linux-kernel - Re: [PATCH v5 2/3] usb: serial: xr

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Message-ID: <X8ZmfbQp7/BGgxec@localhost>
Date:   Tue, 1 Dec 2020 16:51:25 +0100
From:   Johan Hovold <johan@...nel.org>
To:     Linus Walleij <linus.walleij@...aro.org>
Cc:     Manivannan Sadhasivam <mani@...nel.org>,
        Johan Hovold <johan@...nel.org>,
        Greg KH <gregkh@...uxfoundation.org>,
        linux-usb <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        patong.mxl@...il.com,
        Mauro Carvalho Chehab <mchehab+huawei@...nel.org>,
        angelo.dureghello@...esys.com,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>
Subject: Re: [PATCH v5 2/3] usb: serial: xr_serial: Add gpiochip support

On Tue, Dec 01, 2020 at 03:37:38PM +0100, Linus Walleij wrote:
> On Sun, Nov 22, 2020 at 6:08 PM Manivannan Sadhasivam <mani@...nel.org> wrote:
> 
> > Add gpiochip support for Maxlinear/Exar USB to serial converter
> > for controlling the available gpios.

> One minor notice:
> 
> > +enum gpio_pins {
> > +       GPIO_RI = 0,
> > +       GPIO_CD,
> > +       GPIO_DSR,
> > +       GPIO_DTR,
> > +       GPIO_CTS,
> > +       GPIO_RTS,
> > +       GPIO_MAX,
> > +};
> 
> You know the names of the pins...
> 
> > +       port_priv->gc.ngpio = 6;
> > +       port_priv->gc.label = "xr_gpios";
> > +       port_priv->gc.request = xr_gpio_request;
> > +       port_priv->gc.free = xr_gpio_free;
> > +       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;
> 
> So assign port_priv->gc.names here as well with an array
> of strings with the names ("RI", "CD", ... etc).
> This makes it look really nice in userspace if you do
> e.g. "lsgpio".

Last time we tried that gpiolib still used a flat namespace so that you
can't have have more than one device using the same names. Unless that
has changed this is a no-go. See

	https://lore.kernel.org/r/20180930122703.7115-1-johan@kernel.org

for our previous discussion about this.

Johan