linux-kernel - Re: [patch 27/39] PCI/MSI: Move pci_disable

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Date:   Wed, 16 Nov 2022 10:26:17 -0600
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
        Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
        linux-pci@...r.kernel.org, Bjorn Helgaas <bhelgaas@...gle.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Marc Zyngier <maz@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jason Gunthorpe <jgg@...lanox.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Alex Williamson <alex.williamson@...hat.com>,
        Kevin Tian <kevin.tian@...el.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Logan Gunthorpe <logang@...tatee.com>,
        Ashok Raj <ashok.raj@...el.com>, Jon Mason <jdmason@...zu.us>,
        Allen Hubbe <allenbh@...il.com>,
        "Ahmed S. Darwish" <darwi@...utronix.de>,
        Reinette Chatre <reinette.chatre@...el.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        linuxppc-dev@...ts.ozlabs.org
Subject: Re: [patch 27/39] PCI/MSI: Move pci_disable_msix() to api.c

On Fri, Nov 11, 2022 at 02:54:58PM +0100, Thomas Gleixner wrote:
> From: Ahmed S. Darwish <darwi@...utronix.de>
> 
> To distangle the maze in msi.c, all exported device-driver MSI APIs are
> now to be grouped in one file, api.c.
> 
> Move pci_disable_msix() and make its kernel-doc comprehensive.
> 
> Signed-off-by: Ahmed S. Darwish <darwi@...utronix.de>
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>

Acked-by: Bjorn Helgaas <bhelgaas@...gle.com>

Trivial question below.

> ---
>  drivers/pci/msi/api.c | 24 ++++++++++++++++++++++++
>  drivers/pci/msi/msi.c | 14 +-------------
>  drivers/pci/msi/msi.h |  1 +
>  3 files changed, 26 insertions(+), 13 deletions(-)
> ---
> diff --git a/drivers/pci/msi/api.c b/drivers/pci/msi/api.c
> index 83ea38ffa116..653a61868ae6 100644
> --- a/drivers/pci/msi/api.c
> +++ b/drivers/pci/msi/api.c
> @@ -112,6 +112,30 @@ int pci_enable_msix_range(struct pci_dev *dev, struct msix_entry *entries,
>  EXPORT_SYMBOL(pci_enable_msix_range);
>  
>  /**
> + * pci_disable_msix() - Disable MSI-X interrupt mode on device
> + * @dev: the PCI device to operate on
> + *
> + * Legacy device driver API to disable MSI-X interrupt mode on device,
> + * free earlier-allocated interrupt vectors, and restore INTx emulation.

Isn't INTx *emulation* a PCIe implementation detail?  Doesn't seem
relevant to callers that it's emulated.

> + * The PCI device Linux IRQ (@dev->irq) is restored to its default pin
> + * assertion IRQ. This is the cleanup pair of pci_enable_msix_range().
> + *
> + * NOTE: The newer pci_alloc_irq_vectors() / pci_free_irq_vectors() API
> + * pair should, in general, be used instead.
> + */
> +void pci_disable_msix(struct pci_dev *dev)
> +{
> +	if (!pci_msi_enabled() || !dev || !dev->msix_enabled)
> +		return;
> +
> +	msi_lock_descs(&dev->dev);
> +	pci_msix_shutdown(dev);
> +	pci_free_msi_irqs(dev);
> +	msi_unlock_descs(&dev->dev);
> +}
> +EXPORT_SYMBOL(pci_disable_msix);
> +
> +/**
>   * pci_alloc_irq_vectors() - Allocate multiple device interrupt vectors
>   * @dev:      the PCI device to operate on
>   * @min_vecs: minimum required number of vectors (must be >= 1)
> diff --git a/drivers/pci/msi/msi.c b/drivers/pci/msi/msi.c
> index 1226d66da992..6fa90d07d2e4 100644
> --- a/drivers/pci/msi/msi.c
> +++ b/drivers/pci/msi/msi.c
> @@ -736,7 +736,7 @@ static int __pci_enable_msix(struct pci_dev *dev, struct msix_entry *entries,
>  	return msix_capability_init(dev, entries, nvec, affd);
>  }
>  
> -static void pci_msix_shutdown(struct pci_dev *dev)
> +void pci_msix_shutdown(struct pci_dev *dev)
>  {
>  	struct msi_desc *desc;
>  
> @@ -758,18 +758,6 @@ static void pci_msix_shutdown(struct pci_dev *dev)
>  	pcibios_alloc_irq(dev);
>  }
>  
> -void pci_disable_msix(struct pci_dev *dev)
> -{
> -	if (!pci_msi_enable || !dev || !dev->msix_enabled)
> -		return;
> -
> -	msi_lock_descs(&dev->dev);
> -	pci_msix_shutdown(dev);
> -	pci_free_msi_irqs(dev);
> -	msi_unlock_descs(&dev->dev);
> -}
> -EXPORT_SYMBOL(pci_disable_msix);
> -
>  int __pci_enable_msi_range(struct pci_dev *dev, int minvec, int maxvec,
>  			   struct irq_affinity *affd)
>  {
> diff --git a/drivers/pci/msi/msi.h b/drivers/pci/msi/msi.h
> index 8c4a5289432d..77e2587f7e4f 100644
> --- a/drivers/pci/msi/msi.h
> +++ b/drivers/pci/msi/msi.h
> @@ -86,6 +86,7 @@ static inline __attribute_const__ u32 msi_multi_mask(struct msi_desc *desc)
>  
>  /* MSI internal functions invoked from the public APIs */
>  void pci_msi_shutdown(struct pci_dev *dev);
> +void pci_msix_shutdown(struct pci_dev *dev);
>  void pci_free_msi_irqs(struct pci_dev *dev);
>  int __pci_enable_msi_range(struct pci_dev *dev, int minvec, int maxvec, struct irq_affinity *affd);
>  int __pci_enable_msix_range(struct pci_dev *dev, struct msix_entry *entries, int minvec,
>