| Message ID | 20211106112606.192563-2-puranjay12@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Delegated to: | Bjorn Helgaas |
| Headers | show |
| Series | PCI: Update BAR #/window messages | expand |
On Sat, Nov 06, 2021 at 04:56:05PM +0530, Puranjay Mohan wrote: > + switch (i) { > + case 0: return "BAR 0"; > + case 1: return "BAR 1"; > + case 2: return "BAR 2"; > + case 3: return "BAR 3"; > + case 4: return "BAR 4"; > + case 5: return "BAR 5"; > + case PCI_ROM_RESOURCE: return "ROM"; > + #ifdef CONFIG_PCI_IOV > + case PCI_IOV_RESOURCES + 0: return "VF BAR 0"; > + case PCI_IOV_RESOURCES + 1: return "VF BAR 1"; > + case PCI_IOV_RESOURCES + 2: return "VF BAR 2"; > + case PCI_IOV_RESOURCES + 3: return "VF BAR 3"; > + case PCI_IOV_RESOURCES + 4: return "VF BAR 4"; > + case PCI_IOV_RESOURCES + 5: return "VF BAR 5"; > + #endif > + } Use a static const array of char * instead of a switch/case ladder to reduce LoC count and improve performance. See pcie_to_hpx3_type[] or state_conv[] in drivers/pci/pci-acpi.c for an example. Thanks, Lukas
On Sat, Nov 06, 2021 at 12:58:31PM +0100, Lukas Wunner wrote: > On Sat, Nov 06, 2021 at 04:56:05PM +0530, Puranjay Mohan wrote: > > + switch (i) { > > + case 0: return "BAR 0"; > > + case 1: return "BAR 1"; > > + case 2: return "BAR 2"; > > + case 3: return "BAR 3"; > > + case 4: return "BAR 4"; > > + case 5: return "BAR 5"; > > + case PCI_ROM_RESOURCE: return "ROM"; > > + #ifdef CONFIG_PCI_IOV > > + case PCI_IOV_RESOURCES + 0: return "VF BAR 0"; > > + case PCI_IOV_RESOURCES + 1: return "VF BAR 1"; > > + case PCI_IOV_RESOURCES + 2: return "VF BAR 2"; > > + case PCI_IOV_RESOURCES + 3: return "VF BAR 3"; > > + case PCI_IOV_RESOURCES + 4: return "VF BAR 4"; > > + case PCI_IOV_RESOURCES + 5: return "VF BAR 5"; > > + #endif > > + } > > Use a static const array of char * instead of a switch/case ladder > to reduce LoC count and improve performance. > > See pcie_to_hpx3_type[] or state_conv[] in drivers/pci/pci-acpi.c > for an example. I tried converting this and came up with the below. Is that the sort of thing you're thinking? Gcc *does* generate slightly smaller code for it, but Puranjay's original source code is smaller and IMO a little easier to read. And I just noticed that Puranjay's code nicely returns "unknown" for BAR 2-5 of bridges, while my code below does not. Could be fixed, of course, but would take a little more code. const char *pci_resource_name(struct pci_dev *dev, int i) { static const char *bar_name[] = { "BAR 0", "BAR 1", "BAR 2", "BAR 3", "BAR 4", "BAR 5", "ROM", #ifdef CONFIG_PCI_IOV "VF BAR 0", "VF BAR 1", "VF BAR 2", "VF BAR 3", "VF BAR 4", "VF BAR 5", #endif "bridge I/O window", "bridge mem window", "bridge mem pref window", }; static const char *cardbus_name[] = { "BAR 0", "unknown", "unknown", "unknown", "unknown", "unknown", "unknown", #ifdef CONFIG_PCI_IOV "unknown", "unknown", "unknown", "unknown", "unknown", "unknown", #endif "CardBus bridge I/O 0 window", "CardBus bridge I/O 1 window", "CardBus bridge mem 0 window", "CardBus bridge mem 1 window", }; if (dev->hdr_type == PCI_HEADER_TYPE_CARDBUS && i < ARRAY_SIZE(cardbus_name)) return cardbus_name[i]; else if (i < ARRAY_SIZE(bar_name)) return bar_name[i]; return "unknown"; }
On Fri, Nov 19, 2021 at 03:43:04PM -0600, Bjorn Helgaas wrote: > On Sat, Nov 06, 2021 at 12:58:31PM +0100, Lukas Wunner wrote: > > Use a static const array of char * instead of a switch/case ladder > > to reduce LoC count and improve performance. > > I tried converting this and came up with the below. Is that the sort > of thing you're thinking? Gcc *does* generate slightly smaller code > for it, but Puranjay's original source code is smaller and IMO a > little easier to read. Yes, that's what I had in mind. Aside from binary or source code size, retrieving the name from an array is just a quick direct access, whereas a switch/case ladder becomes a lot of conditional branches in binary code, which is slower. Another option is to use case ranges. See max3191x_set_config() in drivers/gpio/gpio-max3191x.c for an example. gcc is smart enough to generate an optimized set of conditional greater-than / less-than branches. That could be used to shorten your cardbus_name[] array. Thanks, Lukas
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index ce2ab62b64cf..1c2dfb2b9754 100644 --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -800,6 +800,53 @@ struct resource *pci_find_resource(struct pci_dev *dev, struct resource *res) } EXPORT_SYMBOL(pci_find_resource); +/** + * pci_resource_name - Return the name of the PCI resource. + * @dev: PCI device to query + * @i: index of the resource + * + * Returns the standard PCI resource(BAR) names according to their index. + */ +const char *pci_resource_name(struct pci_dev *dev, int i) +{ + if (dev->hdr_type == PCI_HEADER_TYPE_NORMAL) { + switch (i) { + case 0: return "BAR 0"; + case 1: return "BAR 1"; + case 2: return "BAR 2"; + case 3: return "BAR 3"; + case 4: return "BAR 4"; + case 5: return "BAR 5"; + case PCI_ROM_RESOURCE: return "ROM"; + #ifdef CONFIG_PCI_IOV + case PCI_IOV_RESOURCES + 0: return "VF BAR 0"; + case PCI_IOV_RESOURCES + 1: return "VF BAR 1"; + case PCI_IOV_RESOURCES + 2: return "VF BAR 2"; + case PCI_IOV_RESOURCES + 3: return "VF BAR 3"; + case PCI_IOV_RESOURCES + 4: return "VF BAR 4"; + case PCI_IOV_RESOURCES + 5: return "VF BAR 5"; + #endif + } + } else if (dev->hdr_type == PCI_HEADER_TYPE_BRIDGE) { + switch (i) { + case 0: return "BAR 0"; + case 1: return "BAR 1"; + case PCI_BRIDGE_IO_WINDOW: return "bridge I/O window"; + case PCI_BRIDGE_MEM_WINDOW: return "bridge mem window"; + case PCI_BRIDGE_PREF_MEM_WINDOW: return "bridge mem pref window"; + } + } else if (dev->hdr_type == PCI_HEADER_TYPE_CARDBUS) { + switch (i) { + case 0: return "BAR 0"; + case PCI_CB_BRIDGE_IO_0_WINDOW: return "CardBus bridge I/O 0 window"; + case PCI_CB_BRIDGE_IO_1_WINDOW: return "CardBus bridge I/O 1 window"; + case PCI_CB_BRIDGE_MEM_0_WINDOW: return "CardBus bridge mem 0 window"; + case PCI_CB_BRIDGE_MEM_1_WINDOW: return "CardBus bridge mem 1 window"; + } + } + return "unknown"; +} + /** * pci_wait_for_pending - wait for @mask bit(s) to clear in status word @pos * @dev: the PCI device to operate on diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h index 1cce56c2aea0..ee0738c7731a 100644 --- a/drivers/pci/pci.h +++ b/drivers/pci/pci.h @@ -281,6 +281,8 @@ void __pci_bus_assign_resources(const struct pci_bus *bus, struct list_head *fail_head); bool pci_bus_clip_resource(struct pci_dev *dev, int idx); +const char *pci_resource_name(struct pci_dev *dev, int i); + void pci_reassigndev_resource_alignment(struct pci_dev *dev); void pci_disable_bridge_window(struct pci_dev *dev); struct pci_bus *pci_bus_get(struct pci_bus *bus);
The PCI logs messages print the register offsets at some places and BAR numbers at other places. There is no uniformity in this logging mechanism. It would be better to print names than register offsets. Add a helper function that aids in printing more meaningful information about the BAR numbers like "VF BAR", "ROM", "Bridge Window", etc. This function can be called while printing PCI log messages. Signed-off-by: Puranjay Mohan <puranjay12@gmail.com> --- drivers/pci/pci.c | 47 +++++++++++++++++++++++++++++++++++++++++++++++ drivers/pci/pci.h | 2 ++ 2 files changed, 49 insertions(+)