Re: [PATCH v9 4/8] vpci: Hide extended capability when it fails to initialize

[Nicola Vetrini <nicola.vetrini@xxxxxxxxxxx>]

On 2025-07-30 12:42, Nicola Vetrini wrote:
> On 2025-07-30 11:50, Jan Beulich wrote:
> > On 28.07.2025 07:03, Jiqian Chen wrote:
> > > +static int vpci_ext_capability_hide(
> > > +    const struct pci_dev *pdev, unsigned int cap)
> > > +{
> > > +    const unsigned int offset = pci_find_ext_capability(pdev->sbdf, 
> > > cap);
> > > +    struct vpci_register *r, *prev_r;
> > > +    struct vpci *vpci = pdev->vpci;
> > > +    uint32_t header, pre_header;
> > > +
> > > +    if ( offset < PCI_CFG_SPACE_SIZE )
> > > +    {
> > > +        ASSERT_UNREACHABLE();
> > > +        return 0;
> > > +    }
> > > +
> > > +    spin_lock(&vpci->lock);
> > > +    r = vpci_get_register(vpci, offset, 4);
> > > +    if ( !r )
> > > +    {
> > > +        spin_unlock(&vpci->lock);
> > > +        return -ENODEV;
> > > +    }
> > > +
> > > +    header = (uint32_t)(uintptr_t)r->private;
> > > +    if ( offset == PCI_CFG_SPACE_SIZE )
> > > +    {
> > > +        if ( PCI_EXT_CAP_NEXT(header) <= PCI_CFG_SPACE_SIZE )
> > > +            r->private = (void *)(uintptr_t)0;
> > Eclair regards this a Misra rule 11.9 violation. Elsewhere we use 
> > (void *)0,
> > which I then would conclude is "fine". But I can't say why that is. 
> > Cc-ing
> > Bugseng for a possible explanation.
> Hi Jan,
>
> I only see
>
> 0|$ git grep "(void\*)0"
> xen/include/xen/types.h:#define NULL ((void*)0)
>
> which is fine for R11.9 of course. As Andrew noted, I don't see the 
> need for the use of uintptr_t either.
Oh, I missed forms using a space before the pointer. In any case, from 
the rule's Amplification: "Note: a null pointer constant of the form 
(void *)0 is permitted, whether or not it was expanded from NULL."
--
Nicola Vetrini, B.Sc.
Software Engineer
BUGSENG (https://bugseng.com)
LinkedIn: https://www.linkedin.com/in/nicola-vetrini-a42471253