PCI: Make specifying PCI devices in kernel parameters reusable

Separate out the code to match a PCI device with a string (typically
originating from a kernel parameter) from the
pci_specified_resource_alignment() function into its own helper function.

While we are at it, this change fixes the kernel style of the function
(fixing a number of long lines and extra parentheses).

Additionally, make the analogous change to the kernel parameter
documentation: Separate the description of how to specify a PCI device
into its own section at the head of the "pci=" parameter.

This patch should have no functional alterations.

Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
[bhelgaas: use "device" instead of "slot" in documentation since that's the
usual language in the PCI specs]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Stephen Bates <sbates@raithlin.com>
Reviewed-by: Alex Williamson <alex.williamson@redhat.com>
Acked-by: Christian König <christian.koenig@amd.com>

2 files changed, 126 insertions, 59 deletions

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index efc7aa7a0670..ab36fb34ed01 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -2994,7 +2994,26 @@
                         See header of drivers/block/paride/pcd.c.
                         See also Documentation/blockdev/paride.txt.
 
-        pci=option[,option...]  [PCI] various PCI subsystem options:
+        pci=option[,option...]  [PCI] various PCI subsystem options.
+
+                                Some options herein operate on a specific device
+                                or a set of devices (<pci_dev>). These are
+                                specified in one of the following formats:
+
+                                [<domain>:]<bus>:<device>.<func>
+                                pci:<vendor>:<device>[:<subvendor>:<subdevice>]
+
+                                Note: the first format specifies a PCI
+                                bus/device/function address which may change
+                                if new hardware is inserted, if motherboard
+                                firmware changes, or due to changes caused
+                                by other kernel parameters. If the
+                                domain is left unspecified, it is
+                                taken to be zero. The second format
+                                selects devices using IDs from the
+                                configuration space which may match multiple
+                                devices in the system.
+
                 earlydump       [X86] dump PCI config space before the kernel
                                 changes anything
                 off             [X86] don't probe for the PCI bus
@@ -3123,11 +3142,10 @@
                                 window. The default value is 64 megabytes.
                 resource_alignment=
                                 Format:
-                                [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
-                                [<order of align>@]pci:<vendor>:<device>\
-                                                [:<subvendor>:<subdevice>][; ...]
+                                [<order of align>@]<pci_dev>[; ...]
                                 Specifies alignment and device to reassign
-                                aligned memory resources.
+                                aligned memory resources. How to
+                                specify the device is described above.
                                 If <order of align> is not specified,
                                 PAGE_SIZE is used as alignment.
                                 PCI-PCI bridge can be specified, if resource
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 97acba712e4e..1574b2da25e7 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -191,6 +191,92 @@ void __iomem *pci_ioremap_wc_bar(struct pci_dev *pdev, int bar)
 EXPORT_SYMBOL_GPL(pci_ioremap_wc_bar);
 #endif
 
+/**
+ * pci_dev_str_match - test if a string matches a device
+ * @dev:    the PCI device to test
+ * @p:      string to match the device against
+ * @endptr: pointer to the string after the match
+ *
+ * Test if a string (typically from a kernel parameter) matches a specified
+ * PCI device. The string may be of one of the following formats:
+ *
+ *   [<domain>:]<bus>:<device>.<func>
+ *   pci:<vendor>:<device>[:<subvendor>:<subdevice>]
+ *
+ * The first format specifies a PCI bus/device/function address which
+ * may change if new hardware is inserted, if motherboard firmware changes,
+ * or due to changes caused in kernel parameters. If the domain is
+ * left unspecified, it is taken to be 0.
+ *
+ * The second format matches devices using IDs in the configuration
+ * space which may match multiple devices in the system. A value of 0
+ * for any field will match all devices. (Note: this differs from
+ * in-kernel code that uses PCI_ANY_ID which is ~0; this is for
+ * legacy reasons and convenience so users don't have to specify
+ * FFFFFFFFs on the command line.)
+ *
+ * Returns 1 if the string matches the device, 0 if it does not and
+ * a negative error code if the string cannot be parsed.
+ */
+static int pci_dev_str_match(struct pci_dev *dev, const char *p,
+                             const char **endptr)
+{
+        int ret;
+        int seg, bus, slot, func, count;
+        unsigned short vendor, device, subsystem_vendor, subsystem_device;
+
+        if (strncmp(p, "pci:", 4) == 0) {
+                /* PCI vendor/device (subvendor/subdevice) IDs are specified */
+                p += 4;
+                ret = sscanf(p, "%hx:%hx:%hx:%hx%n", &vendor, &device,
+                             &subsystem_vendor, &subsystem_device, &count);
+                if (ret != 4) {
+                        ret = sscanf(p, "%hx:%hx%n", &vendor, &device, &count);
+                        if (ret != 2)
+                                return -EINVAL;
+
+                        subsystem_vendor = 0;
+                        subsystem_device = 0;
+                }
+
+                p += count;
+
+                if ((!vendor || vendor == dev->vendor) &&
+                    (!device || device == dev->device) &&
+                    (!subsystem_vendor ||
+                            subsystem_vendor == dev->subsystem_vendor) &&
+                    (!subsystem_device ||
+                            subsystem_device == dev->subsystem_device))
+                        goto found;
+
+        } else {
+                /* PCI Bus, Device, Function IDs are specified */
+                ret = sscanf(p, "%x:%x:%x.%x%n", &seg, &bus, &slot,
+                             &func, &count);
+                if (ret != 4) {
+                        seg = 0;
+                        ret = sscanf(p, "%x:%x.%x%n", &bus, &slot,
+                                     &func, &count);
+                        if (ret != 3)
+                                return -EINVAL;
+                }
+
+                p += count;
+
+                if (seg == pci_domain_nr(dev->bus) &&
+                    bus == dev->bus->number &&
+                    slot == PCI_SLOT(dev->devfn) &&
+                    func == PCI_FUNC(dev->devfn))
+                        goto found;
+        }
+
+        *endptr = p;
+        return 0;
+
+found:
+        *endptr = p;
+        return 1;
+}
 
 static int __pci_find_next_cap_ttl(struct pci_bus *bus, unsigned int devfn,
                                    u8 pos, int cap, int *ttl)
@@ -5454,10 +5540,10 @@ static DEFINE_SPINLOCK(resource_alignment_lock);
 static resource_size_t pci_specified_resource_alignment(struct pci_dev *dev,
                                                         bool *resize)
 {
-        int seg, bus, slot, func, align_order, count;
-        unsigned short vendor, device, subsystem_vendor, subsystem_device;
+        int align_order, count;
         resource_size_t align = pcibios_default_alignment();
-        char *p;
+        const char *p;
+        int ret;
 
         spin_lock(&resource_alignment_lock);
         p = resource_alignment_param;
@@ -5477,58 +5563,21 @@ static resource_size_t pci_specified_resource_alignment(struct pci_dev *dev,
                 } else {
                         align_order = -1;
                 }
-                if (strncmp(p, "pci:", 4) == 0) {
-                        /* PCI vendor/device (subvendor/subdevice) ids are specified */
-                        p += 4;
-                        if (sscanf(p, "%hx:%hx:%hx:%hx%n",
-                                &vendor, &device, &subsystem_vendor, &subsystem_device, &count) != 4) {
-                                if (sscanf(p, "%hx:%hx%n", &vendor, &device, &count) != 2) {
-                                        printk(KERN_ERR "PCI: Can't parse resource_alignment parameter: pci:%s\n",
-                                                p);
-                                        break;
-                                }
-                                subsystem_vendor = subsystem_device = 0;
-                        }
-                        p += count;
-                        if ((!vendor || (vendor == dev->vendor)) &&
-                                (!device || (device == dev->device)) &&
-                                (!subsystem_vendor || (subsystem_vendor == dev->subsystem_vendor)) &&
-                                (!subsystem_device || (subsystem_device == dev->subsystem_device))) {
-                                *resize = true;
-                                if (align_order == -1)
-                                        align = PAGE_SIZE;
-                                else
-                                        align = 1 << align_order;
-                                /* Found */
-                                break;
-                        }
-                }
-                else {
-                        if (sscanf(p, "%x:%x:%x.%x%n",
-                                &seg, &bus, &slot, &func, &count) != 4) {
-                                seg = 0;
-                                if (sscanf(p, "%x:%x.%x%n",
-                                                &bus, &slot, &func, &count) != 3) {
-                                        /* Invalid format */
-                                        printk(KERN_ERR "PCI: Can't parse resource_alignment parameter: %s\n",
-                                                p);
-                                        break;
-                                }
-                        }
-                        p += count;
-                        if (seg == pci_domain_nr(dev->bus) &&
-                                bus == dev->bus->number &&
-                                slot == PCI_SLOT(dev->devfn) &&
-                                func == PCI_FUNC(dev->devfn)) {
-                                *resize = true;
-                                if (align_order == -1)
-                                        align = PAGE_SIZE;
-                                else
-                                        align = 1 << align_order;
-                                /* Found */
-                                break;
-                        }
+
+                ret = pci_dev_str_match(dev, p, &p);
+                if (ret == 1) {
+                        *resize = true;
+                        if (align_order == -1)
+                                align = PAGE_SIZE;
+                        else
+                                align = 1 << align_order;
+                        break;
+                } else if (ret < 0) {
+                        pr_err("PCI: Can't parse resource_alignment parameter: %s\n",
+                               p);
+                        break;
                 }
+
                 if (*p != ';' && *p != ',') {
                         /* End of param or invalid format */
                         break;