Re: [PATCH v3 3/4] i2c: designware: Use the correct name of device-managed function

Dejin Zheng
2021-02-17T11:43:52Z

On Tue, Feb 16, 2021 at 06:46:01PM +0100, Krzysztof Wilczyński wrote:
Hi Krzysztof,
> Hi Dejin,
>
> Thank you for all the changes, looks good!
>
> You could improve the subject line, as it is very vague - what is the
> new function name more correct? Was the other and/or the previous one
> not correct? Seems like you are correcting a typo of sorts, rather than
> introducing a new function in this file.
>
If you have read the following commit comments, As you know, the
pci_alloc_irq_vectors() is not a real device-managed function. But
in some specific cases, it will act as an device-managed function.
Such naming will cause controversy, So In the case of need device-managed,
should be used pcim_alloc_irq_vectors(), an explicit device-managed
function. So the subject name is "Use the correct name of device-managed function".

> > Use the new function pcim_alloc_irq_vectors() to allocate IRQ vectors,
> > the pcim_alloc_irq_vectors() function, an explicit device-managed
> > version of pci_alloc_irq_vectors(). If pcim_enable_device() has been
> > called before, then pci_alloc_irq_vectors() is actually
> > a device-managed function. It is used here as a device-managed
> > function, So replace it with pcim_alloc_irq_vectors().
>
> The commit is good, but it could use some polish, so to speak.
>
> A few suggestions to think about:
>
> - What are we adding and/or changing, and why
> - Why is using pcim_alloc_irq_vectors(), which is part
> of the managed devices framework, a better alternative
> to the pci_alloc_irq_vectors()
> - And finally why this change allowed us to remove the
> pci_free_irq_vectors()
>
These are all explained by the device-managed function mechanism.

> > At the same time, simplify the error handling path.
>
> The change simplifies the error handling path, how? A line of two which
> explains how it has been achieved might help should someone reads the
> commit message in the future.
>
To put it simply, if the driver probe fail, the device-managed function
mechanism will automatically call pcim_release(), then the pci_free_irq_vectors()
will be executed. For details, please see the relevant code.

> [...]
> > if (controller->setup) {
> > r = controller->setup(pdev, controller);
> > - if (r) {
> > - pci_free_irq_vectors(pdev);
> > + if (r)
> > return r;
> > - }
> > }
> >
> > i2c_dw_adjust_bus_speed(dev);
> > @@ -246,10 +244,8 @@ static int i2c_dw_pci_probe(struct pci_dev *pdev,
> > i2c_dw_acpi_configure(&pdev->dev);
> >
> > r = i2c_dw_validate_speed(dev);
> > - if (r) {
> > - pci_free_irq_vectors(pdev);
> > + if (r)
> > return r;
> > - }
> >
> > i2c_dw_configure(dev);
> >
> > @@ -269,10 +265,8 @@ static int i2c_dw_pci_probe(struct pci_dev *pdev,
> > adap->nr = controller->bus_num;
> >
> > r = i2c_dw_probe(dev);
> > - if (r) {
> > - pci_free_irq_vectors(pdev);
> > + if (r)
> > return r;
> > - }
> >
> > pm_runtime_set_autosuspend_delay(&pdev->dev, 1000);
> > pm_runtime_use_autosuspend(&pdev->dev);
> > @@ -292,7 +286,6 @@ static void i2c_dw_pci_remove(struct pci_dev *pdev)
> >
> > i2c_del_adapter(&dev->adapter);
> > devm_free_irq(&pdev->dev, dev->irq, dev);
> > - pci_free_irq_vectors(pdev);
>
> If pcim_release() is called should the pci_driver's probe callback fail,
Yes, you guessed right.

> and I assume that this is precisely the case, then all of the above make
> sense in the view of using pcim_alloc_irq_vectors().
>
> Reviewed-by: Krzysztof Wilczyński <kw@linux.com>
>
> Krzysztof

BR,
Dejin