staging: gpib: Add return value to request_control

A number of drivers are unable to release control due to hardware or
software limitations. As request_system_control was defined as void,
no error could be signalled.

This patch changes the prototype of request_system_control to int and
adds the appropriate checking and returns. In the case that a board
cannot release control EINVAL is returned. If a driver does not
implement request_system_control EPERM is returned.

Signed-off-by: Dave Penkler <[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_go_to_standby(board, &priv->tms9914_priv);
 }
 
-static void agilent_82350b_request_system_control(struct gpib_board *board,
-						  int request_control)
-
+static int agilent_82350b_request_system_control(struct gpib_board *board, int request_control)
 {
 	struct agilent_82350b_priv *a_priv = board->private_data;
 
···
 			writeb(0, a_priv->gpib_base + INTERNAL_CONFIG_REG);
 	}
 	writeb(a_priv->card_mode_bits, a_priv->gpib_base + CARD_MODE_REG);
-	tms9914_request_system_control(board, &a_priv->tms9914_priv, request_control);
+	return tms9914_request_system_control(board, &a_priv->tms9914_priv, request_control);
 }
 
 static void agilent_82350b_interface_clear(struct gpib_board *board, int assert)

drivers/staging/gpib/agilent_82357a/agilent_82357a.c

···
 	return 0;
 }
 
-//FIXME should change prototype to return int
-static void agilent_82357a_request_system_control(struct gpib_board *board,
-						  int request_control)
+static int agilent_82357a_request_system_control(struct gpib_board *board, int request_control)
 {
 	struct agilent_82357a_priv *a_priv = board->private_data;
 	struct usb_device *usb_dev;
···
 	int i = 0;
 
 	if (!a_priv->bus_interface)
-		return; // -ENODEV;
+		return -ENODEV;
 
 	usb_dev = interface_to_usbdev(a_priv->bus_interface);
 	/* 82357B needs bit to be set in 9914 AUXCR register */
···
 		writes[i].value = AUX_RQC;
 		a_priv->hw_control_bits |= SYSTEM_CONTROLLER;
 	} else {
-		writes[i].value = AUX_RLC;
-		a_priv->is_cic = 0;
-		a_priv->hw_control_bits &= ~SYSTEM_CONTROLLER;
+		return -EINVAL;
 	}
 	++i;
 	writes[i].address = HW_CONTROL;
···
 	retval = agilent_82357a_write_registers(a_priv, writes, i);
 	if (retval)
 		dev_err(&usb_dev->dev, "write_registers() returned error\n");
-	return;// retval;
+	return retval;
 }
 
 static void agilent_82357a_interface_clear(struct gpib_board *board, int assert)
···
 {
 	struct usb_device *usb_dev = interface_to_usbdev(interface);
 	struct gpib_board *board;
-	int i, retval;
+	int i, retval = 0;
 
 	mutex_lock(&agilent_82357a_hotplug_lock);
 
···
 				break;
 		}
 	}
-	if (i == MAX_NUM_82357A_INTERFACES)
+	if (i == MAX_NUM_82357A_INTERFACES) {
+		retval = -ENOENT;
 		goto resume_exit;
+	}
 
 	struct agilent_82357a_priv *a_priv = board->private_data;
 
···
 			return retval;
 		}
 		// set/unset system controller
-		agilent_82357a_request_system_control(board, board->master);
+		retval = agilent_82357a_request_system_control(board, board->master);
 		// toggle ifc if master
 		if (board->master) {
 			agilent_82357a_interface_clear(board, 1);
···
 resume_exit:
 	mutex_unlock(&agilent_82357a_hotplug_lock);
 
-	return 0;
+	return retval;
 }
 
 static struct usb_driver agilent_82357a_bus_driver = {

drivers/staging/gpib/cb7210/cb7210.c

···
 	return nec7210_go_to_standby(board, &priv->nec7210_priv);
 }
 
-static void cb7210_request_system_control(struct gpib_board *board, int request_control)
+static int cb7210_request_system_control(struct gpib_board *board, int request_control)
 {
 	struct cb7210_priv *priv = board->private_data;
 	struct nec7210_priv *nec_priv = &priv->nec7210_priv;
···
 		priv->hs_mode_bits &= ~HS_SYS_CONTROL;
 
 	cb7210_write_byte(priv, priv->hs_mode_bits, HS_MODE);
-	nec7210_request_system_control(board, nec_priv, request_control);
+	return nec7210_request_system_control(board, nec_priv, request_control);
 }
 
 static void cb7210_interface_clear(struct gpib_board *board, int assert)

drivers/staging/gpib/cec/cec_gpib.c

···
 	return nec7210_go_to_standby(board, &priv->nec7210_priv);
 }
 
-static void cec_request_system_control(struct gpib_board *board, int request_control)
+static int cec_request_system_control(struct gpib_board *board, int request_control)
 {
 	struct cec_priv *priv = board->private_data;
 
-	nec7210_request_system_control(board, &priv->nec7210_priv, request_control);
+	return nec7210_request_system_control(board, &priv->nec7210_priv, request_control);
 }
 
 static void cec_interface_clear(struct gpib_board *board, int assert)

drivers/staging/gpib/common/gpib_os.c

···
 	if (retval)
 		return -EFAULT;
 
-	ibrsc(board, request_control);
-
-	return 0;
+	return ibrsc(board, request_control);
 }
 
 static int t1_delay_ioctl(struct gpib_board *board, unsigned long arg)

drivers/staging/gpib/common/iblib.c

···
 	return 0;
 }
 
-	/* FIXME make int */
-void ibrsc(struct gpib_board *board, int request_control)
+int ibrsc(struct gpib_board *board, int request_control)
 {
+	int retval;
+
+	if (!board->interface->request_system_control)
+		return -EPERM;
+
+	retval = board->interface->request_system_control(board, request_control);
+
+	if (retval)
+		return retval;
+
 	board->master = request_control != 0;
-	if (board->interface->request_system_control)
-		board->interface->request_system_control(board, request_control);
+
+	return  0;
 }
 
 /*

drivers/staging/gpib/eastwood/fluke_gpib.c

···
 	return nec7210_go_to_standby(board, &priv->nec7210_priv);
 }
 
-static void fluke_request_system_control(struct gpib_board *board, int request_control)
+static int fluke_request_system_control(struct gpib_board *board, int request_control)
 {
 	struct fluke_priv *priv = board->private_data;
 	struct nec7210_priv *nec_priv = &priv->nec7210_priv;
 
-	nec7210_request_system_control(board, nec_priv, request_control);
+	return nec7210_request_system_control(board, nec_priv, request_control);
 }
 
 static void fluke_interface_clear(struct gpib_board *board, int assert)

drivers/staging/gpib/fmh_gpib/fmh_gpib.c

···
 	return nec7210_go_to_standby(board, &priv->nec7210_priv);
 }
 
-static void fmh_gpib_request_system_control(struct gpib_board *board, int request_control)
+static int fmh_gpib_request_system_control(struct gpib_board *board, int request_control)
 {
 	struct fmh_priv *priv = board->private_data;
 	struct nec7210_priv *nec_priv = &priv->nec7210_priv;
 
-	nec7210_request_system_control(board, nec_priv, request_control);
+	return nec7210_request_system_control(board, nec_priv, request_control);
 }
 
 static void fmh_gpib_interface_clear(struct gpib_board *board, int assert)

drivers/staging/gpib/gpio/gpib_bitbang.c

···
 	return 0;
 }
 
-static void bb_request_system_control(struct gpib_board *board, int request_control)
+static int bb_request_system_control(struct gpib_board *board, int request_control)
 {
 	dbg_printk(2, "%d\n", request_control);
-	if (request_control) {
-		set_bit(CIC_NUM, &board->status);
-		// drive DAV & EOI false, enable NRFD & NDAC irqs
-		SET_DIR_WRITE(board->private_data);
-	} else {
-		clear_bit(CIC_NUM, &board->status);
-	}
+	if (!request_control)
+		return -EINVAL;
+
+	set_bit(CIC_NUM, &board->status);
+	// drive DAV & EOI false, enable NRFD & NDAC irqs
+	SET_DIR_WRITE(board->private_data);
+	return 0;
 }
 
 static void bb_interface_clear(struct gpib_board *board, int assert)

drivers/staging/gpib/hp_82335/hp82335.c

···
 	return tms9914_go_to_standby(board, &priv->tms9914_priv);
 }
 
-static void hp82335_request_system_control(struct gpib_board *board, int request_control)
+static int hp82335_request_system_control(struct gpib_board *board, int request_control)
 {
 	struct hp82335_priv *priv = board->private_data;
 
-	tms9914_request_system_control(board, &priv->tms9914_priv, request_control);
+	return tms9914_request_system_control(board, &priv->tms9914_priv, request_control);
 }
 
 static void hp82335_interface_clear(struct gpib_board *board, int assert)

drivers/staging/gpib/hp_82341/hp_82341.c

···
 	return tms9914_go_to_standby(board, &priv->tms9914_priv);
 }
 
-static void hp_82341_request_system_control(struct gpib_board *board, int request_control)
+static int hp_82341_request_system_control(struct gpib_board *board, int request_control)
 {
 	struct hp_82341_priv *priv = board->private_data;
 
···
 	else
 		priv->mode_control_bits &= ~SYSTEM_CONTROLLER_BIT;
 	outb(priv->mode_control_bits, priv->iobase[0] + MODE_CONTROL_STATUS_REG);
-	tms9914_request_system_control(board, &priv->tms9914_priv, request_control);
+	return tms9914_request_system_control(board, &priv->tms9914_priv, request_control);
 }
 
 static void hp_82341_interface_clear(struct gpib_board *board, int assert)

drivers/staging/gpib/include/gpib_proto.h

···
 int ibrd(struct gpib_board *board, u8 *buf, size_t length, int *end_flag, size_t *bytes_read);
 int ibrpp(struct gpib_board *board, u8 *buf);
 int ibrsv2(struct gpib_board *board, u8 status_byte, int new_reason_for_service);
-void ibrsc(struct gpib_board *board, int request_control);
+int ibrsc(struct gpib_board *board, int request_control);
 int ibsic(struct gpib_board *board, unsigned int usec_duration);
 int ibsre(struct gpib_board *board, int enable);
 int ibpad(struct gpib_board *board, unsigned int addr);

drivers/staging/gpib/include/gpib_types.h

···
 	 */
 	int (*go_to_standby)(struct gpib_board *board);
 	/* request/release control of the IFC and REN lines (system controller) */
-	void (*request_system_control)(struct gpib_board *board, int request_control);
+	int (*request_system_control)(struct gpib_board *board, int request_control);
 	/*
 	 * Asserts or de-asserts 'interface clear' (IFC) depending on
 	 * boolean value of 'assert'

drivers/staging/gpib/include/nec7210.h

···
 		    size_t length, size_t *bytes_written);
 int nec7210_take_control(struct gpib_board *board, struct nec7210_priv *priv, int syncronous);
 int nec7210_go_to_standby(struct gpib_board *board, struct nec7210_priv *priv);
-void nec7210_request_system_control(struct gpib_board *board,
-				    struct nec7210_priv *priv, int request_control);
+int nec7210_request_system_control(struct gpib_board *board,
+				   struct nec7210_priv *priv, int request_control);
 void nec7210_interface_clear(struct gpib_board *board, struct nec7210_priv *priv, int assert);
 void nec7210_remote_enable(struct gpib_board *board, struct nec7210_priv *priv, int enable);
 int nec7210_enable_eos(struct gpib_board *board, struct nec7210_priv *priv, u8 eos_bytes,

drivers/staging/gpib/include/tms9914.h

···
 int tms9914_take_control_workaround(struct gpib_board *board, struct tms9914_priv *priv,
 				    int syncronous);
 int tms9914_go_to_standby(struct gpib_board *board, struct tms9914_priv *priv);
-void tms9914_request_system_control(struct gpib_board *board, struct tms9914_priv *priv,
-				    int request_control);
+int tms9914_request_system_control(struct gpib_board *board, struct tms9914_priv *priv,
+				   int request_control);
 void tms9914_interface_clear(struct gpib_board *board, struct tms9914_priv *priv, int assert);
 void tms9914_remote_enable(struct gpib_board *board, struct tms9914_priv *priv, int enable);
 int tms9914_enable_eos(struct gpib_board *board, struct tms9914_priv *priv, u8 eos_bytes,

drivers/staging/gpib/ines/ines.h

···
 int ines_command(struct gpib_board *board, u8 *buffer, size_t length, size_t *bytes_written);
 int ines_take_control(struct gpib_board *board, int synchronous);
 int ines_go_to_standby(struct gpib_board *board);
-void ines_request_system_control(struct gpib_board *board, int request_control);
+int ines_request_system_control(struct gpib_board *board, int request_control);
 void ines_interface_clear(struct gpib_board *board, int assert);
 void ines_remote_enable(struct gpib_board *board, int enable);
 int ines_enable_eos(struct gpib_board *board, u8 eos_byte, int compare_8_bits);

drivers/staging/gpib/ines/ines_gpib.c

···
 	return nec7210_go_to_standby(board, &priv->nec7210_priv);
 }
 
-void ines_request_system_control(struct gpib_board *board, int request_control)
+int ines_request_system_control(struct gpib_board *board, int request_control)
 {
 	struct ines_priv *priv = board->private_data;
 
-	nec7210_request_system_control(board, &priv->nec7210_priv, request_control);
+	return nec7210_request_system_control(board, &priv->nec7210_priv, request_control);
 }
 
 void ines_interface_clear(struct gpib_board *board, int assert)

drivers/staging/gpib/lpvo_usb_gpib/lpvo_usb_gpib.c

···
 
 /* request_system_control */
 
-static void usb_gpib_request_system_control(struct gpib_board *board,
-					    int request_control)
+static int usb_gpib_request_system_control(struct gpib_board *board, int request_control)
 {
-	if (request_control)
-		set_bit(CIC_NUM, &board->status);
-	else
-		clear_bit(CIC_NUM, &board->status);
+	if (!request_control)
+		return -EINVAL;
 
+	set_bit(CIC_NUM, &board->status);
 	DIA_LOG(1, "done with %d -> %lx\n", request_control, board->status);
+	return 0;
 }
 
 /* take_control */

drivers/staging/gpib/nec7210/nec7210.c

···
 }
 EXPORT_SYMBOL(nec7210_go_to_standby);
 
-void nec7210_request_system_control(struct gpib_board *board, struct nec7210_priv *priv,
-				    int request_control)
+int nec7210_request_system_control(struct gpib_board *board, struct nec7210_priv *priv,
+				   int request_control)
 {
 	if (request_control == 0) {
 		write_byte(priv, AUX_CREN, AUXMR);
 		write_byte(priv, AUX_CIFC, AUXMR);
 		write_byte(priv, AUX_DSC, AUXMR);
 	}
+	return 0;
 }
 EXPORT_SYMBOL(nec7210_request_system_control);
 

drivers/staging/gpib/ni_usb/ni_usb_gpib.c

···
 	return 0;
 }
 
-static void ni_usb_request_system_control(struct gpib_board *board, int request_control)
+static int ni_usb_request_system_control(struct gpib_board *board, int request_control)
 {
 	int retval;
 	struct ni_usb_priv *ni_priv = board->private_data;
···
 	unsigned int ibsta;
 
 	if (!ni_priv->bus_interface)
-		return; // -ENODEV;
+		return -ENODEV;
 	usb_dev = interface_to_usbdev(ni_priv->bus_interface);
 	if (request_control) {
 		writes[i].device = NIUSB_SUBDEV_TNT4882;
···
 	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; // retval;
+		return retval;
 	}
 	if (!request_control)
 		ni_priv->ren_state = 0;
 	ni_usb_soft_update_status(board, ibsta, 0);
-	return; // 0;
+	return 0;
 }
 
 //FIXME maybe the interface should have a "pulse interface clear" function that can return an error?

drivers/staging/gpib/pc2/pc2_gpib.c

···
 	return nec7210_go_to_standby(board, &priv->nec7210_priv);
 }
 
-static void pc2_request_system_control(struct gpib_board *board, int request_control)
+static int pc2_request_system_control(struct gpib_board *board, int request_control)
 {
 	struct pc2_priv *priv = board->private_data;
 
-	nec7210_request_system_control(board, &priv->nec7210_priv, request_control);
+	return nec7210_request_system_control(board, &priv->nec7210_priv, request_control);
 }
 
 static void pc2_interface_clear(struct gpib_board *board, int assert)

drivers/staging/gpib/tms9914/tms9914.c

···
 }
 EXPORT_SYMBOL_GPL(tms9914_remote_enable);
 
-void tms9914_request_system_control(struct gpib_board *board, struct tms9914_priv *priv,
-				    int request_control)
+int tms9914_request_system_control(struct gpib_board *board, struct tms9914_priv *priv,
+				   int request_control)
 {
 	if (request_control) {
 		write_byte(priv, AUX_RQC, AUXCR);
···
 		clear_bit(CIC_NUM, &board->status);
 		write_byte(priv, AUX_RLC, AUXCR);
 	}
+	return 0;
 }
 EXPORT_SYMBOL_GPL(tms9914_request_system_control);
 

drivers/staging/gpib/tnt4882/tnt4882_gpib.c

···
 	return nec7210_go_to_standby(board, &priv->nec7210_priv);
 }
 
-static void tnt4882_request_system_control(struct gpib_board *board, int request_control)
+static int tnt4882_request_system_control(struct gpib_board *board, int request_control)
 {
 	struct tnt4882_priv *priv = board->private_data;
+	int retval;
 
 	if (request_control) {
 		tnt_writeb(priv, SETSC, CMDR);
 		udelay(1);
 	}
-	nec7210_request_system_control(board, &priv->nec7210_priv, request_control);
+	retval = nec7210_request_system_control(board, &priv->nec7210_priv, request_control);
 	if (!request_control) {
 		tnt_writeb(priv, CLRSC, CMDR);
 		udelay(1);
 	}
+	return retval;
 }
 
 static void tnt4882_interface_clear(struct gpib_board *board, int assert)