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Message-ID: <3b2746f7779aa5dc39a406593dae37c4a8da676d.camel@redhat.com>
Subject: Re: [PATCH v2 00/10] Make PCI's devres API more consistent
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>, 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
Date: Tue, 23 Jan 2024 11:23:20 +0100
In-Reply-To: <20240123094317.15958-1-pstanner@redhat.com>
References: <20240123094317.15958-1-pstanner@redhat.com>
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Forgot to add a few changes to the changelog:

On Tue, 2024-01-23 at 10:42 +0100, Philipp Stanner wrote:
> Changes in v2:
> =C2=A0 - Make commit head lines congruent with PCI's style (Bjorn)
> =C2=A0 - Add missing error checks for devm_add_action(). (Andy)
> =C2=A0 - Repair the "Returns: " marks for docu generation (Andy)
> =C2=A0 - Initialize the addr_devres struct with memset(). (Andy)
> =C2=A0 - Make pcim_intx() a PCI-internal function so that new drivers
> won't
> =C2=A0=C2=A0=C2=A0 be encouraged to use the outdated pci_intx() mechanism=
.
> =C2=A0=C2=A0=C2=A0 (Andy / Philipp)
> =C2=A0 - Fix grammar and spelling (Bjorn)
> =C2=A0 - Be more precise on why pcim_iomap_table() is problematic (Bjorn)
> =C2=A0 - Provide the actual structs' and functions' names in the commit
> =C2=A0=C2=A0=C2=A0 messages (Bjorn)
> =C2=A0 - Remove redundant variable initializers (Andy)
> =C2=A0 - Regroup PM bitfield members in struct pci_dev (Andy)
> =C2=A0 - Consistently use the term "PCI devres API"; also in Patch #10
> (Bjorn)

 * Make pcim_intx() visible only for the PCI subsystem so that new   =20
   drivers won't use this outdated API (Andy, Myself)
 * Add a NOTE to pcim_iomap() to warn about this function being the    onee
   xception that does just return NULL.

This v2 now contains most of the feedback, except the ones Andy and I
haven't agreed on yet.

Thx,
P.

>=20
>=20
> =C2=A1Hola!
>=20
> PCI's devres API suffers several weaknesses:
>=20
> 1. There are functions prefixed with pcim_. Those are always managed
> =C2=A0=C2=A0 counterparts to never-managed functions prefixed with pci_ =
=E2=80=93 or so
> one
> =C2=A0=C2=A0 would like to think. There are some apparently unmanaged fun=
ctions
> =C2=A0=C2=A0 (all region-request / release functions, and pci_intx()) whi=
ch
> =C2=A0=C2=A0 suddenly become managed once the user has initialized the de=
vice
> with
> =C2=A0=C2=A0 pcim_enable_device() instead of pci_enable_device(). This
> "sometimes
> =C2=A0=C2=A0 yes, sometimes no" nature of those functions is confusing an=
d
> =C2=A0=C2=A0 therefore bug-provoking. In fact, it has already caused a bu=
g in
> DRM.
> =C2=A0=C2=A0 The last patch in this series fixes that bug.
> 2. iomappings: Instead of giving each mapping its own callback, the
> =C2=A0=C2=A0 existing API uses a statically allocated struct tracking one
> mapping
> =C2=A0=C2=A0 per bar. This is not extensible. Especially, you can't creat=
e
> =C2=A0=C2=A0 _ranged_ managed mappings that way, which many drivers want.
> 3. Managed request functions only exist as "plural versions" with a
> =C2=A0=C2=A0 bit-mask as a parameter. That's quite over-engineered consid=
ering
> =C2=A0=C2=A0 that each user only ever mapps one, maybe two bars.
>=20
> This series:
> - add a set of new "singular" devres functions that use devres the
> way
> =C2=A0 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
> =C2=A0 API won't notice any changes.
> - adds documentation, especially some warning users about the
> =C2=A0 complicated nature of PCI's devres.
>=20
>=20
> Note that this series is based on my "unify pci_iounmap"-series from
> a
> few weeks ago. [1]
>=20
> 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.
>=20
> 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 :)
>=20
> Greetings,
> P.
>=20
> Philipp Stanner (10):
> =C2=A0 PCI: add new set of devres functions
> =C2=A0 PCI: deprecate iomap-table functions
> =C2=A0 PCI: warn users about complicated devres nature
> =C2=A0 PCI: make devres region requests consistent
> =C2=A0 PCI: move dev-enabled status bit to struct pci_dev
> =C2=A0 PCI: move pinned status bit to struct pci_dev
> =C2=A0 PCI: give pcim_set_mwi() its own devres callback
> =C2=A0 PCI: give pci(m)_intx its own devres callback
> =C2=A0 PCI: remove legacy pcim_release()
> =C2=A0 drm/vboxvideo: fix mapping leaks
>=20
> =C2=A0Documentation/driver-api/pci/pci.rst=C2=A0 |=C2=A0=C2=A0=C2=A0 3 +
> =C2=A0drivers/gpu/drm/vboxvideo/vbox_main.c |=C2=A0=C2=A0 24 +-
> =C2=A0drivers/pci/devres.c=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 | 1015 ++++++++++=
+++++++++++--
> --
> =C2=A0drivers/pci/iomap.c=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 |=C2=A0=C2=A0 =
18 +
> =C2=A0drivers/pci/pci.c=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 |=
=C2=A0 123 ++-
> =C2=A0drivers/pci/pci.h=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 |=
=C2=A0=C2=A0 25 +-
> =C2=A0include/linux/pci.h=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 |=C2=A0=C2=A0 =
18 +-
> =C2=A07 files changed, 1011 insertions(+), 215 deletions(-)
>=20