Documentation/driver-api/gpio/pca953x.rst
Source file repositories/reference/linux-study-clean/Documentation/driver-api/gpio/pca953x.rst
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Documentation/driver-api/gpio/pca953x.rst- Extension
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Why This File Exists
Repository support layer: documentation, build tooling, samples, user-space helper tools, generated initramfs support, licenses, and validation utilities.
- Repository support layer: documentation, build tooling, samples, user-space helper tools, generated initramfs support, licenses, and validation utilities.
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Annotated Snippet
============================================
PCA953x I²C GPIO expander compatibility list
============================================
:Author: Levente Révész <levente.revesz@eilabs.com>
I went through all the datasheets and created this note listing
chip functions and register layouts.
Overview of chips
=================
Chips with the basic 4 registers
--------------------------------
These chips have 4 register banks: input, output, invert and direction.
Each of these banks contains (lines/8) registers, one for each GPIO port.
Banks offset is always a power of 2:
- 4 lines -> bank offset is 1
- 8 lines -> bank offset is 1
- 16 lines -> bank offset is 2
- 24 lines -> bank offset is 4
- 32 lines -> bank offset is 4
- 40 lines -> bank offset is 8
For example, register layout of GPIO expander with 24 lines:
+------+-----------------+--------+
| addr | function | bank |
+======+=================+========+
| 00 | input port0 | |
+------+-----------------+ |
| 01 | input port1 | bank 0 |
+------+-----------------+ |
| 02 | input port2 | |
+------+-----------------+--------+
| 03 | n/a | |
+------+-----------------+--------+
| 04 | output port0 | |
+------+-----------------+ |
| 05 | output port1 | bank 1 |
+------+-----------------+ |
| 06 | output port2 | |
+------+-----------------+--------+
| 07 | n/a | |
+------+-----------------+--------+
| 08 | invert port0 | |
+------+-----------------+ |
| 09 | invert port1 | bank 2 |
+------+-----------------+ |
| 0A | invert port2 | |
+------+-----------------+--------+
| 0B | n/a | |
+------+-----------------+--------+
| 0C | direction port0 | |
+------+-----------------+ |
| 0D | direction port1 | bank 3 |
+------+-----------------+ |
| 0E | direction port2 | |
+------+-----------------+--------+
| 0F | n/a | |
+------+-----------------+--------+
.. note::
This is followed by all supported chips, except by pcal6534.
The table below shows the offsets for each of the compatible chips:Annotation
- Atlas domain: Support Tooling And Documentation / Documentation.
- Implementation status: atlas-only.
Implementation Notes
- This generated page is the file-by-file coverage layer; curated subsystem chapters should link here when they synthesize a multi-file control flow.
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