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Date: Tue, 21 Jul 2015 13:56:23 -0500
From: Jordan Hargrave <jharg93@...il.com>
To: Bjorn Helgaas <bhelgaas@...gle.com>
Cc: Jean Delvare <jdelvare@...e.de>, linux-kernel@...r.kernel.org,
linux-pci@...r.kernel.org,
Jordan Hargrave <Jordan_Hargrave@...l.com>
Subject: Re: [PATCH] Add support for reading SMBIOS Slot number for PCI devices
On Tue, Jul 21, 2015 at 1:09 PM, Bjorn Helgaas <bhelgaas@...gle.com> wrote:
> On Fri, Jul 10, 2015 at 05:02:46PM -0500, Jordan Hargrave wrote:
>> From: Jordan Hargrave <Jordan_Hargrave@...l.com>
>>
>> There currently isn't an easy way to determine which PCI devices belong to
>> system slots. This patch adds support to read SMBIOS Type 9 (System Slots).
>>
>> Signed-off-by: Jordan Hargrave <Jordan_Hargrave@...l.com>
>> ---
>> drivers/firmware/dmi_scan.c | 39 ++++++++++++++++++++
>> drivers/pci/pci-label.c | 89 +++++++++++++++++++++++++++++++++++++++++++++
>> include/linux/dmi.h | 1 +
>> 3 files changed, 129 insertions(+)
>>
>> diff --git a/drivers/firmware/dmi_scan.c b/drivers/firmware/dmi_scan.c
>> index ac1ce4a..8f95897 100644
>> --- a/drivers/firmware/dmi_scan.c
>> +++ b/drivers/firmware/dmi_scan.c
>> @@ -356,6 +356,41 @@ static void __init dmi_save_extended_devices(const struct dmi_header *dm)
>> dmi_save_one_device(*d & 0x7f, dmi_string_nosave(dm, *(d - 1)));
>> }
>>
>> +static void __init dmi_save_dev_slot(int instance, int segment, int bus, int devfn, const char *name)
>> +{
>> + struct dmi_dev_onboard *slot;
>> +
>> + slot = dmi_alloc(sizeof(*slot) + strlen(name) + 1);
>> + if (!slot) {
>> + printk(KERN_ERR "dmi_save_system_slot: out of memory.\n");
>
> You've got lots of data that might be useful in the printk: segment, bus,
> devfn, name.
>
>> + return;
>> + }
>> + slot->instance = instance;
>> + slot->segment = segment;
>> + slot->bus = bus;
>> + slot->devfn = devfn;
>> +
>> + strcpy((char *)&slot[1], name);
>> + slot->dev.type = DMI_DEV_TYPE_SYSTEM_SLOT;
>> + slot->dev.name = (char *)&slot[1];
>> + slot->dev.device_data = slot;
>> +
>> + list_add(&slot->dev.list, &dmi_devices);
>> +}
>> +
>> +
>> +static void __init dmi_save_system_slot(const struct dmi_header *dm)
>> +{
>> + const char *name;
>> + const u8 *d = (u8*)dm;
>> +
>> + if (dm->type == DMI_ENTRY_SYSTEM_SLOT && dm->length >= 0x11) {
>> + name = dmi_string_nosave(dm, *(d + 0x04));
>> + dmi_save_dev_slot(*(u16 *)(d + 0x09), *(u16 *)(d + 0xD),
>> + *(d + 0xF), *(d + 0x10), name);
>> + }
>> +}
>> +
>> static void __init count_mem_devices(const struct dmi_header *dm, void *v)
>> {
>> if (dm->type != DMI_ENTRY_MEM_DEVICE)
>> @@ -437,6 +472,10 @@ static void __init dmi_decode(const struct dmi_header *dm, void *dummy)
>> break;
>> case 41: /* Onboard Devices Extended Information */
>> dmi_save_extended_devices(dm);
>> + break;
>> + case 9: /* System Slots */
>> + dmi_save_system_slot(dm);
>> + break;
>> }
>> }
>>
>> diff --git a/drivers/pci/pci-label.c b/drivers/pci/pci-label.c
>> index 024b5c1..38dfb45 100644
>> --- a/drivers/pci/pci-label.c
>> +++ b/drivers/pci/pci-label.c
>> @@ -125,14 +125,103 @@ static struct attribute_group smbios_attr_group = {
>> .is_visible = smbios_instance_string_exist,
>> };
>>
>> +static int smbios_getslot(struct pci_dev *pdev)
>> +{
>> + struct pci_dev *sdev;
>> + struct dmi_dev_onboard *dslot;
>> + const struct dmi_device *dmi;
>> + u8 sub, sec, bus;
>> +
>> + dmi = NULL;
>> + if (pdev->is_virtfn) {
>> + /* Get Physical device for SR-IOV */
>> + pdev = pdev->physfn;
>> + }
>
> Use pci_physfn().
>
>> + bus = pdev->bus->number;
>> + while ((dmi = dmi_find_device(DMI_DEV_TYPE_SYSTEM_SLOT, NULL, dmi)) != NULL) {
>
> This loop doesn't match my naive expectation of how we should find a slot.
> I expected something like:
>
> - Look for DMI info that's an exact match for my D:B:D.F
> - Walk bridges upstream towards the root, looking for a subtree that
> includes pdev
>
It's a top-down approach vs bottom up. This way we only need to
search a single pci device for the slot... saves having to search up
the tree for all pci devices that *aren't* on a slot (eg embedded
devices will always search up to root without finding a slot entry).
>> + sec = sub = -1;
>> +
>> + dslot = dmi->device_data;
>> + sdev = pci_get_domain_bus_and_slot(dslot->segment, dslot->bus, dslot->devfn);
>
> This acquires a reference on the dev returned, so you need to dispose of
> that somewhere.
Ok
>
>> + if (sdev == NULL)
>> + continue;
>> +
>> + if (sdev->hdr_type == PCI_HEADER_TYPE_BRIDGE) {
>> + pci_read_config_byte(sdev, PCI_SECONDARY_BUS, &sec);
>> + pci_read_config_byte(sdev, PCI_SUBORDINATE_BUS, &sub);
>
> We should not have to read this out of config space; busn_res in struct
> pci_bus has this information already.
>
Ok
>> + if (bus >= sec && bus <= sub) {
>> + /* device is child of bridge */
>> + return dslot->instance;
>
> If you have a slot name for 0000:00:00.0 and a device at 0001:00:00.0, this
> will erroneously associate the domain 0 name with the domain 1 device.
>
OK will put in domain check earlier.
>> + }
>> + }
>> + if (pci_domain_nr(sdev->bus) == pci_domain_nr(pdev->bus) &&
>> + sdev->bus->number == pdev->bus->number &&
>> + PCI_SLOT(sdev->devfn) == PCI_SLOT(pdev->devfn)) {
>> + /* Match domain:bus:dev. If PCIE root, only match function */
>
> The PCIe part of this comment doesn't seem to match the code.
>
There can be multifunction devices with pcie root ports
00:01.0 PCIE Root (SMBIOS Slot 2)
00:01.1 PCIE Root (SMBIOS Slot 3)
00:02.2 PCIE Root
etc
and multifunction devices on a single device
01:00.0 Ethernet (SMBIOS slot points to function 0 only)
01:00.1 Ethernet
If SMBIOS slot points to PCIE root port, only match exact function
number. Otherwise match any function number.
>> + if (PCI_FUNC(sdev->devfn) == PCI_FUNC(pdev->devfn) ||
>> + pci_pcie_type(sdev) != PCI_EXP_TYPE_ROOT_PORT) {
>> + return dslot->instance;
>> + }
>> + }
>> + }
>> + return -ENODEV;
>> +}
>> +
>> +static ssize_t smbiosslot_show(struct device *dev,
>> + struct device_attribute *attr, char *buf)
>> +{
>> + struct pci_dev *pdev;
>> + int slot;
>> +
>> + pdev = to_pci_dev(dev);
>> + slot = smbios_getslot(pdev);
>> + if (slot > 0) {
>> + return scnprintf(buf, PAGE_SIZE, "%d\n", slot);
>> + }
>> + return 0;
>> +}
>> +
>> +static umode_t smbios_slot_exist(struct kobject *kobj, struct attribute *attr,
>> + int n)
>> +{
>> + struct device *dev;
>> + struct pci_dev *pdev;
>> +
>> + dev = container_of(kobj, struct device, kobj);
>> + pdev = to_pci_dev(dev);
>> +
>> + return (smbios_getslot(pdev) > 0) ? S_IRUGO : 0;
>> +}
>> +
>> +static struct device_attribute smbios_attr_slot = {
>> + .attr = {.name = "slot", .mode = 0444},
>> + .show = smbiosslot_show,
>> +};
>> +
>> +static struct attribute *smbios_slot_attributes[] = {
>> + &smbios_attr_slot.attr,
>> + NULL,
>> +};
>> +
>> +static struct attribute_group smbios_slot_attr_group = {
>> + .attrs = smbios_slot_attributes,
>> + .is_visible = smbios_slot_exist,
>> +};
>> +
>> static int pci_create_smbiosname_file(struct pci_dev *pdev)
>> {
>> + int rc;
>> +
>> + rc = sysfs_create_group(&pdev->dev.kobj, &smbios_slot_attr_group);
>> + if (rc != 0)
>> + return rc;
>> return sysfs_create_group(&pdev->dev.kobj, &smbios_attr_group);
>> }
>>
>> static void pci_remove_smbiosname_file(struct pci_dev *pdev)
>> {
>> sysfs_remove_group(&pdev->dev.kobj, &smbios_attr_group);
>> + sysfs_remove_group(&pdev->dev.kobj, &smbios_slot_attr_group);
>> }
>> #else
>> static inline int pci_create_smbiosname_file(struct pci_dev *pdev)
>> diff --git a/include/linux/dmi.h b/include/linux/dmi.h
>> index 5055ac3..09f42e7 100644
>> --- a/include/linux/dmi.h
>> +++ b/include/linux/dmi.h
>> @@ -22,6 +22,7 @@ enum dmi_device_type {
>> DMI_DEV_TYPE_IPMI = -1,
>> DMI_DEV_TYPE_OEM_STRING = -2,
>> DMI_DEV_TYPE_DEV_ONBOARD = -3,
>> + DMI_DEV_TYPE_SYSTEM_SLOT = -4,
>> };
>>
>> enum dmi_entry_type {
>> --
>> 1.8.3.1
>>
--
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