[PATCH 00/10] Make PCI's devres API more consistent

Philipp Stanner
2024-01-15T14:47:14Z

¡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(-)

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2.43.0