From: Bjorn Helgaas <helgaas@kernel.org>
To: Greg KH <gregkh@linuxfoundation.org>
Cc: Lee Jones <lee.jones@linaro.org>,
Leon Romanovsky <leon@kernel.org>,
"David E. Box" <david.e.box@linux.intel.com>,
hdegoede@redhat.com, bhelgaas@google.com,
andriy.shevchenko@linux.intel.com, srinivas.pandruvada@intel.com,
shuah@kernel.org, mgross@linux.intel.com,
linux-kernel@vger.kernel.org,
platform-driver-x86@vger.kernel.org,
linux-kselftest@vger.kernel.org, linux-pci@vger.kernel.org,
"Rafael J. Wysocki" <rjw@rjwysocki.net>
Subject: Re: [V2 2/6] driver core: auxiliary bus: Add driver data helpers
Date: Thu, 9 Dec 2021 10:32:45 -0600 [thread overview]
Message-ID: <20211209163245.GA245119@bhelgaas> (raw)
In-Reply-To: <YbBxPPPaQwlcgz/c@kroah.com>
[+cc Rafael, since I used generic PM as an example]
On Wed, Dec 08, 2021 at 09:47:56AM +0100, Greg KH wrote:
> On Wed, Dec 08, 2021 at 08:43:53AM +0000, Lee Jones wrote:
> > On Wed, 08 Dec 2021, Greg KH wrote:
> > > On Wed, Dec 08, 2021 at 09:03:16AM +0200, Leon Romanovsky wrote:
> > > > On Tue, Dec 07, 2021 at 09:14:44AM -0800, David E. Box wrote:
> > > > > Adds get/set driver data helpers for auxiliary devices.
> > > > >
> > > > > Signed-off-by: David E. Box <david.e.box@linux.intel.com>
> > > > > Reviewed-by: Mark Gross <markgross@kernel.org>
> > > > > ---
> > > > > V2
> > > > > - No changes
> > > > >
> > > > > include/linux/auxiliary_bus.h | 10 ++++++++++
> > > > > 1 file changed, 10 insertions(+)
> > > >
> > > > I would really like to see an explanation why such obfuscation is really
> > > > needed. dev_*_drvdata() is a standard way to access driver data.
> >
> > I wouldn't call it obfuscation, but it does looks like abstraction for
> > the sake of abstraction, which I usually push back on. What are the
> > technical benefits over using the dev_*() variant?
>
> See my response at:
> https://lore.kernel.org/r/YbBwOb6JvWkT3JWI@kroah.com
> for why it is a good thing to do.
>
> In short, driver authors should not have to worry about mixing
> bus-specific and low-level driver core functions.
In the very common situation of PCI drivers that use generic power
management, authors *do* have to use both (example from [1]):
ioh_gpio_probe(struct pci_dev *pdev) # pci_driver.probe()
pci_set_drvdata(pdev, chip);
ioh_gpio_remove(struct pci_dev *pdev) # pci_driver.remove()
struct ioh_gpio *chip = pci_get_drvdata(pdev);
ioh_gpio_suspend(struct device *dev) # pci_driver.driver.pm.suspend()
struct ioh_gpio *chip = dev_get_drvdata(dev); <--
The pci_driver methods receive a struct pci_dev and use the
pci_get_drvdata() wrapper.
The generic power management methods receive a struct device and use
the underlying dev_get_drvdata().
It's kind of ugly that readers have to know that pci_get_drvdata()
gives you the same thing as dev_get_drvdata().
I guess the generic PM methods could do something like:
pci_get_drvdata(to_pci_dev(dev));
but that seems a little bit circuitous. It's slightly wordier, but I
might prefer to just use this everywhere and skip the pci_* wrappers:
dev_get_drvdata(&pdev->dev);
Bjorn
[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/gpio/gpio-ml-ioh.c?id=v5.15#n505
next prev parent reply other threads:[~2021-12-09 16:32 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-07 17:14 [V2 0/6] Auxiliary bus driver support for Intel PCIe VSEC/DVSEC David E. Box
2021-12-07 17:14 ` [V2 1/6] PCI: Add #defines for accessing PCIe DVSEC fields David E. Box
2021-12-07 17:14 ` [V2 2/6] driver core: auxiliary bus: Add driver data helpers David E. Box
2021-12-07 17:35 ` Andy Shevchenko
2021-12-08 7:03 ` Leon Romanovsky
2021-12-08 7:07 ` Greg KH
2021-12-08 8:32 ` Leon Romanovsky
2021-12-08 8:43 ` Greg KH
2021-12-08 9:12 ` Leon Romanovsky
2021-12-08 10:14 ` Andy Shevchenko
2021-12-08 10:48 ` Leon Romanovsky
2021-12-08 8:43 ` Lee Jones
2021-12-08 8:47 ` Greg KH
2021-12-08 9:13 ` Lee Jones
2021-12-08 10:15 ` Andy Shevchenko
2021-12-09 16:32 ` Bjorn Helgaas [this message]
2021-12-09 16:54 ` Andy Shevchenko
2021-12-08 9:18 ` Leon Romanovsky
2021-12-07 17:14 ` [V2 3/6] platform/x86/intel: Move intel_pmt from MFD to Auxiliary Bus David E. Box
2021-12-07 17:14 ` [V2 4/6] platform/x86: Add Intel Software Defined Silicon driver David E. Box
2021-12-08 7:14 ` Leon Romanovsky
2021-12-08 10:42 ` David E. Box
2021-12-08 10:56 ` Leon Romanovsky
2021-12-07 17:14 ` [V2 5/6] sample/sdsi: Sample of SDSi provisiong using sysfs David E. Box
2021-12-07 17:14 ` [V2 6/6] selftests: sdsi: test sysfs setup David E. Box
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