[PATCH 01/20] PCI: Convert dynamic "config" sysfs object into static

["Krzysztof Wilczyński" <kw@linux.com>]

The "config" sysfs object, which is a binary read-and-write attribute,
resides at the "/sys/bus/pci/devices/.../config" path and allows for
accessing either the legacy (PCI and PCI-X Mode 1) or the extended
(PCI-X Mode 2 and PCIe) device PCI configuration space.

At the moment, the static "config" sysfs object is dynamically created
when the pci_create_sysfs_dev_files() function executes that is part of
the PCI sysfs objects initialisation and when a device is added:

  late_initcall()
    pci_sysfs_init()
      pci_create_sysfs_dev_files()
        sysfs_create_bin_file()

  pci_bus_add_devices()
    pci_bus_add_device()
      pci_create_sysfs_dev_files()
        ...

And dynamically removed when the pci_remove_sysfs_dev_files() function
executes when the PCI device is stopped and removed:

  pci_stop_bus_device()
    pci_stop_dev()
      pci_remove_sysfs_dev_files()
        sysfs_remove_bin_file()

This attribute does not need to be created dynamically and removed
dynamically, and thus there is no need to also manage its create and
remove life cycle manually as the PCI driver core can do it when the
device is either added or removed.

Convert the "config" sysfs object created dynamically to static and use
the .is_bin_visible callback to set the correct sysfs object size
(either 256 bytes of 4 KiB) at runtime.

Then, add a newly created attribute group to the existing group called
"pci_dev_groups" to ensure that the "config" sysfs object would be
automatically included when the PCI driver initializes.

Suggested-by: Oliver O'Halloran <oohall@gmail.com>
Suggested-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Krzysztof Wilczyński <kw@linux.com>
---
 drivers/pci/pci-sysfs.c | 64 ++++++++++++++++-------------------------
 1 file changed, 25 insertions(+), 39 deletions(-)

diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index f8afd54ca3e1..dc14daf404f5 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -808,6 +808,29 @@ static ssize_t pci_write_config(struct file *filp, struct kobject *kobj,
 
 	return count;
 }
+static BIN_ATTR(config, 0644, pci_read_config, pci_write_config, 0);
+
+static struct bin_attribute *pci_dev_config_attrs[] = {
+	&bin_attr_config,
+	NULL,
+};
+
+static umode_t pci_dev_config_attr_is_visible(struct kobject *kobj,
+					      struct bin_attribute *a, int n)
+{
+	struct pci_dev *pdev = to_pci_dev(kobj_to_dev(kobj));
+
+	a->size = PCI_CFG_SPACE_SIZE;
+	if (pdev->cfg_size > PCI_CFG_SPACE_SIZE)
+		a->size = PCI_CFG_SPACE_EXP_SIZE;
+
+	return a->attr.mode;
+}
+
+static const struct attribute_group pci_dev_config_attr_group = {
+	.bin_attrs = pci_dev_config_attrs,
+	.is_bin_visible = pci_dev_config_attr_is_visible,
+};
 
 #ifdef HAVE_PCI_LEGACY
 /**
@@ -1284,26 +1307,6 @@ static ssize_t pci_read_rom(struct file *filp, struct kobject *kobj,
 	return count;
 }
 
-static const struct bin_attribute pci_config_attr = {
-	.attr =	{
-		.name = "config",
-		.mode = 0644,
-	},
-	.size = PCI_CFG_SPACE_SIZE,
-	.read = pci_read_config,
-	.write = pci_write_config,
-};
-
-static const struct bin_attribute pcie_config_attr = {
-	.attr =	{
-		.name = "config",
-		.mode = 0644,
-	},
-	.size = PCI_CFG_SPACE_EXP_SIZE,
-	.read = pci_read_config,
-	.write = pci_write_config,
-};
-
 static ssize_t reset_store(struct device *dev, struct device_attribute *attr,
 			   const char *buf, size_t count)
 {
@@ -1355,16 +1358,9 @@ int __must_check pci_create_sysfs_dev_files(struct pci_dev *pdev)
 	if (!sysfs_initialized)
 		return -EACCES;
 
-	if (pdev->cfg_size > PCI_CFG_SPACE_SIZE)
-		retval = sysfs_create_bin_file(&pdev->dev.kobj, &pcie_config_attr);
-	else
-		retval = sysfs_create_bin_file(&pdev->dev.kobj, &pci_config_attr);
-	if (retval)
-		goto err;
-
 	retval = pci_create_resource_files(pdev);
 	if (retval)
-		goto err_config_file;
+		goto err;
 
 	/* If the device has a ROM, try to expose it in sysfs. */
 	rom_size = pci_resource_len(pdev, PCI_ROM_RESOURCE);
@@ -1405,11 +1401,6 @@ int __must_check pci_create_sysfs_dev_files(struct pci_dev *pdev)
 	}
 err_resource_files:
 	pci_remove_resource_files(pdev);
-err_config_file:
-	if (pdev->cfg_size > PCI_CFG_SPACE_SIZE)
-		sysfs_remove_bin_file(&pdev->dev.kobj, &pcie_config_attr);
-	else
-		sysfs_remove_bin_file(&pdev->dev.kobj, &pci_config_attr);
 err:
 	return retval;
 }
@@ -1435,12 +1426,6 @@ void pci_remove_sysfs_dev_files(struct pci_dev *pdev)
 		return;
 
 	pci_remove_capabilities_sysfs(pdev);
-
-	if (pdev->cfg_size > PCI_CFG_SPACE_SIZE)
-		sysfs_remove_bin_file(&pdev->dev.kobj, &pcie_config_attr);
-	else
-		sysfs_remove_bin_file(&pdev->dev.kobj, &pci_config_attr);
-
 	pci_remove_resource_files(pdev);
 
 	if (pdev->rom_attr) {
@@ -1540,6 +1525,7 @@ static const struct attribute_group pci_dev_group = {
 
 const struct attribute_group *pci_dev_groups[] = {
 	&pci_dev_group,
+	&pci_dev_config_attr_group,
 	NULL,
 };
 
-- 
2.31.0