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iio: adc: ti-ads1015: Add static assert to test if shifted realbits fit into storagebits

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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@denx.de>
Reviewed-by: Andy Shevchenko <andy@kernel.org>
Cc: Daniel Baluta <daniel.baluta@nxp.com>
Link: https://lore.kernel.org/r/20220328194725.149150-7-marex@denx.de
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
This commit is contained in:
Marek Vasut 2022-03-28 21:47:22 +02:00 • committed by Jonathan Cameron
parent f1c9ce0ced
commit 3139ff24e2
1 changed files with 24 additions and 2 deletions
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26
drivers/iio/adc/ti-ads1015.c
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@ -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, \
}, \