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: 4e127de14fa7 ("staging: gpib: Add National Instruments USB GPIB driver")
Signed-off-by: Rodrigo Gobbi <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/staging/gpib/agilent_82350b/agilent_82350b.c

···
 	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

···
 	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

···
 	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

···
 	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

···
 
 	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

···
 	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

···
 	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

···
 	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

···
 	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

···
 	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;
 

drivers/staging/gpib/include/gpib_types.h

···
 	 */
 	uint8_t (*serial_poll_status)(struct gpib_board *board);
 	/* adjust T1 delay */
-	unsigned int (*t1_delay)(struct gpib_board *board, unsigned int nano_sec);
+	int (*t1_delay)(struct gpib_board *board, unsigned int nano_sec);
 	/* go to local mode */
 	void (*return_to_local)(struct gpib_board *board);
 	/* board does not support 7 bit eos comparisons */

drivers/staging/gpib/include/nec7210.h

···
 				    struct nec7210_priv *priv, int ist);
 uint8_t nec7210_serial_poll_status(struct gpib_board *board,
 				   struct nec7210_priv *priv);
-unsigned int nec7210_t1_delay(struct gpib_board *board,
-			      struct nec7210_priv *priv, unsigned int nano_sec);
+int nec7210_t1_delay(struct gpib_board *board,
+		     struct nec7210_priv *priv, unsigned int nano_sec);
 void nec7210_return_to_local(const struct gpib_board *board, struct nec7210_priv *priv);
 
 // utility functions

drivers/staging/gpib/ines/ines.h

···
 void ines_serial_poll_response(struct gpib_board *board, uint8_t status);
 uint8_t ines_serial_poll_status(struct gpib_board *board);
 int ines_line_status(const struct gpib_board *board);
-unsigned int ines_t1_delay(struct gpib_board *board, unsigned int nano_sec);
+int ines_t1_delay(struct gpib_board *board, unsigned int nano_sec);
 void ines_return_to_local(struct gpib_board *board);
 
 // interrupt service routines

drivers/staging/gpib/ines/ines_gpib.c

···
 	ines_outb(priv, count & 0xff, XFER_COUNT_LOWER);
 }
 
-unsigned int ines_t1_delay(struct gpib_board *board, unsigned int nano_sec)
+int ines_t1_delay(struct gpib_board *board, unsigned int nano_sec)
 {
 	struct ines_priv *ines_priv = board->private_data;
 	struct nec7210_priv *nec_priv = &ines_priv->nec7210_priv;

drivers/staging/gpib/lpvo_usb_gpib/lpvo_usb_gpib.c

···
 
 /* t1_delay */
 
-static unsigned int usb_gpib_t1_delay(struct gpib_board *board, unsigned int nano_sec)
+static int usb_gpib_t1_delay(struct gpib_board *board, unsigned int nano_sec)
 {
 	return 0;
 }

drivers/staging/gpib/nec7210/nec7210.c

···
 }
 EXPORT_SYMBOL(nec7210_release_rfd_holdoff);
 
-unsigned int nec7210_t1_delay(struct gpib_board *board, struct nec7210_priv *priv,
-			      unsigned int nano_sec)
+int nec7210_t1_delay(struct gpib_board *board, struct nec7210_priv *priv,
+		     unsigned int nano_sec)
 {
 	unsigned int retval;
 

drivers/staging/gpib/ni_usb/ni_usb_gpib.c

···
 	return i;
 }
 
-static unsigned int ni_usb_t1_delay(struct gpib_board *board, unsigned int nano_sec)
+static int ni_usb_t1_delay(struct gpib_board *board, unsigned int nano_sec)
 {
 	int retval;
 	struct ni_usb_priv *ni_priv = board->private_data;
···
 	retval = ni_usb_write_registers(ni_priv, writes, i, &ibsta);
 	if (retval < 0) {
 		dev_err(&usb_dev->dev, "register write failed, retval=%i\n", retval);
-		return -1;	//FIXME should change return type to int for error reporting
+		return retval;
 	}
 	board->t1_nano_sec = actual_ns;
 	ni_usb_soft_update_status(board, ibsta, 0);

drivers/staging/gpib/pc2/pc2_gpib.c

···
 	return nec7210_serial_poll_status(board, &priv->nec7210_priv);
 }
 
-static unsigned int pc2_t1_delay(struct gpib_board *board, unsigned int nano_sec)
+static int pc2_t1_delay(struct gpib_board *board, unsigned int nano_sec)
 {
 	struct pc2_priv *priv = board->private_data;
 

drivers/staging/gpib/tnt4882/tnt4882_gpib.c

···
 	return status;
 }
 
-static unsigned int tnt4882_t1_delay(struct gpib_board *board, unsigned int nano_sec)
+static int tnt4882_t1_delay(struct gpib_board *board, unsigned int nano_sec)
 {
 	struct tnt4882_priv *tnt_priv = board->private_data;
 	struct nec7210_priv *nec_priv = &tnt_priv->nec7210_priv;