[+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@xxxxxxxxxxxxxxx> > > > > > Reviewed-by: Mark Gross <markgross@xxxxxxxxxx> > > > > > --- > > > > > 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@xxxxxxxxx > 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
