Commit 3139ff24 authored by Marek Vasut's avatar Marek Vasut Committed by Jonathan Cameron
Browse files

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



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: default avatarMarek Vasut <marex@denx.de>
Reviewed-by: default avatarAndy 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: default avatarJonathan Cameron <Jonathan.Cameron@huawei.com>
parent f1c9ce0c

drivers/iio/adc/ti-ads1015.c

+24 −2
Original line number Diff line number Diff line
@@ -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,				\

	},							\