Re: [PATCH] USB: serial: pl2303: add PL2303G GPIO_A and GPIO_B functions

[Johan Hovold <johan@kernel.org>]

On Wed, Jun 18, 2025 at 08:35:13PM +0800, Charles Yeh wrote:
> PL2303G (TYPE_HXN) series ICs: PL2303GC, PL2303GS, PL2303GT, PL2303GR,.. etc.
> 
> For example:
> PL2303GC can provide up to 16 GPIO (general purpose input/output) signals.
> they are composed of GPIO_A0~A7 and GPIO_B0~B7 respectively.
> 
> In addition to the original UART functions such as Tx, Rx, RTS, CTS, etc.,
> users can also use GPIO to implement certain applications,
> such as turning on/off the LED power.
> 
> Users can download the PL2303G Linux GPIO app: PL2303G_Linux_GPIO_Test.c
> from the Prolific website.
> 
> Signed-off-by: Charles Yeh <charlesyeh522@gmail.com>
> ---
>  drivers/usb/serial/pl2303.c | 182 ++++++++++++++++++++++++++++++++++++
>  1 file changed, 182 insertions(+)
> 
> diff --git a/drivers/usb/serial/pl2303.c b/drivers/usb/serial/pl2303.c
> index 22579d0d8ab8..be7e695bea60 100644
> --- a/drivers/usb/serial/pl2303.c
> +++ b/drivers/usb/serial/pl2303.c
> @@ -175,6 +175,37 @@ MODULE_DEVICE_TABLE(usb, id_table);
>  #define PL2303_HXN_FLOWCTRL_RTS_CTS	0x18
>  #define PL2303_HXN_FLOWCTRL_XON_XOFF	0x0c
>  
> +
> +struct PL2303G_GPIO {
> +	u8 GP_Branch;
> +	u8 Number;
> +	u8 Value;

We use lower case symbol names in the kernel.

> +};
> +
> +
> +#define GPIO_AB_CONTROL_MODE		_IOW(0x81, 10, struct PL2303G_GPIO)
> +#define GPIO_AB_OUTPUT_MODE		_IOW(0x81, 11, struct PL2303G_GPIO)
> +#define GPIO_AB_SET_VALUE		_IOW(0x81, 12, struct PL2303G_GPIO)
> +#define GPIO_AB_GET_VALUE		_IOR(0x81, 13, struct PL2303G_GPIO)

No, custom ioctls won't do. We have a standard interface for accessing
GPIOs so you need to model this as gpio chips similar to what the
ftdi_sio and cp210x drivers do.

> +static int pl2303_ioctl(struct tty_struct *tty,
> +			unsigned int cmd, unsigned long arg)
> +{
> +	int retval = 0;
> +	struct serial_struct ser;
> +	struct usb_serial_port *port = tty->driver_data;
> +	struct usb_serial *serial = port->serial;
> +
> +	switch (cmd) {
> +	case TIOCGSERIAL:
> +		memset(&ser, 0, sizeof(ser));
> +		ser.type = PORT_16654;
> +		ser.line = port->minor;
> +		ser.port = port->port_number;
> +		ser.baud_base = 460800;
> +
> +		if (copy_to_user((void __user *)arg, &ser, sizeof(ser)))
> +			return -EFAULT;
> +
> +		return 0;

This looks unrelated.

> +	case GPIO_AB_CONTROL_MODE:
> +		retval = pl2303N_gpio_set(serial, (void __user *) arg,
> +								PL2303N_CE_MODE);
> +		break;
> +	case GPIO_AB_OUTPUT_MODE:
> +		retval = pl2303N_gpio_set(serial, (void __user *) arg,
> +								PL2303N_OE_MODE);
> +		break;
> +	case GPIO_AB_SET_VALUE:
> +		retval = pl2303N_gpio_set(serial, (void __user *) arg,
> +								PL2303N_SET_MODE);
> +		break;
> +	case GPIO_AB_GET_VALUE:
> +		retval = pl2303N_gpio_get(serial, (void __user *) arg,
> +								PL2303N_GET_MODE);
> +		break;
> +	default:
> +		retval = -ENOIOCTLCMD;
> +		break;
> +	}
> +
> +	return retval;
> +
> +}

Johan