s390/pci: Stop usurping pdev->dev.groups

Bjorn suggests using pdev->dev.groups for attribute_groups constructed on
PCI device enumeration:

  "Is it feasible to build an attribute group in pci_doe_init() and
   add it to dev->groups so device_add() will automatically add them?"
   https://lore.kernel.org/r/20231019165829.GA1381099@bhelgaas

Unfortunately on s390, pcibios_device_add() usurps pdev->dev.groups for
arch-specific attribute_groups, preventing its use for anything else.

Introduce an ARCH_PCI_DEV_GROUPS macro which arches can define in
<asm/pci.h>.  The macro is visible in drivers/pci/pci-sysfs.c through the
inclusion of <linux/pci.h>, which in turn includes <asm/pci.h>.

On s390, define the macro to the three attribute_groups previously assigned
to pdev->dev.groups.  Thereby pdev->dev.groups is made available for use by
the PCI core.

As a side effect, arch/s390/pci/pci_sysfs.c no longer needs to be compiled
into the kernel if CONFIG_SYSFS=n.

Link: https://lore.kernel.org/r/7b970f7923e373d1b23784721208f93418720485.1722870934.git.lukas@wunner.de
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Niklas Schnelle <schnelle@linux.ibm.com>

Author: l1k

arch/s390/include/asm/pci.h

@@ -191,7 +191,14 @@ static inline bool zdev_enabled(struct zpci_dev *zdev)
 	return (zdev->fh & (1UL << 31)) ? true : false;
 }
 
-extern const struct attribute_group *zpci_attr_groups[];
+extern const struct attribute_group zpci_attr_group;
+extern const struct attribute_group pfip_attr_group;
+extern const struct attribute_group zpci_ident_attr_group;
+
+#define ARCH_PCI_DEV_GROUPS &zpci_attr_group,		 \
+			    &pfip_attr_group,		 \
+			    &zpci_ident_attr_group,
+
 extern unsigned int s390_pci_force_floating __initdata;
 extern unsigned int s390_pci_no_rid;
 

arch/s390/pci/Makefile

@@ -3,7 +3,8 @@
 # Makefile for the s390 PCI subsystem.
 #
 
-obj-$(CONFIG_PCI)	+= pci.o pci_irq.o pci_clp.o pci_sysfs.o \
+obj-$(CONFIG_PCI)	+= pci.o pci_irq.o pci_clp.o \
 			   pci_event.o pci_debug.o pci_insn.o pci_mmio.o \
 			   pci_bus.o pci_kvm_hook.o
 obj-$(CONFIG_PCI_IOV)	+= pci_iov.o
+obj-$(CONFIG_SYSFS)	+= pci_sysfs.o

arch/s390/pci/pci.c

@@ -587,7 +587,6 @@ int pcibios_device_add(struct pci_dev *pdev)
 	if (pdev->is_physfn)
 		pdev->no_vf_scan = 1;
 
-	pdev->dev.groups = zpci_attr_groups;
 	zpci_map_resources(pdev);
 
 	for (i = 0; i < PCI_STD_NUM_BARS; i++) {

arch/s390/pci/pci_sysfs.c

@@ -197,7 +197,7 @@ static struct attribute *zpci_ident_attrs[] = {
 	NULL,
 };
 
-static struct attribute_group zpci_ident_attr_group = {
+const struct attribute_group zpci_ident_attr_group = {
 	.attrs = zpci_ident_attrs,
 	.is_visible = zpci_index_is_visible,
 };
@@ -223,7 +223,7 @@ static struct attribute *zpci_dev_attrs[] = {
 	NULL,
 };
 
-static struct attribute_group zpci_attr_group = {
+const struct attribute_group zpci_attr_group = {
 	.attrs = zpci_dev_attrs,
 	.bin_attrs = zpci_bin_attrs,
 };
@@ -235,14 +235,8 @@ static struct attribute *pfip_attrs[] = {
 	&dev_attr_segment3.attr,
 	NULL,
 };
-static struct attribute_group pfip_attr_group = {
+
+const struct attribute_group pfip_attr_group = {
 	.name = "pfip",
 	.attrs = pfip_attrs,
 };
-
-const struct attribute_group *zpci_attr_groups[] = {
-	&zpci_attr_group,
-	&pfip_attr_group,
-	&zpci_ident_attr_group,
-	NULL,
-};

drivers/pci/pci-sysfs.c

@@ -31,6 +31,10 @@
 #include <linux/aperture.h>
 #include "pci.h"
 
+#ifndef ARCH_PCI_DEV_GROUPS
+#define ARCH_PCI_DEV_GROUPS
+#endif
+
 static int sysfs_initialized;	/* = 0 */
 
 /* show configuration fields */
@@ -1624,6 +1628,7 @@ const struct attribute_group *pci_dev_groups[] = {
 	&pci_dev_acpi_attr_group,
 #endif
 	&pci_dev_resource_resize_group,
+	ARCH_PCI_DEV_GROUPS
 	NULL,
 };