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

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Date:   Tue, 25 Sep 2018 10:46:30 +0000
From:   "Karoly Pados" <pados@...os.hu>
To:     "Johan Hovold" <johan@...nel.org>
Cc:     "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

Hi,

>> +#if defined(CONFIG_GPIOLIB)
>> +static const char * const ftdi_ftx_gpio_names[] = {
>> + "CBUS0", "CBUS1", "CBUS2", "CBUS3"
>> +};
>> +#endif
> 
> We want to keep the ifdeffery to a minimum, so move this inside the
> gpiolib ifdef below (and possibly even into the function where it is
> used).
> 
> Also note that these names are shared with FT232R, but not with FT232H.
> 

What naming do you suggest then?

My personal preference would be however to leave this name as is, because
this patch only adds support for the FT-X. Even if support for others can 
be added relatively trivially after this, there is explicitly no GPIO 
support for FT232R *yet*. If somebody else adds GPIO support for the FT232R
in a later patch, he/she should make corresponding adjustments themselves,
including naming changes. IMHO.

>> +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.

I guess you meant AND here?

>> + if (priv->gpio_output & BIT(gpio))
>> + return 0;
>> + else
>> + return 1;
> 
> This could just simplified using negation (!), but perhaps this is
> easier to parse as it stands.
> 

Sorry, it is not clear what your preferred action here is. 
So should I leave it as is then or not?

Karoly