MCP23S17 bias pull-up not working
Nobody has claimed this yet.
Assessment
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Newbie friendliness
- 42/100
- Issue type
- Bug
- Clarity
- Mostly clear
- Activity status
- Stale
- Tech stack
- c, linux
- Domain
- embedded-iot, operating-systems
Research direction
Start by reproducing the issue with gpioget --bias=pull-up gpiochip2 0 on an MCP23S17 using dtoverlay=mcp23s17, then inspect the pinctrl-mcp23s08 driver’s pull-up handling. Compare the command result with the GPPUA register value; done means the pull-up is enabled and pin 0 reports the expected value.
Written by the indexing model from the issue text.
Description
Describe the bug
pinctrl-mcp23s08 driver unable to enable pull-up resister on MCP23S17(dtoverlay=mcp23s17)
Steps to reproduce the behaviour
using the following command to read pin 0 on gpiochip2 (MCP23S17 on SPI0.0)
gpioget --bias=pull-up gpiochip2 0
# got 0, expect 1
Device (s)
Raspberry Pi 4 Mod. B
System
Linux dev 6.12.20+rpt-rpi-v8 #1 SMP PREEMPT Debian 1:6.12.20-1+rpt1~bpo12+1 (2025-03-19) aarch64 GNU/Linux
Logs
No response
Additional context
reading GPPUA directly from device return 0b00000000, which indicate that pull-up is not enabled
- Dominant language
- C
- Stars
- 13.2k
- Forks
- 5.5k
- Avg merge
- 2d 21h
- Merged PRs (30d)
- 21
Contributor guide
No contributing guide indexed for this repository
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
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