linux-kernel - Re: [PATCH 2/2] usb: serial: xr

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Date:   Wed, 29 Apr 2020 19:59:45 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Manivannan Sadhasivam <mani@...nel.org>
Cc:     johan@...nel.org, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org, patong.mxl@...il.com,
        Linus Walleij <linus.walleij@...aro.org>,
        linux-gpio@...r.kernel.org
Subject: Re: [PATCH 2/2] usb: serial: xr_serial: Add gpiochip support

On Wed, Apr 29, 2020 at 11:17:27PM +0530, Manivannan Sadhasivam wrote:
> Hi Greg,
> 
> On Wed, Apr 29, 2020 at 01:26:51AM +0530, mani@...nel.org wrote:
> > From: Manivannan Sadhasivam <mani@...nel.org>
> > 
> > Add gpiochip support for Maxlinear/Exar USB to serial converter
> > for controlling the available gpios.
> > 
> > Cc: Linus Walleij <linus.walleij@...aro.org>
> > Cc: linux-gpio@...r.kernel.org
> > Signed-off-by: Manivannan Sadhasivam <mani@...nel.org>
> > ---
> >  drivers/usb/serial/xr_serial.c | 186 ++++++++++++++++++++++++++++++++-
> >  drivers/usb/serial/xr_serial.h |   7 ++
> >  2 files changed, 192 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/usb/serial/xr_serial.c b/drivers/usb/serial/xr_serial.c
> > index ea4a0b167d3f..d86fd40839f8 100644
> > --- a/drivers/usb/serial/xr_serial.c
> > +++ b/drivers/usb/serial/xr_serial.c
> > @@ -476,6 +476,189 @@ static void xr_break_ctl(struct tty_struct *tty, int break_state)
> >  		   state);
> >  }
> >  
> > +#ifdef CONFIG_GPIOLIB
> > +
> 
> [...]
> 
> > +
> > +static int xr_gpio_init(struct usb_serial_port *port)
> > +{
> > +	struct xr_port_private *port_priv = usb_get_serial_port_data(port);
> > +	int ret = 0;
> > +
> > +	if (port_priv->idProduct == XR21V141X_ID)
> > +		ret = xr21v141x_gpio_init(port);
> > +
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	port_priv->gc.label = "xr_gpios";
> > +	port_priv->gc.request = xr_gpio_request;
> > +	port_priv->gc.get_direction = xr_gpio_direction_get;
> > +	port_priv->gc.direction_input = xr_gpio_direction_input;
> > +	port_priv->gc.direction_output = xr_gpio_direction_output;
> > +	port_priv->gc.get = xr_gpio_get;
> > +	port_priv->gc.set = xr_gpio_set;
> > +	port_priv->gc.owner = THIS_MODULE;
> > +	port_priv->gc.parent = &port->dev;
> > +	port_priv->gc.base = -1;
> > +	port_priv->gc.can_sleep = true;
> > +
> > +	ret = gpiochip_add_data(&port_priv->gc, port);
> > +	if (!ret)
> > +		port_priv->gpio_registered = true;
> > +
> > +	return ret;
> > +}
> > +
> > +static void xr_gpio_remove(struct usb_serial_port *port)
> > +{
> > +	struct xr_port_private *port_priv = usb_get_serial_port_data(port);
> > +
> > +	if (port_priv->gpio_registered) {
> > +		gpiochip_remove(&port_priv->gc);
> > +		port_priv->gpio_registered = false;
> > +	}
> > +}
> > +
> > +#else
> > +
> > +static int xr_gpio_init(struct usb_serial_port *port)
> > +{
> > +	return 0;
> > +}
> > +
> > +static void xr_gpio_remove(struct usb_serial_port *port)
> > +{
> > +	/* Nothing to do */
> > +}
> > +
> > +#endif
> > +
> >  static int xr_port_probe(struct usb_serial_port *port)
> >  {
> >  	struct usb_serial *serial = port->serial;
> > @@ -495,13 +678,14 @@ static int xr_port_probe(struct usb_serial_port *port)
> >  
> >  	usb_set_serial_port_data(port, port_priv);
> >  
> > -	return 0;
> > +	return xr_gpio_init(port);
> 
> Just realised that the gpiochip is registered for 2 interfaces exposed by
> this chip. This is due to the fact that this chip presents CDC-ACM model,
> so there are 2 interfaces (interrupt and bulk IN/OUT).
> 
> We shouldn't need gpiochip for interface 0. So what is the recommended way
> to filter that?

Not create the gpiochip for interface 0?  :)

I really don't know what else to say here, sorry.

greg k-h