patch "drivers: iio: adc: ltc2497: fix LSB shift" added to char-misc-linus

This is a note to let you know that I've just added the patch titled

drivers: iio: adc: ltc2497: fix LSB shift

to my char-misc git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc.git
in the char-misc-linus branch.

The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)

The patch will hopefully also be merged in Linus's tree for the next -rc kernel release.

If you have any questions about this process, please let me know.

From 6327a930ab7bfa1ab33bcdffd5f5f4b1e7131504 Mon Sep 17 00:00:00 2001
From: Ian Ray <[email protected]>
Date: Fri, 27 Jan 2023 14:57:14 +0200
Subject: drivers: iio: adc: ltc2497: fix LSB shift

Correct the "sub_lsb" shift for the ltc2497 and drop the sub_lsb element which is now constant.

An earlier version of the code shifted by 14 but this was a consequence of reading three bytes into a __be32 buffer and using be32_to_cpu(), so eight extra bits needed to be skipped. Now we use get_unaligned_be24() and thus the additional skip is wrong.

---
 drivers/iio/adc/ltc2497.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

index 17370c5eb6fe..ec198c6f13d6 100644
@@ -28,7 +28,6 @@ struct ltc2497_driverdata {
 	struct ltc2497core_driverdata common_ddata;
 	struct i2c_client *client;
 	u32 recv_size;
-	u32 sub_lsb;
 	/*
 	 * DMA (thus cache coherency maintenance) may require the
 	 * transfer buffers to live in their own cache lines.

@@ -65,10 +64,10 @@ static int ltc2497_result_and_measure(struct ltc2497core_driverdata *ddata,
 		 * equivalent to a sign extension.
 		 */
 		if (st->recv_size == 3) {
-			*val = (get_unaligned_be24(st->data.d8) >> st->sub_lsb)
+			*val = (get_unaligned_be24(st->data.d8) >> 6)
 				- BIT(ddata->chip_info->resolution + 1);
 		} else {
-			*val = (be32_to_cpu(st->data.d32) >> st->sub_lsb)
+			*val = (be32_to_cpu(st->data.d32) >> 6)
 				- BIT(ddata->chip_info->resolution + 1);
 		}
 

@@ -122,7 +121,6 @@ static int ltc2497_probe(struct i2c_client *client)
 	st->common_ddata.chip_info = chip_info;
 
 	resolution = chip_info->resolution;
-	st->sub_lsb = 31 - (resolution + 1);
 	st->recv_size = BITS_TO_BYTES(resolution) + 1;
 
 	return ltc2497core_probe(dev, indio_dev);

2.40.0