linux-kernel - Re: [PATCH v6] USB: serial: ftdi_sio: implement GPIO support for FT-X devices

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Message-ID: <20180925101523.GD3332@localhost>
Date:   Tue, 25 Sep 2018 12:15:23 +0200
From:   Johan Hovold <johan@...nel.org>
To:     Karoly Pados <pados@...os.hu>
Cc:     Johan Hovold <johan@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        Loic Poulain <loic.poulain@...aro.org>
Subject: Re: [PATCH v6] USB: serial: ftdi_sio: implement GPIO support for
 FT-X devices

On Tue, Sep 25, 2018 at 12:06:35PM +0200, Johan Hovold wrote:
> On Mon, Sep 24, 2018 at 04:31:51PM +0200, Karoly Pados wrote:

> > +static void ftdi_gpio_set_multiple(struct gpio_chip *gc,
> > +				   unsigned long *mask, unsigned long *bits)
> > +{
> > +	struct usb_serial_port *port = gpiochip_get_data(gc);
> > +	struct ftdi_private *priv = usb_get_serial_port_data(port);
> > +
> > +	mutex_lock(&priv->gpio_lock);
> > +
> > +	priv->gpio_value &= ~(*mask);
> > +	priv->gpio_value |= *bits;
> 
> gpiolib doesn't clear bits not in mask for you, so you need to OR with
> *mask here to avoid setting random other bits.

That was of course meant to be: *AND* with *mask.

Johan