xiaomi-sm8450/android_kernel_xiaomi_sm8450
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

PCI: Allow specifying devices using a base bus and path of devfns

Browse Source 
When specifying PCI devices on the kernel command line using a
bus/device/function address, bus numbers can change when adding or
replacing a device, changing motherboard firmware, or applying kernel
parameters like "pci=assign-buses".  When bus numbers change, it's likely
the command line tweak will be applied to the wrong device.

Therefore, it is useful to be able to specify devices with a base bus
number and the path of devfns needed to get to it, similar to the "device
scope" structure in the Intel VT-d spec, Section 8.3.1.

Thus, we add an option to specify devices in the following format:

  [<domain>:]<bus>:<device>.<func>[/<device>.<func>]*

The path can be any segment within the PCI hierarchy of any length and
determined through the use of 'lspci -t'.  When specified this way, it is
less likely that a renumbered bus will result in a valid device
specification and the tweak won't be applied to the wrong device.

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>
This commit is contained in:
Logan Gunthorpe
2018-07-30 10:18:38 -06:00
committed by Bjorn Helgaas
parent 07d8d7e57c
commit 45db33709c
2 changed files with 103 additions and 23 deletions
Download Patch File Download Diff File Expand all files Collapse all files

118
drivers/pci/pci.c
View File

@@ -191,6 +191,89 @@ void __iomem *pci_ioremap_wc_bar(struct pci_dev *pdev, int bar)
EXPORT_SYMBOL_GPL(pci_ioremap_wc_bar);
#endif
/**
* pci_dev_str_match_path - test if a path 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) formatted as a
* path of device/function addresses matches a PCI device. The string must
* be of the form:
*
* [<domain>:]<bus>:<device>.<func>[/<device>.<func>]*
*
* A path for a device can be obtained using 'lspci -t'. Using a path
* is more robust against bus renumbering than using only a single bus,
* device and function address.
*
* Returns 1 if the string matches the device, 0 if it does not and
* a negative error code if it fails to parse the string.
*/
static int pci_dev_str_match_path(struct pci_dev *dev, const char *path,
const char **endptr)
{
int ret;
int seg, bus, slot, func;
char *wpath, *p;
char end;
*endptr = strchrnul(path, ';');
wpath = kmemdup_nul(path, *endptr - path, GFP_KERNEL);
if (!wpath)
return -ENOMEM;
while (1) {
p = strrchr(wpath, '/');
if (!p)
break;
ret = sscanf(p, "/%x.%x%c", &slot, &func, &end);
if (ret != 2) {
ret = -EINVAL;
goto free_and_exit;
}
if (dev->devfn != PCI_DEVFN(slot, func)) {
ret = 0;
goto free_and_exit;
}
/*
* Note: we don't need to get a reference to the upstream
* bridge because we hold a reference to the top level
* device which should hold a reference to the bridge,
* and so on.
*/
dev = pci_upstream_bridge(dev);
if (!dev) {
ret = 0;
goto free_and_exit;
}
*p = 0;
}
ret = sscanf(wpath, "%x:%x:%x.%x%c", &seg, &bus, &slot,
&func, &end);
if (ret != 4) {
seg = 0;
ret = sscanf(wpath, "%x:%x.%x%c", &bus, &slot, &func, &end);
if (ret != 3) {
ret = -EINVAL;
goto free_and_exit;
}
}
ret = (seg == pci_domain_nr(dev->bus) &&
bus == dev->bus->number &&
dev->devfn == PCI_DEVFN(slot, func));
free_and_exit:
kfree(wpath);
return ret;
}
/**
* pci_dev_str_match - test if a string matches a device
* @dev: the PCI device to test
@@ -200,13 +283,16 @@ EXPORT_SYMBOL_GPL(pci_ioremap_wc_bar);
* 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>
* [<domain>:]<bus>:<device>.<func>[/<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.
* left unspecified, it is taken to be 0. In order to be robust against
* bus renumbering issues, a path of PCI device/function numbers may be used
* to address the specific device. The path for a device can be determined
* through the use of 'lspci -t'.
*
* The second format matches devices using IDs in the configuration
* space which may match multiple devices in the system. A value of 0
@@ -222,7 +308,7 @@ static int pci_dev_str_match(struct pci_dev *dev, const char *p,
const char **endptr)
{
int ret;
int seg, bus, slot, func, count;
int count;
unsigned short vendor, device, subsystem_vendor, subsystem_device;
if (strncmp(p, "pci:", 4) == 0) {
@@ -248,25 +334,15 @@ static int pci_dev_str_match(struct pci_dev *dev, const char *p,
(!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))
/*
* PCI Bus, Device, Function IDs are specified
* (optionally, may include a path of devfns following it)
*/
ret = pci_dev_str_match_path(dev, p, &p);
if (ret < 0)
return ret;
else if (ret)
goto found;
}