Accessing GPIOs over pin 26 causes an exception on a Pi 4B

[Juerg Haefliger]

[Impact]

With Focal running on a Pi 4B accessing any GPIO over 26 causes an exception:

$ python3
Python 3.8.5 (default, Jul 28 2020, 12:59:40)
[GCC 9.3.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import RPi.GPIO as gpio
>>> print(gpio.VERSION)
0.6.5
>>> gpio.setmode(gpio.BOARD)
>>> gpio.setup(22, gpio.IN)
>>> gpio.setup(24, gpio.IN)
>>> gpio.setup(26, gpio.IN)
>>> gpio.setup(32, gpio.IN)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: The channel sent is invalid on a Raspberry Pi

Note that the above works fine on a Pi 3A+. Also, works fine on a Pi 4B after installing python3-rpi.gpio from Groovy:

$ python3
Python 3.8.5 (default, Jul 28 2020, 12:59:40)
[GCC 9.3.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import RPi.GPIO as gpio
>>> gpio.setmode(gpio.BOARD)
>>> print(gpio.VERSION)
0.7.0
>>> gpio.setmode(gpio.BOARD)
>>> gpio.setup(22, gpio.IN)
>>> gpio.setup(24, gpio.IN)
>>> gpio.setup(26, gpio.IN)
>>> gpio.setup(32, gpio.IN)
>>> gpio.setup(36, gpio.IN)
>>> gpio.setup(38, gpio.IN)
>>> gpio.setup(40, gpio.IN)

[Test Case]

See above.

[Fix]

Backport version 0.7.0-0.2 from Groovy to Focal. The changes between Focal's 0.6.5 and Groovy's 0.7.0 are mostly fixes for Pi 4B support so backporting is easier/cleaner than applying individual fixes to 0.6.5.

[Regression Potential]

If this introduces a regression, users would probably see Python exceptions similar to what is shown above.

[Juerg Haefliger (juergh)]

The Pi is not properly detected with 0.6.5:
>>> print(gpio.RPI_INFO)
{'P1_REVISION': 2, 'REVISION': 'b03112', 'TYPE': 'Model B', 'MANUFACTURER': 'Sony', 'PROCESSOR': 'Unknown', 'RAM': 'Unknown'}

Probably needs:
https://sourceforge.net/p/raspberry-gpio-python/code/ci/03be41933c1b4fab3aa0daf2931adb4561029bd1/
https://sourceforge.net/p/raspberry-gpio-python/code/ci/3fe31bd67745a334cd7a33ba441ddf1993208b55/