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From:   Marco Pagani <marpagan@redhat.com>
To:     Moritz Fischer <mdf@kernel.org>, Wu Hao <hao.wu@intel.com>,
        Xu Yilun <yilun.xu@intel.com>, Tom Rix <trix@redhat.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc:     Marco Pagani <marpagan@redhat.com>, linux-kernel@vger.kernel.org,
        linux-fpga@vger.kernel.org
Subject: [RFC PATCH 0/2] fpga: improve protection against low-level modules unloading
Date:   Wed, 22 Nov 2023 15:32:50 +0100
Message-ID: <20231122143252.181680-1-marpagan@redhat.com>
MIME-Version: 1.0
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Precedence: bulk

This RFC proposes a possible solution to keep protecting the fpga
manager against the unexpected unloading of low-level control modules
while addressing the limitations of the current implementation. The
current implementation 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

Signed-off-by: Marco Pagani <marpagan@redhat.com>

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
-- 
2.42.0