[PATCH v3 0/3] Samsung Expressatt: Camera Flash

Rudraksha Gupta via B4 Relay
2026-03-26T07:57:32Z

This small series adds camera flash to an existing similar mainline
driver and adds it to the Samsung Expressatt's DTS

// Tests

// # Navigate to LED
sudo su
cd /sys/class/leds/white:flash

// # Should stay at dim brightness
echo 1 > brightness
echo 1 > brightness
echo 1 > brightness
echo 1 > brightness
echo 0 > brightness # LED_OFF

// # Max Brightness
echo 50 > brightness
echo 0 > brightness # LED_OFF
echo 99 > brightness
echo 0 > brightness # LED_OFF
echo 1000 > brightness
echo 0 > brightness # LED_OFF
echo 100 > brightness
echo 0 > brightness # LED_OFF

// # Should increase in brightness
for i in $(seq 1 16); do echo $i > brightness; sleep 1; done
echo 0 > brightness # LED_OFF

// # Test flash strobe (rt8515_led_flash_strobe_set)
cat max_flash_timeout # check max
echo 200000 > flash_timeout # 200ms
echo 1 > flash_strobe # strobe ON → brightness_commit + timer
cat flash_strobe # should read 1, then 0 after timeout
sleep 1
cat flash_strobe # should be 0 (timer fired)

// # Test manual strobe cancel
echo 1 > flash_strobe ; echo 0 > flash_strobe # immediate off

// # Check regulator error handling
dmesg | tail -20 # look for any "failed to turn off LED" msgs

Downstream reference:
Link: https://github.com/LineageOS/android_kernel_samsung_d2/blob/stable/cm-12.0-YNG4N/drivers/leds/Makefile#L51
Link: https://github.com/LineageOS/android_kernel_samsung_d2/blob/stable/cm-12.0-YNG4N/arch/arm/mach-msm/board-apexq-camera.c#L591

Signed-off-by: Rudraksha Gupta <guptarud@gmail.com>
---
Changes in v3:
- DTS:
- Renamed and reordered nodes
- Driver:
- Use regulator_is_enabled() instead of reg_enabled
- remove ent xor vin check
- remove rt->reg == -ENODEV check
- rename functions to reflect what they do and added ret's
- Fixed: LED was increasing in brightness when setting the same
brightness multiple times
- Link to v2: https://lore.kernel.org/r/20260318-expressatt_camera_flash-v2-0-5c2b9a623dcb@gmail.com

Changes in v2:
- dt-bindings: Explain the hardware and not the driver
- **/*: Use vin-supply instead of unlock-gpio
- expressatt DTS: Reorder pinctrl-*
- expressatt DTS: Define rfs-ohms to a default (couldn't find
information about this)
- Link to v1: https://lore.kernel.org/r/20260306-expressatt_camera_flash-v1-0-b1996f7cdfdd@gmail.com

---
Rudraksha Gupta (3):
dt-bindings: leds: rt8515: Support single-GPIO flash ICs with vin supply
leds: flash: rt8515: Support single-GPIO flash ICs with vin supply
ARM: dts: qcom: msm8960: expressatt: Add camera flash

.../devicetree/bindings/leds/richtek,rt8515.yaml | 34 +++++++-
.../dts/qcom/qcom-msm8960-samsung-expressatt.dts | 43 +++++++++++
drivers/leds/flash/leds-rt8515.c | 90 +++++++++++++++++-----
3 files changed, 148 insertions(+), 19 deletions(-)
---
base-commit: e9ec05addd1a067fc7cb218f20ecdc1b1b0898c0
change-id: 20260306-expressatt_camera_flash-13c15a7427aa
prerequisite-message-id: <20251205-expressatt-touchkey-v1-1-1444b927c9f3@gmail.com>
prerequisite-patch-id: 8de4de7909722ccaf385c4224f25a623eaa72c28

Best regards,
--
Rudraksha Gupta <guptarud@gmail.com>