[PATCH AUTOSEL 6.15 24/35] iio: hid-sensor-prox: Add support for 16-bit report size

From: Zhang Lixu <lixu.zhang@intel.com>

[ Upstream commit ad02ca57e44e9936fca5095840fad9d4b47c5559 ]

On Intel platforms, the HID_USAGE_SENSOR_HUMAN_PROXIMITY report size is 16
bits. This patch adds support for handling 16-bit report sizes for the
HID_USAGE_SENSOR_HUMAN_PROXIMITY usage in the HID sensor proximity driver.

Previously, the driver only supported 8-bit and 32-bit report sizes. With
this change, the driver can now correctly process 16-bit proximity data,
ensuring accurate human presence detection on platforms where this report
size is used.

Signed-off-by: Zhang Lixu <lixu.zhang@intel.com>
Acked-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Link: https://patch.msgid.link/20250317013634.4117399-1-lixu.zhang@intel.com (local)
Signed-off-by: Jonathan Cameron <redacted>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---

Based on my analysis of the commit and the context provided, I'll now
provide my recommendation:

**YES**

## Extensive Analysis

### Code Change Analysis

The commit adds support for 16-bit report sizes in the HID sensor
proximity driver by adding a simple `case 2:` clause to the existing
switch statement in the `prox_capture_sample()` function:

switch (raw_len) {
case 1:
    prox_state->human_presence[chan] = *(u8 *)raw_data * multiplier;
    return 0;
+case 2:
+    prox_state->human_presence[chan] = *(u16 *)raw_data * multiplier;
+    return 0;
case 4:
    prox_state->human_presence[chan] = *(u32 *)raw_data * multiplier;
    return 0;
}

### Why This Should Be Backported

1. **Important Bug Fix**: The commit message clearly states this is
   needed for Intel platforms where `HID_USAGE_SENSOR_HUMAN_PROXIMITY`
   uses 16-bit reports. Without this change, these platforms cannot
   correctly process proximity data, making the sensor completely non-
   functional for 16-bit report sizes.

2. **Minimal Risk and Scope**: The change is extremely small (3 lines
   added) and follows the exact same pattern as existing 8-bit and
   32-bit cases. It's confined to a single function and only affects the
   data parsing path for proximity sensors.

3. **Pattern Consistency**: Looking at the grep results from other IIO
   drivers, handling multiple data sizes (including 16-bit) in switch
   statements is a common pattern throughout the IIO subsystem. This
   change follows established conventions.

4. **Hardware Compatibility**: The commit enables proper functionality
   on Intel platforms that use 16-bit proximity reports. This is a
   hardware compatibility fix rather than a new feature.

5. **No Architectural Changes**: The change doesn't modify any APIs,
   data structures, or architectural components - it simply extends the
   existing data size handling logic.

6. **Similar Successful Backports**: Looking at the reference commits,
   we see that Similar Commit #3 and #4 were both backported (Status:
   YES), and both were fixes for scale/data handling issues in HID
   sensor drivers. This commit follows the same pattern of fixing data
   handling bugs.

7. **Clear Failure Mode**: Without this fix, Intel platforms with 16-bit
   proximity reports would fail to capture proximity data, returning
   `-EINVAL` and making the proximity sensor completely unusable.

8. **Industry-Standard Fix**: The commit comes from Intel (Zhang Lixu)
   with acknowledgment from the HID sensor maintainer (Srinivas
   Pandruvada), indicating this addresses a real hardware compatibility
   issue.

### Risk Assessment

The risk is extremely low because:
- The change only affects the specific case where `raw_len == 2`
- Existing 8-bit and 32-bit handling remains unchanged
- The code follows the exact same pattern as existing cases
- No memory management or complex logic is involved
- Failure would be immediate and obvious (wrong data values)

This commit clearly meets the stable tree criteria: it fixes an
important hardware compatibility bug with minimal risk and no
architectural changes.

 drivers/iio/light/hid-sensor-prox.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/iio/light/hid-sensor-prox.c b/drivers/iio/light/hid-sensor-prox.c
index 4c65b32d34ce4..46f788b0bc3e2 100644
--- a/drivers/iio/light/hid-sensor-prox.c
+++ b/drivers/iio/light/hid-sensor-prox.c

@@ -215,6 +215,9 @@ static int prox_capture_sample(struct hid_sensor_hub_device *hsdev,
 	case 1:
 		prox_state->human_presence[chan] = *(u8 *)raw_data * multiplier;
 		return 0;
+	case 2:
+		prox_state->human_presence[chan] = *(u16 *)raw_data * multiplier;
+		return 0;
 	case 4:
 		prox_state->human_presence[chan] = *(u32 *)raw_data * multiplier;
 		return 0;

-- 
2.39.5