sensors: probing a streaming SP2305 no longer turns its picture white

[openipc-ai]

What happened

On HiSilicon the GalaxyCore probe runs at 0x78, the same 7-bit address as the SuperPix probe's 0x79, which is an SP2305 / OV2735. The GalaxyCore probe's first read used a two-byte register address, 0x3f0.

The SP2305 has one-byte addresses, so it took that read as a write: 0xf0, then 0xf1, into register 0x03. That is the high byte of its exposure.

On a camera that was streaming, the picture went white and stayed white until the streamer restarted. The sensor driver rewrites the exposure only when it changes, and in a bright scene it doesn't (OpenIPC/openhisilicon#255 fixes that side). ipctool -s and ipcinfo --short-sensor both did it, every time. This is very likely the random white-out in OpenIPC/majestic#295.

Changes

• SuperPix probed before GalaxyCore. It only reads and writes one byte of address at a time, so a part in that register family is named before any two-byte address reaches it.
• GalaxyCore tries the byte-address ID first (0xf0/0xf1) and only falls back to the two-byte one for an ID that doesn't name a part. The GC1004 that 0x78 was added for has one-byte addresses, and its exposure is at 0x03 too.
• SuperPix page select fixed. It now selects page 0 with one data byte, not two (the second went on into 0xFE), and puts back the page it found. A streamer writes the exposure to page 1 without reselecting the page every time.

Tests

• Fingerprint: src/sensors_golden.txt is unchanged; every ID names the same part as before.
• New check in sensors_test: a scripted SP2305 on page 1, at an address shared with a GalaxyCore probe.
  • Against the old code it records two two-byte reads, a two-byte page write, and page 0 left selected.
  • Against this change it records none of them.
• Other suites: all host tests in pr-build-check.yml pass.

On hardware

hi3516ev300 + SP2305/OV2735, streaming under an LED floodlight, auto-exposure at ~130 lines:

	before	after
ipctool -s	"unexpected value for GalaxyCore", then picture white, register 0x03 = 0xf1	ov2735_i2c, register and picture unchanged
ipcinfo --short-sensor	picture white	ov2735, unchanged
full ipctool report	—	OmniVision OV2735 at 0x79, unchanged

[qodo-free-for-open-source-projects]

PR Summary by Qodo

Prevent sensor probing from whitening a streaming SP2305

🐞 Bug fix 🧪 Tests 🕐 10-20 Minutes

AI Description

• Probe SuperPix before GalaxyCore to identify shared-address sensors without hazardous two-byte
 reads.
• Preserve the sensor’s register page and use one-byte page writes during SuperPix detection.
• Add a streaming-SP2305 regression test while retaining the existing sensor-ID fingerprint.

Diagram

graph TD
  Scan["I²C sensor scan"] --> SuperPix["SuperPix probe"] --> PageID["Page-zero ID"] --> Restore["Restore page"] --> GalaxyCore["GalaxyCore probe"] --> Narrow["Byte-address ID"] --> Wide["Two-byte fallback"]
  Restore -- "matched" --> Identified["Sensor identified"]
  Restore -- "no match" --> GalaxyCore
  Narrow -- "matched" --> Identified
  Wide -- "matched" --> Identified

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High-Level Assessment

The following are alternative approaches to this PR:

1. Gate two-byte reads by sensor address metadata

• ➕ Could prevent two-byte transactions at every address known to host one-byte-register sensors.
• ➖ Requires reliable platform-specific address and register-width data.
• ➖ Risks suppressing detection of GalaxyCore parts that need the two-byte ID path.

Recommendation: The targeted probe order and byte-first identification are appropriate because they protect the reported shared-address sensor while preserving existing GalaxyCore identification paths. Address-based gating is worth considering only if further collisions show the remaining two-byte fallback needs broader safeguards.

Files changed (2) +150 / -45

Bug fix (1) +66 / -45

sensors.cMake shared-address detection safer for streaming sensors +66/-45

Make shared-address detection safer for streaming sensors

• Moves SuperPix ahead of GalaxyCore and tries GalaxyCore byte-address IDs before two-byte IDs. SuperPix detection now uses one-byte page-select writes and restores the original page after reading the ID.

src/sensors.c

Tests (1) +84 / -0

sensors_test.cCover a streaming SP2305 at a shared probe address +84/-0

Cover a streaming SP2305 at a shared probe address

• Adds a scripted page-1 SP2305/OV2735 to the full sensor scan. The test checks its identification, absence of two-byte transactions or malformed page writes, and restoration of page 1.

src/sensors_test.c

[qodo-free-for-open-source-projects]

Code Review by Qodo

🐞 Bugs (0) 📘 Rule violations (0) 📎 Requirement gaps (0)

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