USB serial driver
* @param gpio 0 for gp0 pin, 1 for gp1 pin
* @param level 0: low, 1: high
* @return zero in case of success
*
* The function configures the pin specified by gpio param to output mode.
* and sets the pin level according to the level parameter.
*/
int pl2303_gpio_out(int fd_dev, int gpio, int level)
{
int res;
int arg;
/* read current configuration */
res = ioctl(fd_dev, PL2303_GPIO_GET, &arg);
if(res < 0) {
perror("ioctl get");
return -1;
}
/* construct new register value */
arg |= L_U8_GPIO_DIR(gpio);
if(level)
arg |= L_U8_GPIO_VALUE(gpio);
else
arg &= ~L_U8_GPIO_VALUE(gpio);
/* write new value */
res = ioctl(fd_dev, PL2303_GPIO_SET, &arg);
if(res < 0) {
perror("ioctl set");
return -1;
}
return 0;
}
The pl2303 driver patch:
--- a/drivers/usb/serial/pl2303.c 2012-04-02 19:32:52.000000000 +0200
+++ b/drivers/usb/serial/pl2303.c 2012-05-29 20:54:08.000000000 +0200
@@ -36,7 +36,14 @@
*/
#define DRIVER_DESC "Prolific PL2303 USB to serial adaptor driver"
+/* GPIO ioctl magic number */
+#define PL2303_GPIO_MAGIC 'v'
+/* GPIO ioctl NR field */
+#define PL2303_GPIO_NR 0xac
+
static bool debug;
+/* initialize pl2303hx gpio pins to input */
+static int gpio = 0x00;
#define PL2303_CLOSING_WAIT (30*HZ)
@@ -223,6 +230,10 @@
pl2303_vendor_write(2, 0x44, serial);
else
pl2303_vendor_write(2, 0x24, serial);
+ /* initialize GPIO */
+ pl2303_vendor_write(1, gpio, serial);
+ pl2303_vendor_read(0x0081, 0, serial, buf);
+ dbg("GPIO read: 0x%x", buf[0]);
kfree(buf);
return 0;
@@ -621,6 +632,50 @@
return 0;
}
+static int pl2303_gpio_ioctl(struct usb_serial_port* port,
+ unsigned int cmd, unsigned long arg)
+{
+ int value;
+ unsigned char buf[10];
+ struct usb_serial* serial = NULL;
+
+ if(port)
+ serial = port->serial;
+ if(NULL == serial)
+ return -EINVAL;
+
+ /* check if it is a gpio ioctl */
+ if((PL2303_GPIO_MAGIC != _IOC_TYPE(cmd)) ||
+ (PL2303_GPIO_NR != _IOC_NR(cmd)))
+ return -ENOIOCTLCMD;
+
+ /* check argument size */
+ if(sizeof(value) != _IOC_SIZE(cmd))
+ return -EINVAL;
+
+ memset(buf, 0, sizeof(buf));
+
+ switch(_IOC_DIR(cmd)) {
+ case _IOC_READ:
+ /* read GPIO register */
+ if(pl2303_vendor_read(0x0081, 0, serial, buf) < 1)
+ return -EIO;
+ value = buf[0];
+ if(copy_to_user((void __user *)arg, &value, sizeof(value)))
+ return -EFAULT;
+ break;
+ case _IOC_WRITE:
+ if(copy_from_user(&value, (void __user*)arg, sizeof(value)))
+ return -EFAULT;
+ if(pl2303_vendor_write(1, value, serial))
+ return -EIO;
+ break;
+ default:
+ return -EINVAL;
+ }
+ return 0;
+}
+
static int pl2303_ioctl(struct tty_struct *tty,
unsigned int cmd, unsigned long arg)
{
@@ -645,6 +700,9 @@
dbg("%s (%d) TIOCMIWAIT", __func__, port->number);
return wait_modem_info(port, arg);
default:
+ if(PL2303_GPIO_MAGIC == _IOC_TYPE(cmd)) {
+ return pl2303_gpio_ioctl(port, cmd, arg);
+ }
dbg("%s not supported = 0x%04x", __func__, cmd);
break;
}
@@ -884,5 +942,6 @@
MODULE_LICENSE("GPL");
module_param(debug, bool, S_IRUGO | S_IWUSR);
+module_param(gpio, int, S_IRUGO | S_IWUSR);
MODULE_PARM_DESC(debug, "Debug enabled or not");
--
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