Re: [PATCH] s390/pci: Stop usurping pdev->dev.groups

[Niklas Schnelle <schnelle@linux.ibm.com>]

On Mon, 2024-08-05 at 17:24 +0200, Lukas Wunner wrote:
> 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://msgid.link/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.
> 
> Signed-off-by: Lukas Wunner <lukas@wunner.de>
> ---
>  arch/s390/include/asm/pci.h |  9 ++++++++-
>  arch/s390/pci/Makefile      |  3 ++-
>  arch/s390/pci/pci.c         |  1 -
>  arch/s390/pci/pci_sysfs.c   | 14 ++++----------
>  drivers/pci/pci-sysfs.c     |  5 +++++
>  5 files changed, 19 insertions(+), 13 deletions(-)
> 
> diff --git a/arch/s390/include/asm/pci.h b/arch/s390/include/asm/pci.h
> index 30820a6..9d920ce 100644
> --- a/arch/s390/include/asm/pci.h
> +++ b/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;
>  
> diff --git a/arch/s390/pci/Makefile b/arch/s390/pci/Makefile
> index 0547a10..2c21f03 100644
> --- a/arch/s390/pci/Makefile
> +++ b/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
> diff --git a/arch/s390/pci/pci.c b/arch/s390/pci/pci.c
> index cff4838..bd9624c 100644
> --- a/arch/s390/pci/pci.c
> +++ b/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++) {
> diff --git a/arch/s390/pci/pci_sysfs.c b/arch/s390/pci/pci_sysfs.c
> index 0f4f1e8..1f81f6f 100644
> --- a/arch/s390/pci/pci_sysfs.c
> +++ b/arch/s390/pci/pci_sysfs.c
> @@ -197,7 +197,7 @@ static umode_t zpci_index_is_visible(struct kobject *kobj,
>  	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 umode_t zpci_index_is_visible(struct kobject *kobj,
>  	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 umode_t zpci_index_is_visible(struct kobject *kobj,
>  	&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,
> -};
> diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
> index 40cfa71..5d0f4db 100644
> --- a/drivers/pci/pci-sysfs.c
> +++ b/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 @@ static umode_t pcie_dev_attrs_are_visible(struct kobject *kobj,
>  	&pci_dev_acpi_attr_group,
>  #endif
>  	&pci_dev_resource_resize_group,
> +	ARCH_PCI_DEV_GROUPS
>  	NULL,
>  };
>  

Thanks for the patch and sorry for the delay I'll be on vacation
starting tomorrow and it's a bit busy. This makes sense to me and I
agree with Bjorn that this can go via the PCI tree, especially if it is
already useful there. I also gave this a compile and boot test on and
checked that the s390 specific PCI device attributes are still there.

Acked-by: Niklas Schnelle <schnelle@linux.ibm.com>