staging: comedi: ni_tio: remove BUG() checks for ni_tio_get_clock_src()

This function calls some helper functions to convert the counter variant
specific clock select bits into the generic enum ni_gpct_clock_source_bits
equivelent. These helper functions currently BUG() if the clock select
bits are invalid.

It then calls ni_tio_clock_period_ps() to figure out the clock period
based on the generic clock source. This function could also BUG() if
the prescale bits are invalid.

In reality this should never happen but refactor the code to return
-EINVAL instead and remove the BUG() checks.

These functions are also called by ni_tio_set_sync_mode(). When this
function is called by ni_tio_set_clock_src() the counter select bits
have already been validated.

Signed-off-by: H Hartley Sweeten <[e-mail]>
Reviewed-by: Ian Abbott <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/staging/comedi/drivers/ni_tio.c

···
 	ni_tio_write(counter, GI_RESET(cidx), NITIO_RESET_REG(cidx));
 }
 
-static u64 ni_tio_clock_period_ps(const struct ni_gpct *counter,
-				  unsigned int generic_clock_source)
+static int ni_tio_clock_period_ps(const struct ni_gpct *counter,
+				  unsigned int generic_clock_source,
+				  u64 *period_ps)
 {
 	u64 clock_period_ps;
 
···
 		clock_period_ps *= 8;
 		break;
 	default:
-		BUG();
-		break;
+		return -EINVAL;
 	}
-	return clock_period_ps;
+	*period_ps = clock_period_ps;
+	return 0;
 }
 
 static void ni_tio_set_bits_transient(struct ni_gpct *counter,
···
 	return bits;
 }
 
-static unsigned int ni_m_series_clock_src_select(const struct ni_gpct *counter)
+static int ni_m_series_clock_src_select(const struct ni_gpct *counter,
+					unsigned int *clk_src)
 {
 	struct ni_gpct_device *counter_dev = counter->counter_dev;
 	unsigned int cidx = counter->counter_index;
···
 		}
 		if (i <= NI_M_MAX_PFI_CHAN)
 			break;
-		BUG();
-		break;
+		return -EINVAL;
 	}
 	clock_source |= ni_tio_clock_src_modifiers(counter);
-	return clock_source;
+	*clk_src = clock_source;
+	return 0;
 }
 
-static unsigned int ni_660x_clock_src_select(const struct ni_gpct *counter)
+static int ni_660x_clock_src_select(const struct ni_gpct *counter,
+				    unsigned int *clk_src)
 {
 	unsigned int clock_source = 0;
 	unsigned int cidx = counter->counter_index;
···
 		}
 		if (i <= NI_660X_MAX_SRC_PIN)
 			break;
-		BUG();
-		break;
+		return -EINVAL;
 	}
 	clock_source |= ni_tio_clock_src_modifiers(counter);
-	return clock_source;
+	*clk_src = clock_source;
+	return 0;
 }
 
-static unsigned int
-ni_tio_generic_clock_src_select(const struct ni_gpct *counter)
+static int ni_tio_generic_clock_src_select(const struct ni_gpct *counter,
+					   unsigned int *clk_src)
 {
 	switch (counter->counter_dev->variant) {
 	case ni_gpct_variant_e_series:
 	case ni_gpct_variant_m_series:
 	default:
-		return ni_m_series_clock_src_select(counter);
+		return ni_m_series_clock_src_select(counter, clk_src);
 	case ni_gpct_variant_660x:
-		return ni_660x_clock_src_select(counter);
+		return ni_660x_clock_src_select(counter, clk_src);
 	}
 }
 
···
 	unsigned int bits = 0;
 	unsigned int reg;
 	unsigned int mode;
+	unsigned int clk_src;
 	u64 ps;
 	bool force_alt_sync;
 
···
 		break;
 	}
 
-	ps = ni_tio_clock_period_ps(counter,
-				    ni_tio_generic_clock_src_select(counter));
+	ni_tio_generic_clock_src_select(counter, &clk_src);
+	ni_tio_clock_period_ps(counter, clk_src, &ps);
 
 	/*
 	 * It's not clear what we should do if clock_period is unknown, so we
···
 	return 0;
 }
 
-static void ni_tio_get_clock_src(struct ni_gpct *counter,
-				 unsigned int *clock_source,
-				 unsigned int *period_ns)
+static int ni_tio_get_clock_src(struct ni_gpct *counter,
+				unsigned int *clock_source,
+				unsigned int *period_ns)
 {
 	u64 temp64;
+	int ret;
 
-	*clock_source = ni_tio_generic_clock_src_select(counter);
-	temp64 = ni_tio_clock_period_ps(counter, *clock_source);
+	ret = ni_tio_generic_clock_src_select(counter, clock_source);
+	if (ret)
+		return ret;
+	ret = ni_tio_clock_period_ps(counter, *clock_source, &temp64);
+	if (ret)
+		return ret;
 	do_div(temp64, 1000);	/* ps to ns */
 	*period_ns = temp64;
+	return 0;
 }
 
 static int ni_660x_set_gate(struct ni_gpct *counter, unsigned int gate_source)
···
 		ret = ni_tio_set_clock_src(counter, data[1], data[2]);
 		break;
 	case INSN_CONFIG_GET_CLOCK_SRC:
-		ni_tio_get_clock_src(counter, &data[1], &data[2]);
+		ret = ni_tio_get_clock_src(counter, &data[1], &data[2]);
 		break;
 	case INSN_CONFIG_SET_GATE_SRC:
 		ret = ni_tio_set_gate_src(counter, data[1], data[2]);