[RFC PATCH v5 0/1] fpga: improve protection against low-level control module unloading

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>,
	Jonathan Corbet <corbet@lwn.net>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Alan Tull <atull@opensource.altera.com>
Cc: Marco Pagani <marpagan@redhat.com>,
	linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
	linux-fpga@vger.kernel.org
Subject: [RFC PATCH v5 0/1] fpga: improve protection against low-level control module unloading
Date: Thu, 11 Jan 2024 17:02:41 +0100	[thread overview]
Message-ID: <20240111160242.149265-1-marpagan@redhat.com> (raw)

This RFC proposes a solution to keep protecting the fpga manager against
the unloading of the low-level control modules while addressing the
limitations of the current implementation. Currently, the code assumes
that the low-level module registers a driver for the parent device that
is later used to take the module's refcount. This proposal removes this
limitation by adding a module owner field to the fpga_manager struct
that can be set while registering the manager.

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

v5:
- Updated the documentation
- Removed kernel-doc comments for helper macros
v4:
- Use helper macros to set the owner module
v3:
- Improved locking
v2:
- Fixed protection against races during module removal

Marco Pagani (1):
  fpga: add an owner and use it to take the low-level module's refcount

 Documentation/driver-api/fpga/fpga-mgr.rst | 34 ++++----
 drivers/fpga/fpga-mgr.c                    | 93 ++++++++++++++--------
 include/linux/fpga/fpga-mgr.h              | 28 +++++--
 3 files changed, 102 insertions(+), 53 deletions(-)

base-commit: c849ecb2ae8413f86c84627cb0af06dffce4e215
-- 
2.43.0