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Message-ID: <20250723114645.596648-1-akshayaj.lkd@gmail.com>
Date: Wed, 23 Jul 2025 17:16:38 +0530
From: Akshay Jindal <akshayaj.lkd@...il.com>
To: anshulusr@...il.com,
jic23@...nel.org,
dlechner@...libre.com,
nuno.sa@...log.com,
andy@...nel.org
Cc: Akshay Jindal <akshayaj.lkd@...il.com>,
shuah@...nel.org,
linux-iio@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: [PATCH] iio: light: ltr390: Add debugfs register access support
Add support for debugfs_reg_access through the driver's iio_info structure
to enable low-level register read/write access for debugging.
Signed-off-by: Akshay Jindal <akshayaj.lkd@...il.com>
---
Testing details:
================
-> Tested on Raspberrypi 4B. Follow for more details.
akshayajpi@...pberrypi:~ $ uname -r
6.12.35-v8+
akshayajpi@...pberrypi:~ $ uname -a
Linux raspberrypi 6.12.35-v8+ #5 SMP PREEMPT Tue Jul 15 17:38:06 IST 2025 aarch64 GNU/Linux
-> Sensor Detection, overlaying of device tree and Driver loading
akshayajpi@...pberrypi:~ $ i2cdetect -y 1
0 1 2 3 4 5 6 7 8 9 a b c d e f
00: -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- -- -- 53 -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --
akshayajpi@...pberrypi:~ $ sudo dtoverlay i2c-sensor ltr390
akshayajpi@...pberrypi:~ $ lsmod|grep ltr390
ltr390 16384 0
industrialio 110592 1 ltr390
regmap_i2c 12288 1 ltr390
1. Disable sensor via debugfs, verify from i2cget and debugfs.
akshayajpi@...pberrypi:/sys/kernel/debug/iio/iio:device0 $ echo 0x0 | sudo tee direct_reg_access
0x0
akshayajpi@...pberrypi:/sys/kernel/debug/iio/iio:device0 $ cat direct_reg_access
0x2
akshayajpi@...pberrypi:/sys/kernel/debug/iio/iio:device0 $ echo 0x0 0x0 | sudo tee direct_reg_access
0x0 0x0
akshayajpi@...pberrypi:/sys/kernel/debug/iio/iio:device0 $ cat direct_reg_access
0x0
akshayajpi@...pberrypi:/sys/kernel/debug/iio/iio:device0 $ i2cget -f -y 1 0x53 0x0
0x00
2. Disable sensor via debugfs and read data status via debugfs.
akshayajpi@...pberrypi:/sys/kernel/debug/iio/iio:device0 $ cat /sys/bus/iio/devices/iio\:device0/in_illuminance_raw
715
akshayajpi@...pberrypi:/sys/kernel/debug/iio/iio:device0 $ cat /sys/bus/iio/devices/iio\:device0/in_illuminance_raw
715
akshayajpi@...pberrypi:/sys/kernel/debug/iio/iio:device0 $ cat /sys/bus/iio/devices/iio\:device0/in_illuminance_raw
715
akshayajpi@...pberrypi:/sys/kernel/debug/iio/iio:device0 $ i2cget -f -y 1 0x53 0x7
0x28
akshayajpi@...pberrypi:/sys/kernel/debug/iio/iio:device0 $ i2cget -f -y 1 0x53 0x7
0x00
akshayajpi@...pberrypi:/sys/kernel/debug/iio/iio:device0 $ echo 0x7 | sudo tee direct_reg_access
0x7
akshayajpi@...pberrypi:/sys/kernel/debug/iio/iio:device0 $ cat direct_reg_access
0x0
3. Re-enable sensor via debugfs and read data status via debugfs.
akshayajpi@...pberrypi:/sys/kernel/debug/iio/iio:device0 $ echo 0x0 0x2 | sudo tee direct_reg_access
0x0 0x2
akshayajpi@...pberrypi:/sys/kernel/debug/iio/iio:device0 $ cat direct_reg_access
0x2
akshayajpi@...pberrypi:/sys/kernel/debug/iio/iio:device0 $ cat /sys/bus/iio/devices/iio\:device0/in_illuminance_raw
715
akshayajpi@...pberrypi:/sys/kernel/debug/iio/iio:device0 $ cat /sys/bus/iio/devices/iio\:device0/in_illuminance_raw
718
akshayajpi@...pberrypi:/sys/kernel/debug/iio/iio:device0 $ cat /sys/bus/iio/devices/iio\:device0/in_illuminance_raw
727
akshayajpi@...pberrypi:/sys/kernel/debug/iio/iio:device0 $ echo 0x7 | sudo tee direct_reg_access
0x7
akshayajpi@...pberrypi:/sys/kernel/debug/iio/iio:device0 $ cat direct_reg_access
0x8
4. Enable interrupts via sysfs and verify via debugfs.
akshayajpi@...pberrypi:/sys/kernel/debug/iio/iio:device0 $ echo 1 | sudo tee /sys/bus/iio/devices/iio\:device0/events/in_illuminance_thresh_either_en
1
akshayajpi@...pberrypi:/sys/kernel/debug/iio/iio:device0 $ i2cget -f -y 1 0x53 0x19
0x14
akshayajpi@...pberrypi:/sys/kernel/debug/iio/iio:device0 $ echo 0x19 | sudo tee direct_reg_access
0x19
akshayajpi@...pberrypi:/sys/kernel/debug/iio/iio:device0 $ cat direct_reg_access
0x14
5. Write falling threshold via debugfs, verify the threshold written via sysfs.
akshayajpi@...pberrypi:/sys/kernel/debug/iio/iio:device0 $ echo 0x24 0x32 | sudo tee direct_reg_access
0x24 0x32
akshayajpi@...pberrypi:/sys/kernel/debug/iio/iio:device0 $ cat direct_reg_access
0x32
akshayajpi@...pberrypi:/sys/kernel/debug/iio/iio:device0 $ echo 0x25 0x0 | sudo tee direct_reg_access
0x25 0x0
akshayajpi@...pberrypi:/sys/kernel/debug/iio/iio:device0 $ cat direct_reg_access
0x0
akshayajpi@...pberrypi:/sys/kernel/debug/iio/iio:device0 $ echo 0x26 0x0 | sudo tee direct_reg_access
0x26 0x0
akshayajpi@...pberrypi:/sys/kernel/debug/iio/iio:device0 $ cat direct_reg_access
0x0
akshayajpi@...pberrypi:/sys/kernel/debug/iio/iio:device0 $ cat /sys/bus/iio/devices/iio\:device0/events/in_illuminance_thresh_falling_value
50
final value = 0x0 << 16 | 0x0 << 8 | 0x32 = 50
6. Block light and verify interrupts getting generated.
-> Before blocking light
cat /proc/interrupts|grep ltr390
58: 0 0 0 0 pinctrl-bcm2835 4 Edge ltr390_thresh_event
->After blocking light
58: 92 0 0 0 pinctrl-bcm2835 4 Edge ltr390_thresh_event
7. write value to a non-writeable reg via debugfs.
-> LTR390_ALS_DATA_0|1|2 are non-writeable registers. Writing to them gives I/O error as expected.
akshayajpi@...pberrypi:/sys/kernel/debug/iio/iio:device0 $ echo 0xd 0x1 | sudo tee direct_reg_access
0xd 0x1
tee: direct_reg_access: Input/output error
akshayajpi@...pberrypi:/sys/kernel/debug/iio/iio:device0 $ echo 0xe 0x1 | sudo tee direct_reg_access
0xe 0x1
tee: direct_reg_access: Input/output error
akshayajpi@...pberrypi:/sys/kernel/debug/iio/iio:device0 $ echo 0xf 0x1 | sudo tee direct_reg_access
0xf 0x1
tee: direct_reg_access: Input/output error
8. read value from a non-readable reg via debugfs.
akshayajpi@...pberrypi:/sys/kernel/debug/iio/iio:device0 $ echo 0x2 |sudo tee direct_reg_access
0x2
akshayajpi@...pberrypi:/sys/kernel/debug/iio/iio:device0 $ cat direct_reg_access
cat: direct_reg_access: Input/output error
9. do simple raw reads from debugfs.
-> reading raw value via sysfs:
akshayajpi@...pberrypi:/sys/kernel/debug/iio/iio:device0 $ cat /sys/bus/iio/devices/iio\:device0/in_illuminance_raw
705
akshayajpi@...pberrypi:/sys/kernel/debug/iio/iio:device0 $ cat /sys/bus/iio/devices/iio\:device0/in_illuminance_raw
695
akshayajpi@...pberrypi:/sys/kernel/debug/iio/iio:device0 $ cat /sys/bus/iio/devices/iio\:device0/in_illuminance_raw
711
-> reading via debugfs (should be in the same ballpark of sysfs)
akshayajpi@...pberrypi:/sys/kernel/debug/iio/iio:device0 $ echo 0xd | sudo tee direct_reg_access
0xd
akshayajpi@...pberrypi:/sys/kernel/debug/iio/iio:device0 $ cat direct_reg_access
0xC7
akshayajpi@...pberrypi:/sys/kernel/debug/iio/iio:device0 $ echo 0xe | sudo tee direct_reg_access
0xe
akshayajpi@...pberrypi:/sys/kernel/debug/iio/iio:device0 $ cat direct_reg_access
0x2
akshayajpi@...pberrypi:/sys/kernel/debug/iio/iio:device0 $ echo 0xf | sudo tee direct_reg_access
0xf
akshayajpi@...pberrypi:/sys/kernel/debug/iio/iio:device0 $ cat direct_reg_access
0x0
final value = 0x0 << 16 | 0x2 << 8 | 0xc7 = 711
10. Testing reads on registers beyond max_register.
akshayajpi@...pberrypi:/sys/kernel/debug/iio/iio:device0 $ echo 0x27 | sudo tee direct_reg_access
0x27
akshayajpi@...pberrypi:/sys/kernel/debug/iio/iio:device0 $ cat direct_reg_access
cat: direct_reg_access: Input/output error
akshayajpi@...pberrypi:/sys/kernel/debug/iio/iio:device0 $ echo 0x28 | sudo tee direct_reg_access
0x28
akshayajpi@...pberrypi:/sys/kernel/debug/iio/iio:device0 $ cat direct_reg_access
cat: direct_reg_access: Input/output error
drivers/iio/light/ltr390.c | 99 ++++++++++++++++++++++++++++++++++----
1 file changed, 89 insertions(+), 10 deletions(-)
diff --git a/drivers/iio/light/ltr390.c b/drivers/iio/light/ltr390.c
index ee59bbb8aa09..1f6ee0fd6d19 100644
--- a/drivers/iio/light/ltr390.c
+++ b/drivers/iio/light/ltr390.c
@@ -38,12 +38,20 @@
#define LTR390_ALS_UVS_GAIN 0x05
#define LTR390_PART_ID 0x06
#define LTR390_MAIN_STATUS 0x07
-#define LTR390_ALS_DATA 0x0D
-#define LTR390_UVS_DATA 0x10
+#define LTR390_ALS_DATA_0 0x0D
+#define LTR390_ALS_DATA_1 0x0E
+#define LTR390_ALS_DATA_2 0x0F
+#define LTR390_UVS_DATA_0 0x10
+#define LTR390_UVS_DATA_1 0x11
+#define LTR390_UVS_DATA_2 0x12
#define LTR390_INT_CFG 0x19
#define LTR390_INT_PST 0x1A
-#define LTR390_THRESH_UP 0x21
-#define LTR390_THRESH_LOW 0x24
+#define LTR390_THRESH_UP_0 0x21
+#define LTR390_THRESH_UP_1 0x22
+#define LTR390_THRESH_UP_2 0x23
+#define LTR390_THRESH_LOW_0 0x24
+#define LTR390_THRESH_LOW_1 0x25
+#define LTR390_THRESH_LOW_2 0x26
#define LTR390_PART_NUMBER_ID 0xb
#define LTR390_ALS_UVS_GAIN_MASK GENMASK(2, 0)
@@ -98,11 +106,62 @@ struct ltr390_data {
int int_time_us;
};
+static bool ltr390_is_readable_reg(struct device *dev, unsigned int reg)
+{
+ switch (reg) {
+ case LTR390_MAIN_CTRL:
+ case LTR390_ALS_UVS_MEAS_RATE:
+ case LTR390_ALS_UVS_GAIN:
+ case LTR390_PART_ID:
+ case LTR390_MAIN_STATUS:
+ case LTR390_ALS_DATA_0:
+ case LTR390_ALS_DATA_1:
+ case LTR390_ALS_DATA_2:
+ case LTR390_UVS_DATA_0:
+ case LTR390_UVS_DATA_1:
+ case LTR390_UVS_DATA_2:
+ case LTR390_INT_CFG:
+ case LTR390_INT_PST:
+ case LTR390_THRESH_UP_0:
+ case LTR390_THRESH_UP_1:
+ case LTR390_THRESH_UP_2:
+ case LTR390_THRESH_LOW_0:
+ case LTR390_THRESH_LOW_1:
+ case LTR390_THRESH_LOW_2:
+ return true;
+ default:
+ return false;
+ }
+}
+
+static bool ltr390_is_writeable_reg(struct device *dev, unsigned int reg)
+{
+ switch (reg) {
+ case LTR390_MAIN_CTRL:
+ case LTR390_ALS_UVS_MEAS_RATE:
+ case LTR390_ALS_UVS_GAIN:
+ case LTR390_INT_CFG:
+ case LTR390_INT_PST:
+ case LTR390_THRESH_UP_0:
+ case LTR390_THRESH_UP_1:
+ case LTR390_THRESH_UP_2:
+ case LTR390_THRESH_LOW_0:
+ case LTR390_THRESH_LOW_1:
+ case LTR390_THRESH_LOW_2:
+ return true;
+ default:
+ return false;
+ }
+}
+
static const struct regmap_config ltr390_regmap_config = {
.name = "ltr390",
.reg_bits = 8,
.reg_stride = 1,
.val_bits = 8,
+ .max_register = LTR390_THRESH_LOW_2,
+ .readable_reg = ltr390_is_readable_reg,
+ .writeable_reg = ltr390_is_writeable_reg,
};
/* Sampling frequency is in mili Hz and mili Seconds */
@@ -194,7 +253,7 @@ static int ltr390_read_raw(struct iio_dev *iio_device,
if (ret < 0)
return ret;
- ret = ltr390_register_read(data, LTR390_UVS_DATA);
+ ret = ltr390_register_read(data, LTR390_UVS_DATA_0);
if (ret < 0)
return ret;
break;
@@ -204,7 +263,7 @@ static int ltr390_read_raw(struct iio_dev *iio_device,
if (ret < 0)
return ret;
- ret = ltr390_register_read(data, LTR390_ALS_DATA);
+ ret = ltr390_register_read(data, LTR390_ALS_DATA_0);
if (ret < 0)
return ret;
break;
@@ -454,14 +513,14 @@ static int ltr390_read_threshold(struct iio_dev *indio_dev,
switch (dir) {
case IIO_EV_DIR_RISING:
- ret = ltr390_register_read(data, LTR390_THRESH_UP);
+ ret = ltr390_register_read(data, LTR390_THRESH_UP_0);
if (ret < 0)
return ret;
*val = ret;
return IIO_VAL_INT;
case IIO_EV_DIR_FALLING:
- ret = ltr390_register_read(data, LTR390_THRESH_LOW);
+ ret = ltr390_register_read(data, LTR390_THRESH_LOW_0);
if (ret < 0)
return ret;
*val = ret;
@@ -480,10 +539,10 @@ static int ltr390_write_threshold(struct iio_dev *indio_dev,
guard(mutex)(&data->lock);
switch (dir) {
case IIO_EV_DIR_RISING:
- return regmap_bulk_write(data->regmap, LTR390_THRESH_UP, &val, 3);
+ return regmap_bulk_write(data->regmap, LTR390_THRESH_UP_0, &val, 3);
case IIO_EV_DIR_FALLING:
- return regmap_bulk_write(data->regmap, LTR390_THRESH_LOW, &val, 3);
+ return regmap_bulk_write(data->regmap, LTR390_THRESH_LOW_0, &val, 3);
default:
return -EINVAL;
@@ -586,6 +645,25 @@ static int ltr390_write_event_config(struct iio_dev *indio_dev,
}
}
+static int ltr390_debugfs_reg_access(struct iio_dev *indio_dev,
+ unsigned int reg, unsigned int writeval,
+ unsigned int *readval)
+{
+ int ret;
+ struct ltr390_data *data = iio_priv(indio_dev);
+
+ guard(mutex)(&data->lock);
+
+ if (!readval)
+ return regmap_write(data->regmap, reg, writeval);
+
+ ret = regmap_read(data->regmap, reg, readval);
+ if (ret < 0)
+ return ret;
+
+ return 0;
+}
+
static const struct iio_info ltr390_info = {
.read_raw = ltr390_read_raw,
.write_raw = ltr390_write_raw,
@@ -594,6 +672,7 @@ static const struct iio_info ltr390_info = {
.read_event_config = ltr390_read_event_config,
.write_event_value = ltr390_write_event_value,
.write_event_config = ltr390_write_event_config,
+ .debugfs_reg_access = ltr390_debugfs_reg_access,
};
static irqreturn_t ltr390_interrupt_handler(int irq, void *private)
--
2.43.0
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