[PATCH 3/4] USB: serial: ftdi_sio: Log the CBUS GPIO validity

[Marc Zyngier <maz@kernel.org>]

The validity of the ftdi CBUS GPIO is pretty hidden so far,
and finding out *why* some GPIOs don't work is sometimes
hard to identify. So let's help the user by displaying the
map of the CBUS pins that are valid for a GPIO.

Also, tell the user about the magic ftx-prog tool that can
make GPIOs appear: https://github.com/richardeoin/ftx-prog

Suggested-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>
---
 drivers/usb/serial/ftdi_sio.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/usb/serial/ftdi_sio.c b/drivers/usb/serial/ftdi_sio.c
index 13e575f16bcd..b9d3b33891fc 100644
--- a/drivers/usb/serial/ftdi_sio.c
+++ b/drivers/usb/serial/ftdi_sio.c
@@ -2012,6 +2012,15 @@ static int ftdi_gpio_init_valid_mask(struct gpio_chip *gc,
 
 	bitmap_complement(valid_mask, &map, ngpios);
 
+	if (bitmap_empty(valid_mask, ngpios))
+		dev_warn(&port->dev, "No usable GPIO\n");
+	else
+		dev_info(&port->dev, "Enabling CBUS%*pbl for GPIO\n",
+			 ngpios, valid_mask);
+
+	if (!bitmap_full(valid_mask, ngpios))
+		dev_warn_once(&port->dev, "Consider using a tool such as ftx-prog to enable GPIOs if required\n");
+
 	return 0;
 }
 
-- 
2.28.0