The CS_HIGH handling code triggers a lockup on Raspberry Pi in 5.10 about py-spidev

[fgr1986]

@pelwell Indeed, i can confirm this causes an issue with latest kernels

[fgr1986]

For those looking for a quick kernel rollback, reverting using https://github.com/Hexxeh/rpi-firmware/commits/master
Note that rpi3b was not working with kernel 5.4.83, so it was reverted to 5.4.79

• for rpi3b+: sudo rpi-update 0642816ed05d31fb37fc8fbbba9e1774b475113f
• for rpi4b: sudo rpi-update 453e49bdd87325369b462b40e809d5f3187df21d

[HowardALandman]

There are two bugs here.

1. _spi.cshigh appears True when it actually should be False (SPI standard) by default.
2. Attempting to set it False crashes the program.

So the entirely reasonable-looking code:

if self._spi.cshigh:
    self._spi.cshigh = False

hits both bugs and dies.