staging: gpib: change return type of t1_delay function to report errors

The current code returns "unsigned int" and it doesn't handle errors
correctly if it happens during ioctl call for t1 delay configuration.

The ni_usb_t1_delay(), from NI, is the only function returning -1
at this point. The caller, t1_delay_ioctl(), doesn't check for errors
and sets board->t1_nano_sec to -1 and returns success.
The board->t1_nano_sec value is also used in ni_usb_setup_t1_delay()
besides the ioctl call and a value of -1 is treated as being above 1100ns.
It may or may not have a noticeable effect, but it's obviously not right
considering the content of ni_usb_setup_t1_delay().

Typical delays are in the 200-2000 range, but definitely not more
than INT_MAX so we can fix this code by changing the return type to int
and adding a check for errors. While we're at it, lets change the error
code in ni_usb_t1_delay() from -1 and instead propagate the error from
ni_usb_write_registers().

Fixes: 4e127de ("staging: gpib: Add National Instruments USB GPIB driver")
Signed-off-by: Rodrigo Gobbi <rodrigo.gobbi.7@gmail.com>
Link: https://lore.kernel.org/r/20250225014811.77995-1-rodrigo.gobbi.7@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: losgobbi

drivers/staging/gpib/agilent_82350b/agilent_82350b.c

@@ -455,8 +455,7 @@ static int agilent_82350b_line_status(const struct gpib_board *board)
 	return tms9914_line_status(board, &priv->tms9914_priv);
 }
 
-static unsigned int agilent_82350b_t1_delay(struct gpib_board *board,
-					    unsigned int nanosec)
+static int agilent_82350b_t1_delay(struct gpib_board *board, unsigned int nanosec)
 {
 	struct agilent_82350b_priv *a_priv = board->private_data;
 	static const int nanosec_per_clock = 30;

drivers/staging/gpib/agilent_82357a/agilent_82357a.c

@@ -1071,7 +1071,7 @@ static unsigned short nanosec_to_fast_talker_bits(unsigned int *nanosec)
 	return bits;
 }
 
-static unsigned int agilent_82357a_t1_delay(struct gpib_board *board, unsigned int nanosec)
+static int agilent_82357a_t1_delay(struct gpib_board *board, unsigned int nanosec)
 {
 	struct agilent_82357a_priv *a_priv = board->private_data;
 	struct usb_device *usb_dev;

drivers/staging/gpib/cb7210/cb7210.c

@@ -408,7 +408,7 @@ static int cb7210_line_status(const struct gpib_board *board)
 	return status;
 }
 
-static unsigned int cb7210_t1_delay(struct gpib_board *board, unsigned int nano_sec)
+static int cb7210_t1_delay(struct gpib_board *board, unsigned int nano_sec)
 {
 	struct cb7210_priv *cb_priv = board->private_data;
 	struct nec7210_priv *nec_priv = &cb_priv->nec7210_priv;

drivers/staging/gpib/cec/cec_gpib.c

@@ -174,7 +174,7 @@ static uint8_t cec_serial_poll_status(struct gpib_board *board)
 	return nec7210_serial_poll_status(board, &priv->nec7210_priv);
 }
 
-static unsigned int cec_t1_delay(struct gpib_board *board, unsigned int nano_sec)
+static int cec_t1_delay(struct gpib_board *board, unsigned int nano_sec)
 {
 	struct cec_priv *priv = board->private_data;
 

drivers/staging/gpib/common/gpib_os.c

@@ -1990,8 +1990,11 @@ static int t1_delay_ioctl(struct gpib_board *board, unsigned long arg)
 
 	delay = cmd;
 
-	board->t1_nano_sec = board->interface->t1_delay(board, delay);
+	retval = board->interface->t1_delay(board, delay);
+	if (retval < 0)
+		return retval;
 
+	board->t1_nano_sec = retval;
 	return 0;
 }
 

drivers/staging/gpib/eastwood/fluke_gpib.c

@@ -224,7 +224,7 @@ static int fluke_line_status(const struct gpib_board *board)
 	return status;
 }
 
-static unsigned int fluke_t1_delay(struct gpib_board *board, unsigned int nano_sec)
+static int fluke_t1_delay(struct gpib_board *board, unsigned int nano_sec)
 {
 	struct fluke_priv *e_priv = board->private_data;
 	struct nec7210_priv *nec_priv = &e_priv->nec7210_priv;

drivers/staging/gpib/fmh_gpib/fmh_gpib.c

@@ -261,7 +261,7 @@ static int fmh_gpib_line_status(const struct gpib_board *board)
 	return status;
 }
 
-static unsigned int fmh_gpib_t1_delay(struct gpib_board *board, unsigned int nano_sec)
+static int fmh_gpib_t1_delay(struct gpib_board *board, unsigned int nano_sec)
 {
 	struct fmh_priv *e_priv = board->private_data;
 	struct nec7210_priv *nec_priv = &e_priv->nec7210_priv;

drivers/staging/gpib/gpio/gpib_bitbang.c

@@ -1009,7 +1009,7 @@ static uint8_t bb_serial_poll_status(struct gpib_board *board)
 	return 0; // -ENOENT;
 }
 
-static unsigned int bb_t1_delay(struct gpib_board *board,  unsigned int nano_sec)
+static int bb_t1_delay(struct gpib_board *board,  unsigned int nano_sec)
 {
 	struct bb_priv *priv = board->private_data;
 

drivers/staging/gpib/hp_82335/hp82335.c

@@ -165,7 +165,7 @@ static int hp82335_line_status(const struct gpib_board *board)
 	return tms9914_line_status(board, &priv->tms9914_priv);
 }
 
-static unsigned int hp82335_t1_delay(struct gpib_board *board, unsigned int nano_sec)
+static int hp82335_t1_delay(struct gpib_board *board, unsigned int nano_sec)
 {
 	struct hp82335_priv *priv = board->private_data;
 

drivers/staging/gpib/hp_82341/hp_82341.c

@@ -396,7 +396,7 @@ static int hp_82341_line_status(const struct gpib_board *board)
 	return tms9914_line_status(board, &priv->tms9914_priv);
 }
 
-static unsigned int hp_82341_t1_delay(struct gpib_board *board, unsigned int nano_sec)
+static int hp_82341_t1_delay(struct gpib_board *board, unsigned int nano_sec)
 {
 	struct hp_82341_priv *priv = board->private_data;