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

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Message-ID: <20180925120825.GF3332@localhost>
Date:   Tue, 25 Sep 2018 14:08:25 +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 11:11:03AM +0000, Karoly Pados wrote:
> >> + 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?
> > 
> > Just do
> > 
> > res = !(priv->gpio_output & BIT(gpio));
> > 
> 
> Locking here? priv->gpio_output is a u8, there is no way it can be partially
> written. Or am I missing something else?

No, you're right, no locking is needed.

Johan