Re: [PATCH] USB: serial: cp210x: fix CP2105 GPIO registration

[Maarten Brock <m.brock@vanmierlo.com>]

On 2021-11-26 10:43, Johan Hovold wrote:
> When generalising GPIO support and adding support for CP2102N, the GPIO
> registration for some CP2105 devices accidentally broke. Specifically,
> when all the pins of a port are in "modem" mode, and thus unavailable
> for GPIO use, the GPIO chip would now be registered without having
> initialised the number of GPIO lines. This would in turn be rejected by
> gpiolib and some errors messages would be printed (but importantly 
> probe
> would still succeed).
> 
> Fix this by initialising the number of GPIO lines before registering 
> the
> GPIO chip.
> 
> Note that as for the other device types, and as when all CP2105 pins 
> are
> muxed for LED function, the GPIO chip is registered also when no pins
> are available for GPIO use.
> 
> Reported-by: Maarten Brock <m.brock@vanmierlo.com>
> Link: 
> https://lore.kernel.org/r/5eb560c81d2ea1a2b4602a92d9f48a89@vanmierlo.com
> Fixes: c8acfe0aadbe ("USB: serial: cp210x: implement GPIO support for 
> CP2102N")
> Cc: stable@vger.kernel.org      # 4.19
> Cc: Karoly Pados <pados@pados.hu>
> Signed-off-by: Johan Hovold <johan@kernel.org>
> ---
>  drivers/usb/serial/cp210x.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/usb/serial/cp210x.c b/drivers/usb/serial/cp210x.c
> index 7705328034ca..8a60c0d56863 100644
> --- a/drivers/usb/serial/cp210x.c
> +++ b/drivers/usb/serial/cp210x.c
> @@ -1635,6 +1635,8 @@ static int cp2105_gpioconf_init(struct usb_serial 
> *serial)
> 
>  	/*  2 banks of GPIO - One for the pins taken from each serial port */
>  	if (intf_num == 0) {
> +		priv->gc.ngpio = 2;
> +
>  		if (mode.eci == CP210X_PIN_MODE_MODEM) {
>  			/* mark all GPIOs of this interface as reserved */
>  			priv->gpio_altfunc = 0xff;
> @@ -1645,8 +1647,9 @@ static int cp2105_gpioconf_init(struct usb_serial 
> *serial)
>  		priv->gpio_pushpull = (u8)((le16_to_cpu(config.gpio_mode) &
>  						CP210X_ECI_GPIO_MODE_MASK) >>
>  						CP210X_ECI_GPIO_MODE_OFFSET);
> -		priv->gc.ngpio = 2;
>  	} else if (intf_num == 1) {
> +		priv->gc.ngpio = 3;
> +
>  		if (mode.sci == CP210X_PIN_MODE_MODEM) {
>  			/* mark all GPIOs of this interface as reserved */
>  			priv->gpio_altfunc = 0xff;
> @@ -1657,7 +1660,6 @@ static int cp2105_gpioconf_init(struct usb_serial 
> *serial)
>  		priv->gpio_pushpull = (u8)((le16_to_cpu(config.gpio_mode) &
>  						CP210X_SCI_GPIO_MODE_MASK) >>
>  						CP210X_SCI_GPIO_MODE_OFFSET);
> -		priv->gc.ngpio = 3;
>  	} else {
>  		return -ENODEV;
>  	}

Tested-by: Maarten Brock <m.brock@vanmierlo.com>