While the flag bytes in Flash on the PS175 indicate which partition it is
desired the device boot, the device may actually boot something else
because it performs some kind of integrity check on firmware images before
booting them. If the image specified by the flag bytes fails validation,
the device instead boots partition 3 which should be treated as read-only.
The device provides a register on I2C that indicates which partition is
actually running, so probe that register rather than assuming the device
is running the image that the flag bytes specify.
Signed-off-by: Peter Marheine <pmarheine@chromium.org>
Having a mutable global flash layout makes it difficult to reason about which
flash regions will be affected by any given flashrom operation. Make copies of
the layout from a template instead, and default-exclude regions from
operations.
sysfs paths don't have strong guarantees about semantics, so attempting
to parse an I2C bus number out of a sysfs path of some device is likely
to be fragile. Instead take advantage of the device layout to find the
I2C bus an LSPCON is on without trying to parse it out of paths.
The bus the device is on is a sibling device of type i2c-dev, so by
locating an i2c-dev device that is a sibling of the detected LSPCON
device, the /dev path of the bus can be found robustly.
Support for specifying an I2C bus by path rather than number is also
required in flashrom, implemented at
https://review.coreboot.org/c/flashrom/+/51967
Signed-off-by: Peter Marheine <pmarheine@chromium.org>
Created lspcon-i2c-spi flashrom device that uses udev to detect i2c
devices that can be updated with the lspcon-i2c-spi flashrom programmer.
This change implements the logic from crrev.com/c/2792124 adapted to the
upstream flashrom plugin.
