linux-kernel - Re: [PATCH 1/2] PCI: Export pci_parent_bus

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Date:   Tue, 8 Aug 2023 19:47:08 +0300 (EEST)
From:   Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To:     "Maciej W. Rozycki" <macro@...am.me.uk>
cc:     Bjorn Helgaas <bhelgaas@...gle.com>,
        Dennis Dalessandro <dennis.dalessandro@...nelisnetworks.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Leon Romanovsky <leon@...nel.org>, linux-pci@...r.kernel.org,
        linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] PCI: Export pci_parent_bus_reset() for drivers to
 use

On Tue, 20 Jun 2023, Maciej W. Rozycki wrote:

> Export pci_parent_bus_reset() so that drivers do not duplicate it.  
> Document the interface.
> 
> Signed-off-by: Maciej W. Rozycki <macro@...am.me.uk>
> ---
>  drivers/pci/pci.c   |   15 ++++++++++++++-
>  include/linux/pci.h |    1 +
>  2 files changed, 15 insertions(+), 1 deletion(-)
> 
> linux-pci-parent-bus-reset-export.diff
> Index: linux-macro/drivers/pci/pci.c
> ===================================================================
> --- linux-macro.orig/drivers/pci/pci.c
> +++ linux-macro/drivers/pci/pci.c
> @@ -5149,7 +5149,19 @@ int pci_bridge_secondary_bus_reset(struc
>  }
>  EXPORT_SYMBOL_GPL(pci_bridge_secondary_bus_reset);
>  
> -static int pci_parent_bus_reset(struct pci_dev *dev, bool probe)
> +/**
> + * pci_parent_bus_reset - Reset a device via its upstream PCI bridge
> + * @dev: Device to reset.
> + * @probe: Only check if reset is possible if TRUE, actually reset if FALSE.
> + *
> + * Perform a device reset by requesting a secondary bus reset via the
> + * device's immediate upstream PCI bridge.

>  Return 0 if successful or

Kernel doc has Return: section for return values.

> + * -ENOTTY if the reset failed or it could not have been issued in the
> + * first place because the device is not on a secondary bus of any PCI
> + * bridge or it wouldn't be the only device reset.  If probing, then
> + * only verify whether it would be possible to issue a reset.

I guess most of the in-depth explanation about reasons why reset 
might not me issuable could go into the longer description block.

-- 
 i.

> + */
> +int pci_parent_bus_reset(struct pci_dev *dev, bool probe)
>  {
>  	struct pci_dev *pdev;
>  
> @@ -5166,6 +5178,7 @@ static int pci_parent_bus_reset(struct p
>  
>  	return pci_bridge_secondary_bus_reset(dev->bus->self);
>  }
> +EXPORT_SYMBOL_GPL(pci_parent_bus_reset);
>  
>  static int pci_reset_hotplug_slot(struct hotplug_slot *hotplug, bool probe)
>  {
> Index: linux-macro/include/linux/pci.h
> ===================================================================
> --- linux-macro.orig/include/linux/pci.h
> +++ linux-macro/include/linux/pci.h
> @@ -1447,6 +1447,7 @@ int devm_request_pci_bus_resources(struc
>  
>  /* Temporary until new and working PCI SBR API in place */
>  int pci_bridge_secondary_bus_reset(struct pci_dev *dev);
> +int pci_parent_bus_reset(struct pci_dev *dev, bool probe);
>  
>  #define __pci_bus_for_each_res0(bus, res, ...)				\
>  	for (unsigned int __b = 0;					\
>