On Mon, 20 Sep 2021 15:28:52 +0100,
Kishon Vijay Abraham I <kishon@xxxxxx> wrote:
>
> Hi Marc,
>
> On 20/09/21 2:26 pm, Marc Zyngier wrote:
> > On Mon, 20 Sep 2021 07:41:31 +0100,
> > Kishon Vijay Abraham I <kishon@xxxxxx> wrote:
> >>
> >> Add two arguments to pci_walk_bus() [requestorID and mask], and add
> >> support in pci_walk_bus() to invoke the *callback* only for devices
> >> whose RequestorID after applying *mask* matches with *requestorID*
> >> passed as argument.
> >>
> >> This is done in preparation for calculating the total number of
> >> interrupt vectors that has to be supported by a specific GIC ITS device ID,
> >> specifically when "msi-map-mask" is populated in device tree.
> >>
> >> Signed-off-by: Kishon Vijay Abraham I <kishon@xxxxxx>
> >> ---
> >> drivers/pci/bus.c | 13 +++++++++----
> >> include/linux/pci.h | 7 +++++--
> >> 2 files changed, 14 insertions(+), 6 deletions(-)
> >>
> >> diff --git a/drivers/pci/bus.c b/drivers/pci/bus.c
> >> index 3cef835b375f..e381e639ceaa 100644
> >> --- a/drivers/pci/bus.c
> >> +++ b/drivers/pci/bus.c
> >> @@ -358,10 +358,12 @@ void pci_bus_add_devices(const struct pci_bus *bus)
> >> }
> >> EXPORT_SYMBOL(pci_bus_add_devices);
> >>
> >> -/** pci_walk_bus - walk devices on/under bus, calling callback.
> >> +/** __pci_walk_bus - walk devices on/under bus matching requestor ID, calling callback.
> >> * @top bus whose devices should be walked
> >> * @cb callback to be called for each device found
> >> * @userdata arbitrary pointer to be passed to callback.
> >> + * @rid Requestor ID that has to be matched for the callback to be invoked
> >> + * @mask Mask that has to be applied to pci_dev_id(), before compating it with @rid
> >> *
> >> * Walk the given bus, including any bridged devices
> >> * on buses under this bus. Call the provided callback
> >> @@ -371,8 +373,8 @@ EXPORT_SYMBOL(pci_bus_add_devices);
> >> * other than 0, we break out.
> >> *
> >> */
> >> -void pci_walk_bus(struct pci_bus *top, int (*cb)(struct pci_dev *, void *),
> >> - void *userdata)
> >> +void __pci_walk_bus(struct pci_bus *top, int (*cb)(struct pci_dev *, void *),
> >> + void *userdata, u32 rid, u32 mask)
> >> {
> >> struct pci_dev *dev;
> >> struct pci_bus *bus;
> >> @@ -399,13 +401,16 @@ void pci_walk_bus(struct pci_bus *top, int (*cb)(struct pci_dev *, void *),
> >> } else
> >> next = dev->bus_list.next;
> >>
> >> + if (mask != 0xffff && ((pci_dev_id(dev) & mask) != rid))
> >
> > Why the check for the mask? I also wonder whether the mask should apply
> > to the rid as well:
>
> If the mask is set for all 16bits, then there is not going to be two PCIe
> devices which gets the same ITS device ID right? So no need for calculating
> total number of vectors?
Are we really arguing about the cost of a compare+branch vs some
readability? Or is there an actual correctness issue here?
> >
> > if ((pci_dev_id(dev) & mask) != (rid & mask))
Because I think the above expression is a lot more readable (and
likely more correct) than what you are suggesting.
> >
> >> + continue;
> >> +
> >> retval = cb(dev, userdata);
> >> if (retval)
> >> break;
> >> }
> >> up_read(&pci_bus_sem);
> >> }
> >> -EXPORT_SYMBOL_GPL(pci_walk_bus);
> >> +EXPORT_SYMBOL_GPL(__pci_walk_bus);
> >>
> >> struct pci_bus *pci_bus_get(struct pci_bus *bus)
> >> {
> >> diff --git a/include/linux/pci.h b/include/linux/pci.h
> >> index cd8aa6fce204..8500fec56e50 100644
> >> --- a/include/linux/pci.h
> >> +++ b/include/linux/pci.h
> >> @@ -1473,14 +1473,17 @@ const struct pci_device_id *pci_match_id(const struct pci_device_id *ids,
> >> int pci_scan_bridge(struct pci_bus *bus, struct pci_dev *dev, int max,
> >> int pass);
> >>
> >> -void pci_walk_bus(struct pci_bus *top, int (*cb)(struct pci_dev *, void *),
> >> - void *userdata);
> >> +void __pci_walk_bus(struct pci_bus *top, int (*cb)(struct pci_dev *, void *),
> >> + void *userdata, u32 rid, u32 mask);
> >> int pci_cfg_space_size(struct pci_dev *dev);
> >> unsigned char pci_bus_max_busnr(struct pci_bus *bus);
> >> void pci_setup_bridge(struct pci_bus *bus);
> >> resource_size_t pcibios_window_alignment(struct pci_bus *bus,
> >> unsigned long type);
> >>
> >> +#define pci_walk_bus(top, cb, userdata) \
> >> + __pci_walk_bus((top), (cb), (userdata), 0x0, 0xffff)
> >
> > Please keep this close to the helper it replaces. I also really
> > dislike the use of this raw 0xffff. Don't we already have a named
> > constant that represents the mask for a RID?
>
> I didn't find one on quick look but let me check.
Worse case, you could create your own.
Thanks,
M.
--
Without deviation from the norm, progress is not possible.
