[RFC,v2,0/2] fpga: improve protection against low-level modules unloading

Message

Marco Pagani Nov. 24, 2023, 4:28 p.m. UTC

This RFC proposes a possible solution to keep protecting the fpga
manager against the sudden unloading of low-level control modules while
addressing the limitations of the current implementation. Currently, the
code assumes that the low-level module registers a platform driver for
the parent device, which can later be used by the fpga manager (through
the parent device pointer) to take the low-level module's refcount. This
proposal removes this limitation by adding a module owner field to the
fpga_manager and fpga_manager_ops structs. Low-level control modules can
statically set the owner field to THIS_MODULE. Later, the fpga manager
can use the owner field to take the module's refcount.

For more context, please refer to these threads:
https://lore.kernel.org/linux-fpga/ZS6hhlvjUcqyv8zL@yilunxu-OptiPlex-7050
https://lore.kernel.org/linux-fpga/ZT9qENE9fE3Z0KCW@yilunxu-OptiPlex-7050

v2:
- Fixed protection against races during module removal

Marco Pagani (2):
  fpga: add a module owner field to fpga_manager and fpga_manager_ops
  fpga: set owner of fpga_manager_ops for existing low-level modules

 drivers/fpga/altera-cvp.c             |  1 +
 drivers/fpga/altera-pr-ip-core.c      |  1 +
 drivers/fpga/altera-ps-spi.c          |  1 +
 drivers/fpga/dfl-fme-mgr.c            |  1 +
 drivers/fpga/fpga-mgr.c               | 56 +++++++++++++++++++--------
 drivers/fpga/ice40-spi.c              |  1 +
 drivers/fpga/lattice-sysconfig.c      |  1 +
 drivers/fpga/machxo2-spi.c            |  1 +
 drivers/fpga/microchip-spi.c          |  1 +
 drivers/fpga/socfpga-a10.c            |  1 +
 drivers/fpga/socfpga.c                |  1 +
 drivers/fpga/stratix10-soc.c          |  1 +
 drivers/fpga/tests/fpga-mgr-test.c    |  1 +
 drivers/fpga/tests/fpga-region-test.c |  1 +
 drivers/fpga/ts73xx-fpga.c            |  1 +
 drivers/fpga/versal-fpga.c            |  1 +
 drivers/fpga/xilinx-spi.c             |  1 +
 drivers/fpga/zynq-fpga.c              |  1 +
 drivers/fpga/zynqmp-fpga.c            |  1 +
 include/linux/fpga/fpga-mgr.h         |  4 ++
 20 files changed, 62 insertions(+), 16 deletions(-)


base-commit: 98b1cc82c4affc16f5598d4fa14b1858671b2263