On 22/03/21 13:11, Greg KH wrote:
XILLYBUS and XILLYBUS_PCIE are currently enabled as M in several Linux
distributions. Making them depend on, rather than select XILLYBUS_CLASS is
likely to disable the driver in those distributions.
That's not an issue here, depends-on will allow those distros to also
enable this option.
But wait, why is this a separate option at all? Shouldn't the class
code just be part of the "core" XILLYBUS code anyway?
I'll try to explain the whole picture:
XILLYBUS_CLASS
/ \
| |
XILLYBUS XILLYUSB
/ \
| |
XILLYBUS_PCIE XILLYBUS_OF
XILLYBUS_CLASS is new and common to all drivers in this group.
XILLYBUS is for drivers based upon memory registers + DMA-based
interfaces, and it's combined with XILLYBUS_PCIE and/or XILLYBUS_OF.
XILLYUSB is for the USB variant only.
Or a more detailed, bottom-up outline:
* CONFIG_XILLYBUS_PCIE -> xillybus_pcie.c: Functions related to PCIe.
* CONFIG_XILLYBUS_OF -> xillybus_of.c: Functions related to Xillybus as
a peripheral on an FPGA / Processor combo chip.
* CONFIG_XILLYBUS -> xillybus_core.c: Functions that are common to the
two above, mainly access to the peripheral with memory-mapped registers
and DMA.
* CONFIG_XILLYUSB -> xillyusb.c: The driver for the USB variant,
accesses the peripheral through the USB framework.
* CONFIG_XILLYBUS_CLASS -> xillybus_class.c: The new module, which
contains the class and API parts that would otherwise appear both in
xillybus_core.c and xillyusb.c. Contains utility functions for the two
latter.
Because XILLYBUS_CLASS is new and "N" by default, making a "depends on"
relationship means that "make olddefconfig" silently turns off
CONFIG_XILLYBUS and CONFIG_XILLYBUS_PCIE. That's a bug: Adding a new
driver shouldn't change anything in the existing configuration.
That's why I had the "select XILLYBUS_CLASS" to begin with: It ensures a
smooth transition on a kernel upgrade, by adding XILLYBUS_CLASS to
kernels that had CONFIG_XILLYBUS enabled. Is there another way to
prevent the said bug, without "select"?
Thanks and regards,
Eli
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