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From: Philipp Stanner <pstanner@redhat.com>
To: Jonathan Corbet <corbet@lwn.net>,
	Hans de Goede <hdegoede@redhat.com>,
	Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
	Maxime Ripard <mripard@kernel.org>,
	Thomas Zimmermann <tzimmermann@suse.de>,
	David Airlie <airlied@gmail.com>,
	Daniel Vetter <daniel@ffwll.ch>,
	Bjorn Helgaas <bhelgaas@google.com>,
	Philipp Stanner <pstanner@redhat.com>,
	Sam Ravnborg <sam@ravnborg.org>,
	dakr@redhat.com
Cc: linux-doc@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	dri-devel@lists.freedesktop.org,
	linux-pci@vger.kernel.org
Subject: [PATCH 00/10] Make PCI's devres API more consistent
Date: Mon, 15 Jan 2024 15:46:11 +0100
Message-ID: <20240115144655.32046-2-pstanner@redhat.com>
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¡Hola!

PCI's devres API suffers several weaknesses:

1. There are functions prefixed with pcim_. Those are always managed
   counterparts to never-managed functions prefixed with pci_ – or so one
   would like to think. There are some apparently unmanaged functions
   (all region-request / release functions, and pci_intx()) which
   suddenly become managed once the user has initialized the device with
   pcim_enable_device() instead of pci_enable_device(). This "sometimes
   yes, sometimes no" nature of those functions is confusing and
   therefore bug-provoking. In fact, it has already caused a bug in DRM.
   The last patch in this series fixes that bug.
2. iomappings: Instead of giving each mapping its own callback, the
   existing API uses a statically allocated struct tracking one mapping
   per bar. This is not extensible. Especially, you can't create
   _ranged_ managed mappings that way, which many drivers want.
3. Managed request functions only exist as "plural versions" with a
   bit-mask as a parameter. That's quite over-engineered considering
   that each user only ever mapps one, maybe two bars.

This series:
- add a set of new "singular" devres functions that use devres the way
  its intended, with one callback per resource.
- deprecates the existing iomap-table mechanism.
- deprecates the hybrid nature of pci_ functions.
- preserves backwards compatibility so that drivers using the existing
  API won't notice any changes.
- adds documentation, especially some warning users about the
  complicated nature of PCI's devres.


Note that this series is based on my "unify pci_iounmap"-series from a
few weeks ago. [1]

I tested this on a x86 VM with a simple pci test-device with two
regions. Operates and reserves resources as intended on my system.
Kasan and kmemleak didn't find any problems.

I believe this series cleans the API up as much as possible without
having to port all existing drivers to the new API. Especially, I think
that this implementation is easy to extend if the need for new managed
functions arises :)

Greetings,
P.

[1] https://lore.kernel.org/lkml/20240111085540.7740-1-pstanner@redhat.com/


Philipp Stanner (10):
  pci: add new set of devres functions
  pci: deprecate iomap-table functions
  pci: warn users about complicated devres nature
  pci: devres: make devres region requests consistent
  pci: move enabled status bit to pci_dev struct
  pci: move pinned status bit to pci_dev struct
  pci: devres: give mwi its own callback
  pci: devres: give pci(m)_intx its own callback
  pci: devres: remove legacy pcim_release()
  drm/vboxvideo: fix mapping leaks

 Documentation/driver-api/pci/pci.rst  |   3 +
 drivers/gpu/drm/vboxvideo/vbox_main.c |  24 +-
 drivers/pci/devres.c                  | 996 ++++++++++++++++++++++----
 drivers/pci/iomap.c                   |  18 +
 drivers/pci/pci.c                     | 124 +++-
 drivers/pci/pci.h                     |  24 -
 include/linux/pci.h                   |  17 +
 7 files changed, 989 insertions(+), 217 deletions(-)

-- 
2.43.0