On 2025/4/11 16:00, Jan Beulich wrote: > On 11.04.2025 04:51, Chen, Jiqian wrote: >> On 2025/4/10 20:34, Jan Beulich wrote: >>> On 09.04.2025 08:45, Jiqian Chen wrote: >>>> --- a/xen/drivers/pci/pci.c >>>> +++ b/xen/drivers/pci/pci.c >>>> @@ -40,7 +40,7 @@ unsigned int pci_find_cap_offset(pci_sbdf_t sbdf, >>>> unsigned int cap) >>>> } >>>> >>>> unsigned int pci_find_next_cap_ttl(pci_sbdf_t sbdf, unsigned int pos, >>>> - const unsigned int caps[], unsigned >>>> int n, >>>> + const unsigned int *caps, unsigned int >>>> n, >>> >>> I don't follow the need for this change. >> This changed is for my next patch "vpci/header: Emulate legacy capability >> list for host". >> Currently, vpci only emulates capability list for domU, not for dom0. >> For domU, vpci exposes a fixed capability array which calls "supported_caps". >> My changes want to emulate capability list for dom0. >> I think vpci should expose all devices capabilities to dom0. >> When I emulate it, I need to iterate over all capabilities without another >> fixed array, >> so I need this function to return the position of next capability directly >> when passing a zero length array to this function. > > This doesn't answer my question. The change you need for the next patch is > the hunk below, not the one above. Aiui at least. Ah, yes. I will abandon changing this function definition in next version since it just needs to check "n == 0".
> >>>> @@ -55,6 +55,10 @@ unsigned int pci_find_next_cap_ttl(pci_sbdf_t sbdf, >>>> unsigned int pos, >>>> >>>> if ( id == 0xff ) >>>> break; >>>> + >>>> + if ( !caps || n == 0 ) >>>> + return pos; >>> >>> Checking n to be zero ought to suffice here? In that case it doesn't matter >>> what caps is. Plus if n is non-zero, it clearly is an error if caps was >>> NULL. >> Two checking is to prevent null pointer errors. >> But as you said, if checking n to be zero is enough, then I don't need to >> change the definition of this function. >> I will change in next version. > > If you really wanted to, you could add e.g. ASSERT(caps) after this if(). OK, will add in next version, too. > > Jan -- Best regards, Jiqian Chen.
