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From: Bart Van Assche <bvanassche@acm.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Christoph Hellwig <hch@lst.de>,
	"Martin K . Petersen" <martin.petersen@oracle.com>,
	linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org,
	Bart Van Assche <bvanassche@acm.org>,
	Jonathan Cameron <jic23@kernel.org>,
	Hartmut Knaack <knaack.h@gmx.de>,
	Lars-Peter Clausen <lars@metafoo.de>,
	Peter Meerwald-Stadler <pmeerw@pmeerw.net>
Subject: [PATCH 4/9] drivers/iio: Sign extend without triggering implementation-defined behavior
Date: Mon, 28 Oct 2019 13:06:55 -0700	[thread overview]
Message-ID: <20191028200700.213753-5-bvanassche@acm.org> (raw)
In-Reply-To: <20191028200700.213753-1-bvanassche@acm.org>

From the C standard: "The result of E1 >> E2 is E1 right-shifted E2 bit
positions. If E1 has an unsigned type or if E1 has a signed type and a
nonnegative value, the value of the result is the integral part of the
quotient of E1 / 2E2 . If E1 has a signed type and a negative value, the
resulting value is implementation-defined."

Hence use sign_extend_24_to_32() instead of "<< 8 >> 8".

Cc: Jonathan Cameron <jic23@kernel.org>
Cc: Hartmut Knaack <knaack.h@gmx.de>
Cc: Lars-Peter Clausen <lars@metafoo.de>
Cc: Peter Meerwald-Stadler <pmeerw@pmeerw.net>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
 drivers/iio/common/st_sensors/st_sensors_core.c | 7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/drivers/iio/common/st_sensors/st_sensors_core.c b/drivers/iio/common/st_sensors/st_sensors_core.c
index 4a3064fb6cd9..94a9cec69cd7 100644
--- a/drivers/iio/common/st_sensors/st_sensors_core.c
+++ b/drivers/iio/common/st_sensors/st_sensors_core.c
@@ -21,11 +21,6 @@
 
 #include "st_sensors_core.h"
 
-static inline u32 st_sensors_get_unaligned_le24(const u8 *p)
-{
-	return (s32)((p[0] | p[1] << 8 | p[2] << 16) << 8) >> 8;
-}
-
 int st_sensors_write_data_with_mask(struct iio_dev *indio_dev,
 				    u8 reg_addr, u8 mask, u8 data)
 {
@@ -556,7 +551,7 @@ static int st_sensors_read_axis_data(struct iio_dev *indio_dev,
 	else if (byte_for_channel == 2)
 		*data = (s16)get_unaligned_le16(outdata);
 	else if (byte_for_channel == 3)
-		*data = (s32)st_sensors_get_unaligned_le24(outdata);
+		*data = get_unaligned_signed_le24(outdata);
 
 st_sensors_free_memory:
 	kfree(outdata);
-- 
2.24.0.rc0.303.g954a862665-goog


  parent reply	other threads:[~2019-10-28 20:07 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-28 20:06 [PATCH 0/9] Consolidate {get,put}_unaligned_[bl]e24() definitions Bart Van Assche
2019-10-28 20:06 ` [PATCH 1/9] linux/unaligned/byteshift.h: Remove superfluous casts Bart Van Assche
2019-10-28 20:06 ` [PATCH 2/9] c6x: Include <linux/unaligned/generic.h> instead of duplicating it Bart Van Assche
2019-11-07  3:09   ` Bart Van Assche
2019-11-07 13:54   ` Mark Salter
2019-10-28 20:06 ` [PATCH 3/9] treewide: Consolidate {get,put}_unaligned_[bl]e24() definitions Bart Van Assche
2019-10-28 20:06 ` Bart Van Assche [this message]
2019-10-30 19:43   ` [PATCH 4/9] drivers/iio: Sign extend without triggering implementation-defined behavior Jonathan Cameron
2019-10-30 20:02   ` Peter Zijlstra
2019-10-30 22:13     ` Douglas Gilbert
2019-10-31 17:55       ` Bart Van Assche
2019-10-28 20:06 ` [PATCH 5/9] scsi/st: Use get_unaligned_signed_be24() Bart Van Assche
2019-10-28 20:06 ` [PATCH 6/9] scsi/trace: Use get_unaligned_be*() Bart Van Assche
2019-10-28 20:06 ` [PATCH 7/9] arm/ecard: Use get_unaligned_le{16,24}() Bart Van Assche
2019-10-28 20:06 ` [PATCH 8/9] IB/qib: Sign extend without triggering implementation-defined behavior Bart Van Assche
2019-10-28 20:07 ` [PATCH 9/9] ASoC/fsl_spdif: Use put_unaligned_be24() instead of open-coding it Bart Van Assche
2019-10-28 20:24   ` Mark Brown
2019-10-28 20:49     ` Bart Van Assche
2019-10-28 21:52 ` [PATCH 0/9] Consolidate {get,put}_unaligned_[bl]e24() definitions Peter Zijlstra
2019-10-28 22:02   ` Bart Van Assche
2019-10-29  1:10 ` Douglas Gilbert

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