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[PATCH v2] iio: light: ltr390: Add debugfs register access support

Akshay Jindal posted 1 patch 4 months, 4 weeks ago
There is a newer version of this series
drivers/iio/light/ltr390.c | 55 ++++++++++++++++++++++++++++++++++++++
1 file changed, 55 insertions(+)
[PATCH v2] iio: light: ltr390: Add debugfs register access support
Posted by Akshay Jindal 4 months, 4 weeks ago 
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@gmail.com>
---

Changes since v1:
=================
- Replaced _[0|1|2] macros with a respective common parameterized macro.
- Retained base macros to avoid churn.
- Swapped regmap_write with regmap_read to avoid negate operator.
- Simplified debugfs function by directly returning return value of
  regmap_[read|write].
- Replaced [readable|writeable]_reg with regmap ranges by using
  [rd|wr]_table property of regmap_config.
 
Testing details(updated):
========================
-> Tested on Raspberrypi 4B. Follow for more details.

akshayajpi@raspberrypi:~ $ uname -r
6.12.35-v8+
akshayajpi@raspberrypi:~ $ 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@raspberrypi:~ $ 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@raspberrypi:~ $ sudo dtoverlay i2c-sensor ltr390
akshayajpi@raspberrypi:~ $ 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@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ echo 0x0 | sudo tee direct_reg_access
0x0
akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ cat direct_reg_access
0x2
akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ echo 0x0 0x0 | sudo tee direct_reg_access
0x0 0x0
akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ cat direct_reg_access
0x0
akshayajpi@raspberrypi:/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@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ cat /sys/bus/iio/devices/iio\:device0/in_illuminance_raw
603
akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ cat /sys/bus/iio/devices/iio\:device0/in_illuminance_raw
603
akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ cat /sys/bus/iio/devices/iio\:device0/in_illuminance_raw
603
akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ i2cget -f -y 1 0x53 0x7
0x28
akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ i2cget -f -y 1 0x53 0x7
0x00
akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ echo 0x7 | sudo tee direct_reg_access
0x7
akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ cat direct_reg_access
0x0

3. Re-enable sensor via debugfs and read data status via debugfs.
akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ echo 0x0 0x2 | sudo tee direct_reg_access
0x0 0x2
akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ cat direct_reg_access
0x2
akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ cat /sys/bus/iio/devices/iio\:device0/in_illuminance_raw
608
akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ cat /sys/bus/iio/devices/iio\:device0/in_illuminance_raw
614
akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ cat /sys/bus/iio/devices/iio\:device0/in_illuminance_raw
601
akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ echo 0x7 | sudo tee direct_reg_access
0x7
akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ cat direct_reg_access
0x8

4. Enable interrupts via sysfs and verify via debugfs.
akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ echo 1 | sudo tee /sys/bus/iio/devices/iio\:device0/events/in_illuminance_thresh_either_en
1
akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ i2cget -f -y 1 0x53 0x19
0x14
akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ echo 0x19 | sudo tee direct_reg_access 
0x19
akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ cat direct_reg_access
0x14

5. Write falling threshold via debugfs, verify the threshold written via sysfs.
akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ echo 0x24 0x32 | sudo tee direct_reg_access 
0x24 0x32
akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ cat direct_reg_access
0x32
akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ echo 0x25 0x0 | sudo tee direct_reg_access 
0x25 0x0
akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ cat direct_reg_access
0x0
akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ echo 0x26 0x0 | sudo tee direct_reg_access 
0x26 0x0
akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ cat direct_reg_access
0x0
akshayajpi@raspberrypi:/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:         63          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@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ echo 0xd 0x1 | sudo tee direct_reg_access
0xd 0x1
tee: direct_reg_access: Input/output error
akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ echo 0xe 0x1 | sudo tee direct_reg_access
0xe 0x1
tee: direct_reg_access: Input/output error
akshayajpi@raspberrypi:/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@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ echo 0x2 |sudo tee direct_reg_access 
0x2
akshayajpi@raspberrypi:/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@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ cat /sys/bus/iio/devices/iio\:device0/in_illuminance_raw
627
akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ cat /sys/bus/iio/devices/iio\:device0/in_illuminance_raw
622
akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ cat /sys/bus/iio/devices/iio\:device0/in_illuminance_raw
616

-> reading via debugfs (should be in the same ballpark of sysfs)
akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ echo 0xd | sudo tee direct_reg_access
0xd
akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ cat direct_reg_access 
0xC7
akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ echo 0xe | sudo tee direct_reg_access
0xe
akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ cat direct_reg_access 
0x2
akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ echo 0xf | sudo tee direct_reg_access
0xf
akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ cat direct_reg_access 
0x0
final value = 0x0 << 16 | 0x2 << 8 | 0x70 = 624

10. Testing reads on registers beyond max_register.
akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ echo 0x27 | sudo tee direct_reg_access 
0x27
akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ cat direct_reg_access 
cat: direct_reg_access: Input/output error
akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ echo 0x28 | sudo tee direct_reg_access 
0x28
akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ cat direct_reg_access 
cat: direct_reg_access: Input/output error

 drivers/iio/light/ltr390.c | 55 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 55 insertions(+)

diff --git a/drivers/iio/light/ltr390.c b/drivers/iio/light/ltr390.c
index ee59bbb8aa09..b63301648689 100644
--- a/drivers/iio/light/ltr390.c
+++ b/drivers/iio/light/ltr390.c
@@ -38,12 +38,21 @@
 #define LTR390_ALS_UVS_GAIN		0x05
 #define LTR390_PART_ID			0x06
 #define LTR390_MAIN_STATUS		0x07
+
 #define LTR390_ALS_DATA			0x0D
+#define LTR390_ALS_DATA_BYTE(n)		((LTR390_ALS_DATA) + (n))
+
 #define LTR390_UVS_DATA			0x10
+#define LTR390_UVS_DATA_BYTE(n)		((LTR390_UVS_DATA) + (n))
+
 #define LTR390_INT_CFG			0x19
 #define LTR390_INT_PST			0x1A
+
 #define LTR390_THRESH_UP		0x21
+#define LTR390_THRESH_UP_BYTE(n)	((LTR390_THRESH_UP) + (n))
+
 #define LTR390_THRESH_LOW		0x24
+#define LTR390_THRESH_LOW_BYTE(n)	((LTR390_THRESH_LOW) + (n))
 
 #define LTR390_PART_NUMBER_ID		0xb
 #define LTR390_ALS_UVS_GAIN_MASK	GENMASK(2, 0)
@@ -98,11 +107,42 @@ struct ltr390_data {
 	int int_time_us;
 };
 
+static const struct regmap_range ltr390_readable_reg_ranges[] = {
+	regmap_reg_range(LTR390_MAIN_CTRL, LTR390_MAIN_CTRL),
+	regmap_reg_range(LTR390_ALS_UVS_MEAS_RATE, LTR390_MAIN_STATUS),
+	regmap_reg_range(LTR390_ALS_DATA_BYTE(0), LTR390_ALS_DATA_BYTE(2)),
+	regmap_reg_range(LTR390_UVS_DATA_BYTE(0), LTR390_UVS_DATA_BYTE(2)),
+	regmap_reg_range(LTR390_INT_CFG, LTR390_INT_PST),
+	regmap_reg_range(LTR390_THRESH_UP_BYTE(0), LTR390_THRESH_UP_BYTE(2)),
+	regmap_reg_range(LTR390_THRESH_LOW_BYTE(0), LTR390_THRESH_LOW_BYTE(2)),
+};
+
+static const struct regmap_access_table ltr390_readable_reg_table = {
+	.yes_ranges = ltr390_readable_reg_ranges,
+	.n_yes_ranges = ARRAY_SIZE(ltr390_readable_reg_ranges),
+};
+
+static const struct regmap_range ltr390_writeable_reg_ranges[] = {
+	regmap_reg_range(LTR390_MAIN_CTRL, LTR390_MAIN_CTRL),
+	regmap_reg_range(LTR390_ALS_UVS_MEAS_RATE, LTR390_ALS_UVS_GAIN),
+	regmap_reg_range(LTR390_INT_CFG, LTR390_INT_PST),
+	regmap_reg_range(LTR390_THRESH_UP_BYTE(0), LTR390_THRESH_UP_BYTE(2)),
+	regmap_reg_range(LTR390_THRESH_LOW_BYTE(0), LTR390_THRESH_LOW_BYTE(2)),
+};
+
+static const struct regmap_access_table ltr390_writeable_reg_table = {
+	.yes_ranges = ltr390_writeable_reg_ranges,
+	.n_yes_ranges = ARRAY_SIZE(ltr390_writeable_reg_ranges),
+};
+
 static const struct regmap_config ltr390_regmap_config = {
 	.name = "ltr390",
 	.reg_bits = 8,
 	.reg_stride = 1,
 	.val_bits = 8,
+	.max_register = LTR390_THRESH_LOW_BYTE(2),
+	.rd_table = &ltr390_readable_reg_table,
+	.wr_table = &ltr390_writeable_reg_table,
 };
 
 /* Sampling frequency is in mili Hz and mili Seconds */
@@ -586,6 +626,20 @@ 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)
+{
+	struct ltr390_data *data = iio_priv(indio_dev);
+
+	guard(mutex)(&data->lock);
+
+	if (readval)
+		return regmap_read(data->regmap, reg, readval);
+
+	return regmap_write(data->regmap, reg, writeval);
+}
+
 static const struct iio_info ltr390_info = {
 	.read_raw = ltr390_read_raw,
 	.write_raw = ltr390_write_raw,
@@ -594,6 +648,7 @@ 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
Re: [PATCH v2] iio: light: ltr390: Add debugfs register access support
Posted by David Lechner 4 months, 4 weeks ago 
On 7/23/25 1:04 PM, Akshay Jindal wrote:
> 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@gmail.com>
> ---
> 
> Changes since v1:
> =================
> - Replaced _[0|1|2] macros with a respective common parameterized macro.
> - Retained base macros to avoid churn.
> - Swapped regmap_write with regmap_read to avoid negate operator.
> - Simplified debugfs function by directly returning return value of
>   regmap_[read|write].
> - Replaced [readable|writeable]_reg with regmap ranges by using
>   [rd|wr]_table property of regmap_config.
>  
> Testing details(updated):
> ========================
> -> Tested on Raspberrypi 4B. Follow for more details.
> 
> akshayajpi@raspberrypi:~ $ uname -r
> 6.12.35-v8+
> akshayajpi@raspberrypi:~ $ 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@raspberrypi:~ $ 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@raspberrypi:~ $ sudo dtoverlay i2c-sensor ltr390
> akshayajpi@raspberrypi:~ $ 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@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ echo 0x0 | sudo tee direct_reg_access
> 0x0
> akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ cat direct_reg_access
> 0x2
> akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ echo 0x0 0x0 | sudo tee direct_reg_access
> 0x0 0x0
> akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ cat direct_reg_access
> 0x0
> akshayajpi@raspberrypi:/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@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ cat /sys/bus/iio/devices/iio\:device0/in_illuminance_raw
> 603
> akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ cat /sys/bus/iio/devices/iio\:device0/in_illuminance_raw
> 603
> akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ cat /sys/bus/iio/devices/iio\:device0/in_illuminance_raw
> 603
> akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ i2cget -f -y 1 0x53 0x7
> 0x28
> akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ i2cget -f -y 1 0x53 0x7
> 0x00
> akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ echo 0x7 | sudo tee direct_reg_access
> 0x7
> akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ cat direct_reg_access
> 0x0
> 
> 3. Re-enable sensor via debugfs and read data status via debugfs.
> akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ echo 0x0 0x2 | sudo tee direct_reg_access
> 0x0 0x2
> akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ cat direct_reg_access
> 0x2
> akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ cat /sys/bus/iio/devices/iio\:device0/in_illuminance_raw
> 608
> akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ cat /sys/bus/iio/devices/iio\:device0/in_illuminance_raw
> 614
> akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ cat /sys/bus/iio/devices/iio\:device0/in_illuminance_raw
> 601
> akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ echo 0x7 | sudo tee direct_reg_access
> 0x7
> akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ cat direct_reg_access
> 0x8
> 
> 4. Enable interrupts via sysfs and verify via debugfs.
> akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ echo 1 | sudo tee /sys/bus/iio/devices/iio\:device0/events/in_illuminance_thresh_either_en
> 1
> akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ i2cget -f -y 1 0x53 0x19
> 0x14
> akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ echo 0x19 | sudo tee direct_reg_access 
> 0x19
> akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ cat direct_reg_access
> 0x14
> 
> 5. Write falling threshold via debugfs, verify the threshold written via sysfs.
> akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ echo 0x24 0x32 | sudo tee direct_reg_access 
> 0x24 0x32
> akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ cat direct_reg_access
> 0x32
> akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ echo 0x25 0x0 | sudo tee direct_reg_access 
> 0x25 0x0
> akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ cat direct_reg_access
> 0x0
> akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ echo 0x26 0x0 | sudo tee direct_reg_access 
> 0x26 0x0
> akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ cat direct_reg_access
> 0x0
> akshayajpi@raspberrypi:/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:         63          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@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ echo 0xd 0x1 | sudo tee direct_reg_access
> 0xd 0x1
> tee: direct_reg_access: Input/output error
> akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ echo 0xe 0x1 | sudo tee direct_reg_access
> 0xe 0x1
> tee: direct_reg_access: Input/output error
> akshayajpi@raspberrypi:/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@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ echo 0x2 |sudo tee direct_reg_access 
> 0x2
> akshayajpi@raspberrypi:/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@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ cat /sys/bus/iio/devices/iio\:device0/in_illuminance_raw
> 627
> akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ cat /sys/bus/iio/devices/iio\:device0/in_illuminance_raw
> 622
> akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ cat /sys/bus/iio/devices/iio\:device0/in_illuminance_raw
> 616
> 
> -> reading via debugfs (should be in the same ballpark of sysfs)
> akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ echo 0xd | sudo tee direct_reg_access
> 0xd
> akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ cat direct_reg_access 
> 0xC7
> akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ echo 0xe | sudo tee direct_reg_access
> 0xe
> akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ cat direct_reg_access 
> 0x2
> akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ echo 0xf | sudo tee direct_reg_access
> 0xf
> akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ cat direct_reg_access 
> 0x0
> final value = 0x0 << 16 | 0x2 << 8 | 0x70 = 624
> 
> 10. Testing reads on registers beyond max_register.
> akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ echo 0x27 | sudo tee direct_reg_access 
> 0x27
> akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ cat direct_reg_access 
> cat: direct_reg_access: Input/output error
> akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ echo 0x28 | sudo tee direct_reg_access 
> 0x28
> akshayajpi@raspberrypi:/sys/kernel/debug/iio/iio:device0 $ cat direct_reg_access 
> cat: direct_reg_access: Input/output error
> 
>  drivers/iio/light/ltr390.c | 55 ++++++++++++++++++++++++++++++++++++++
>  1 file changed, 55 insertions(+)
> 
> diff --git a/drivers/iio/light/ltr390.c b/drivers/iio/light/ltr390.c
> index ee59bbb8aa09..b63301648689 100644
> --- a/drivers/iio/light/ltr390.c
> +++ b/drivers/iio/light/ltr390.c
> @@ -38,12 +38,21 @@
>  #define LTR390_ALS_UVS_GAIN		0x05
>  #define LTR390_PART_ID			0x06
>  #define LTR390_MAIN_STATUS		0x07
> +
>  #define LTR390_ALS_DATA			0x0D
> +#define LTR390_ALS_DATA_BYTE(n)		((LTR390_ALS_DATA) + (n))
> +
>  #define LTR390_UVS_DATA			0x10
> +#define LTR390_UVS_DATA_BYTE(n)		((LTR390_UVS_DATA) + (n))
> +
>  #define LTR390_INT_CFG			0x19
>  #define LTR390_INT_PST			0x1A
> +
>  #define LTR390_THRESH_UP		0x21
> +#define LTR390_THRESH_UP_BYTE(n)	((LTR390_THRESH_UP) + (n))
> +
>  #define LTR390_THRESH_LOW		0x24
> +#define LTR390_THRESH_LOW_BYTE(n)	((LTR390_THRESH_LOW) + (n))
>  
>  #define LTR390_PART_NUMBER_ID		0xb
>  #define LTR390_ALS_UVS_GAIN_MASK	GENMASK(2, 0)
> @@ -98,11 +107,42 @@ struct ltr390_data {
>  	int int_time_us;
>  };
>  
> +static const struct regmap_range ltr390_readable_reg_ranges[] = {
> +	regmap_reg_range(LTR390_MAIN_CTRL, LTR390_MAIN_CTRL),
> +	regmap_reg_range(LTR390_ALS_UVS_MEAS_RATE, LTR390_MAIN_STATUS),
> +	regmap_reg_range(LTR390_ALS_DATA_BYTE(0), LTR390_ALS_DATA_BYTE(2)),
> +	regmap_reg_range(LTR390_UVS_DATA_BYTE(0), LTR390_UVS_DATA_BYTE(2)),
> +	regmap_reg_range(LTR390_INT_CFG, LTR390_INT_PST),
> +	regmap_reg_range(LTR390_THRESH_UP_BYTE(0), LTR390_THRESH_UP_BYTE(2)),
> +	regmap_reg_range(LTR390_THRESH_LOW_BYTE(0), LTR390_THRESH_LOW_BYTE(2)),


We don't need separate lines if there is no gap. I didn't check all of the lines
but at least these last two can be combined since LTR390_THRESH_UP_BYTE(2) is
0x23 and LTR390_THRESH_LOW_BYTE(0) is 0x24.

	regmap_reg_range(LTR390_THRESH_UP, LTR390_THRESH_LOW + 2),

And we could avoid adding the extra macros just for this since they
aren't used anywhere else.

> +};
> +
Re: [PATCH v2] iio: light: ltr390: Add debugfs register access support
Posted by Akshay Jindal 4 months, 3 weeks ago 
On Thu, Jul 24, 2025 at 1:44 AM David Lechner <dlechner@baylibre.com> wrote:
> We don't need separate lines if there is no gap. I didn't check all of the lines
> but at least these last two can be combined since LTR390_THRESH_UP_BYTE(2) is
> 0x23 and LTR390_THRESH_LOW_BYTE(0) is 0x24.
Done. In other lines there is no gap.
For your convenience, I am writing the actual value of these macros as comments.
static const struct regmap_range ltr390_readable_reg_ranges[] = {
       regmap_reg_range(LTR390_MAIN_CTRL, LTR390_MAIN_CTRL), // (0x0-->0x0)
       regmap_reg_range(LTR390_ALS_UVS_MEAS_RATE,
LTR390_MAIN_STATUS),//(0x4-->0x7)
       regmap_reg_range(LTR390_ALS_DATA_BYTE(0),
LTR390_ALS_DATA_BYTE(2)),//(0xd-->0xf)
       regmap_reg_range(LTR390_UVS_DATA_BYTE(0),
LTR390_UVS_DATA_BYTE(2)),//(0x10-->0x12)
       regmap_reg_range(LTR390_INT_CFG, LTR390_INT_PST),//(0x19-->0x1A)
       regmap_reg_range(LTR390_THRESH_UP_BYTE(0),
LTR390_THRESH_LOW_BYTE(2)),//(0x21-->0x26)
};

>
> And we could avoid adding the extra macros just for this since they
> aren't used anywhere else.
>
I only added the following macros:
+#define LTR390_ALS_DATA_BYTE(n)                ((LTR390_ALS_DATA) + (n))
+#define LTR390_UVS_DATA_BYTE(n)               ((LTR390_UVS_DATA) + (n))
+#define LTR390_THRESH_UP_BYTE(n)            ((LTR390_THRESH_UP) + (n))
+#define LTR390_THRESH_LOW_BYTE(n)         ((LTR390_THRESH_LOW) + (n))

I can remove them too, but then in regmap_range, I will have to
statically write like you mentioned.
regmap_reg_range(LTR390_THRESH_UP, LTR390_THRESH_LOW + 2).
That is also fine, but I feel that using parameterized macros is a
much cleaner way, as also mentioned
in v1 review comments by other maintainers. Let me know your thoughts.
I am happy to let them go too.

Thanks,
Akshay

Patchew 2.1-devel-b67e4c2

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