Hi,
A relatively recent patch [1] to the spi-bcm2835 driver modified it to
use GPIO descriptors for chip select handling. A side effect of this
change is to set the SPI_MODE_CS_HIGH flag for devices connected to the
controller, which seems strange since it happens for devices that
require the usual active-low chip select.
This change came to light when a user reported that the SPI-Py library
(a client of the spidev driver) wasn't working on 5.4, which was traced
to it overwriting the SPI mode flags when it was only trying to set the
CPHA and CPOL flags. This had the affect of inverting the chip select
line, with the obvious consequences. That corruption of the flags is
clearly an error, but what if the application and library were genuinely
trying to specify that the attached device required an active-high chip
select? Would it now require that they _clear_ the CS_HIGH flag?
Thanks,
Phil
[1] 3bd158c56a56 ("spi: bcm2835: Convert to use CS GPIO descriptors")
