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iio: adc: ad7606_spi: add offload scan mask check

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Validate the scan mask when SPI offloading is being used.

Since this family of ADCs is simultaneous sampling, there isn't a way
to selectively disable channels when reading sample data. (Technically,
AD7616 has a sequencer so the driver could have some control, but that
is for another day).

For "regular" IIO triggered buffer reads, this isn't a problem and the
IIO core will demux the data and ignore data from disabled channels.
However, since SPI offloading is done completely in hardware, we don't
have a way to do the same. So before this patch, if less than all
channels were enabled, the data would be misplaced in the buffer.

By adding a check in update_scan_mode, we can fail to enable the buffer
instead of having bad data returned to userspace.

Fixes: e96d35faf3 ("iio: adc: ad7606: add SPI offload support")
Signed-off-by: David Lechner <dlechner@baylibre.com>
Reviewed-by: Andy Shevchenko <andy@kernel.org>
Reviewed-by: Nuno Sá <nuno.sa@analog.com>
Link: https://patch.msgid.link/20250502-iio-adc-ad7606_spi-fix-offload-scan-mask-check-v2-1-e70c6d71baa3@baylibre.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
This commit is contained in:
David Lechner 2025-05-02 10:42:16 -05:00 committed by Jonathan Cameron
parent 6eb974967a
commit 017294e5a6
1 changed files with 29 additions and 0 deletions
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29
drivers/iio/adc/ad7606_spi.c
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@ -5,6 +5,7 @@
* Copyright 2011 Analog Devices Inc.
*/
#include <linux/bitmap.h>
#include <linux/err.h>
#include <linux/math.h>
#include <linux/module.h>
@ -329,19 +330,44 @@ static int ad7606_spi_offload_probe(struct device *dev,
return 0;
}
static int ad7606_spi_update_scan_mode(struct iio_dev *indio_dev,
const unsigned long *scan_mask)
{
struct ad7606_state *st = iio_priv(indio_dev);
if (st->offload_en) {
unsigned int num_adc_ch = st->chip_info->num_adc_channels;
/*
* SPI offload requires that all channels are enabled since
* there isn't a way to selectively disable channels that get
* read (this is simultaneous sampling ADC) and the DMA buffer
* has no way of demuxing the data to filter out unwanted
* channels.
*/
if (bitmap_weight(scan_mask, num_adc_ch) != num_adc_ch)
return -EINVAL;
}
return 0;
}
static const struct ad7606_bus_ops ad7606_spi_bops = {
.offload_config = ad7606_spi_offload_probe,
.read_block = ad7606_spi_read_block,
.update_scan_mode = ad7606_spi_update_scan_mode,
};
static const struct ad7606_bus_ops ad7607_spi_bops = {
.offload_config = ad7606_spi_offload_probe,
.read_block = ad7606_spi_read_block14to16,
.update_scan_mode = ad7606_spi_update_scan_mode,
};
static const struct ad7606_bus_ops ad7608_spi_bops = {
.offload_config = ad7606_spi_offload_probe,
.read_block = ad7606_spi_read_block18to32,
.update_scan_mode = ad7606_spi_update_scan_mode,
};
static const struct ad7606_bus_ops ad7616_spi_bops = {
@ -350,6 +376,7 @@ static const struct ad7606_bus_ops ad7616_spi_bops = {
.reg_read = ad7606_spi_reg_read,
.reg_write = ad7606_spi_reg_write,
.rd_wr_cmd = ad7616_spi_rd_wr_cmd,
.update_scan_mode = ad7606_spi_update_scan_mode,
};
static const struct ad7606_bus_ops ad7606b_spi_bops = {
@ -359,6 +386,7 @@ static const struct ad7606_bus_ops ad7606b_spi_bops = {
.reg_write = ad7606_spi_reg_write,
.rd_wr_cmd = ad7606b_spi_rd_wr_cmd,
.sw_mode_config = ad7606b_sw_mode_config,
.update_scan_mode = ad7606_spi_update_scan_mode,
};
static const struct ad7606_bus_ops ad7606c_18_spi_bops = {
@ -368,6 +396,7 @@ static const struct ad7606_bus_ops ad7606c_18_spi_bops = {
.reg_write = ad7606_spi_reg_write,
.rd_wr_cmd = ad7606b_spi_rd_wr_cmd,
.sw_mode_config = ad7606b_sw_mode_config,
.update_scan_mode = ad7606_spi_update_scan_mode,
};
static const struct ad7606_bus_info ad7605_4_bus_info = {