On 2020-12-01 15:01, Marc Zyngier wrote:
Hi Linus,
On 2020-12-01 14:10, Linus Walleij wrote:
The FTDI adapters present all potentially available GPIO
lines to userspace, and they are often also visibly
available on things like breakout boards. These are
appetizing targets for random GPIO tinkering such as
bit-banging or other industrial control over USB.
When a user attempts to use one of the GPIO lines, they
can get the opaque error -ENODEV, because the flashed
configuration says that the line is not in GPIO mode
but another alternative function.
We had one user run into this, debug and finally fix the
problem using ftx-prog.
Well, you gave me 2/3 of the solution ;-). How about adding
a pointer to this tool? [1]
Give the user some more helpful dmesg text and a pointer
to ftx-prog when the error occurs.
Reported-by: Marc Zyngier <maz@xxxxxxxxxx>
Signed-off-by: Linus Walleij <linus.walleij@xxxxxxxxxx>
---
drivers/usb/serial/ftdi_sio.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/drivers/usb/serial/ftdi_sio.c
b/drivers/usb/serial/ftdi_sio.c
index e0f4c3d9649c..405fec78f2fc 100644
--- a/drivers/usb/serial/ftdi_sio.c
+++ b/drivers/usb/serial/ftdi_sio.c
@@ -1841,8 +1841,11 @@ static int ftdi_gpio_request(struct gpio_chip
*gc, unsigned int offset)
struct ftdi_private *priv = usb_get_serial_port_data(port);
int result;
- if (priv->gpio_altfunc & BIT(offset))
+ if (priv->gpio_altfunc & BIT(offset)) {
+ dev_err(&port->dev, "FTDI firmware says line is not in GPIO
mode\n");
+ dev_err(&port->dev, "if you really know what you're doing the flash
can be reconfigured using ftx-prog\n");
return -ENODEV;
+ }
mutex_lock(&priv->gpio_lock);
if (!priv->gpio_used) {
It occurs to me that since the driver already knows which of the CBUS
pins are unusable, we should maybe find a way to expose the line as
"reserved", one way or another? Generic tools such as gpioinfo would
(or should?) be able to display the status of the pin to the user.
enum gpio_v2_line_flag doesn't have a "reserved" flag, so maybe
GPIO_V2_LINE_FLAG_USED is an adequate way to mark the line as
being unavailable for userspace?
And to clarify what I mean, here's a patchlet that does the trick.
maz@tiger-roach:~$ sudo gpioinfo gpiochip3
gpiochip3 - 4 lines:
line 0: unnamed unused output active-high
line 1: "AltFunc" kernel input active-high [used]
line 2: "AltFunc" kernel input active-high [used]
line 3: "AltFunc" kernel input active-high [used]
It at least make clear that you can't grab the GPIO. Of course, you
don't get the message that you just added...
Thoughts?
M.
diff --git a/drivers/usb/serial/ftdi_sio.c
b/drivers/usb/serial/ftdi_sio.c
index e0f4c3d9649c..00da3f42139f 100644
--- a/drivers/usb/serial/ftdi_sio.c
+++ b/drivers/usb/serial/ftdi_sio.c
@@ -44,6 +44,8 @@
#include "ftdi_sio.h"
#include "ftdi_sio_ids.h"
+#include "../../gpio/gpiolib.h"
+
#define DRIVER_AUTHOR "Greg Kroah-Hartman <greg@xxxxxxxxx>, Bill Ryder
<bryder@xxxxxxx>, Kuba Ober <kuba@xxxxxxxxxxxxxxx>, Andreas Mohr, Johan
Hovold <jhovold@xxxxxxxxx>"
#define DRIVER_DESC "USB FTDI Serial Converters Driver"
@@ -2143,11 +2145,13 @@ static int ftdi_gpio_init_ftx(struct
usb_serial_port *port)
return result;
}
+static const char *altfunc = "AltFunc";
+
static int ftdi_gpio_init(struct usb_serial_port *port)
{
struct ftdi_private *priv = usb_get_serial_port_data(port);
struct usb_serial *serial = port->serial;
- int result;
+ int result, i;
switch (priv->chip_type) {
case FT232H:
@@ -2183,10 +2187,23 @@ static int ftdi_gpio_init(struct usb_serial_port
*port)
priv->gc.can_sleep = true;
result = gpiochip_add_data(&priv->gc, port);
- if (!result)
- priv->gpio_registered = true;
+ if (result)
+ return result;
- return result;
+ priv->gpio_registered = true;
+
+ for (i = 0; i < priv->gc.ngpio; i++) {
+ struct gpio_desc *desc;
+
+ if (!(priv->gpio_altfunc & BIT(i)))
+ continue;
+
+ desc = gpiochip_get_desc(&priv->gc, i);
+ desc->flags |= BIT(FLAG_REQUESTED);
+ desc->name = altfunc;
+ }
+
+ return 0;
}
static void ftdi_gpio_remove(struct usb_serial_port *port)
--
Jazz is not dead. It just smells funny...
