Add compile-time static_assert wrapper to verify that shifted realbits
fit into storagebits. The macro is implemented in a more generic way so
it can be used to verify other values if required.
Signed-off-by: Marek Vasut <marex@xxxxxxx>
Cc: Andy Shevchenko <andy@xxxxxxxxxx>
Cc: Daniel Baluta <daniel.baluta@xxxxxxx>
Cc: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
---
V2: New patch
V3: No change
V4: No change
V5: No change
---
drivers/iio/adc/ti-ads1015.c | 26 ++++++++++++++++++++++++--
1 file changed, 24 insertions(+), 2 deletions(-)
diff --git a/drivers/iio/adc/ti-ads1015.c b/drivers/iio/adc/ti-ads1015.c
index 51ab8bb3d9f1d..73d848804a12d 100644
--- a/drivers/iio/adc/ti-ads1015.c
+++ b/drivers/iio/adc/ti-ads1015.c
@@ -135,6 +135,28 @@ static const struct iio_event_spec ads1015_events[] = {
},
};
+/*
+ * Compile-time check whether _fitbits can accommodate up to _testbits
+ * bits. Returns _fitbits on success, fails to compile otherwise.
+ *
+ * The test works such that it multiplies constant _fitbits by constant
+ * double-negation of size of a non-empty structure, i.e. it multiplies
+ * constant _fitbits by constant 1 in each successful compilation case.
+ * The non-empty structure may contain C11 _Static_assert(), make use of
+ * this and place the kernel variant of static assert in there, so that
+ * it performs the compile-time check for _testbits <= _fitbits. Note
+ * that it is not possible to directly use static_assert in compound
+ * statements, hence this convoluted construct.
+ */
+#define FIT_CHECK(_testbits, _fitbits) \
+ ( \
+ (_fitbits) * \
+ !!sizeof(struct { \
+ static_assert((_testbits) <= (_fitbits)); \
+ int pad; \
+ }) \
+ )
+
#define ADS1015_V_CHAN(_chan, _addr, _realbits, _shift, _event_spec, _num_event_specs) { \
.type = IIO_VOLTAGE, \
.indexed = 1, \
@@ -147,7 +169,7 @@ static const struct iio_event_spec ads1015_events[] = {
.scan_type = { \
.sign = 's', \
.realbits = (_realbits), \
- .storagebits = 16, \
+ .storagebits = FIT_CHECK((_realbits) + (_shift), 16), \
.shift = (_shift), \
.endianness = IIO_CPU, \
}, \
@@ -170,7 +192,7 @@ static const struct iio_event_spec ads1015_events[] = {
.scan_type = { \
.sign = 's', \
.realbits = (_realbits), \
- .storagebits = 16, \
+ .storagebits = FIT_CHECK((_realbits) + (_shift), 16), \
.shift = (_shift), \
.endianness = IIO_CPU, \
}, \
--
2.35.1
