Re: [patch 32/39] PCI/MSI: Reorder functions in msi.c

[Bjorn Helgaas]

On Fri, Nov 11, 2022 at 02:55:06PM +0100, Thomas Gleixner wrote:
> From: Ahmed S. Darwish <darwi@xxxxxxxxxxxxx>
> 
> There is no way to navigate msi.c without banging the head against the wall
> every now and then because MSI and MSI-X specific functions are
> intermingled and the code flow is completely non-obvious.
> 
> Reorder everthing so common helpers, MSI and MSI-X specific functions are
> grouped together.

s/everthing/everything/

> Suggested-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Signed-off-by: Ahmed S. Darwish <darwi@xxxxxxxxxxxxx>
> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>

Acked-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>

I assume this is pure code movement, so I didn't even look at the
text below.

> ---
>  drivers/pci/msi/msi.c |  577 +++++++++++++++++++++++++-------------------------
>  1 file changed, 295 insertions(+), 282 deletions(-)
> 
> --- a/drivers/pci/msi/msi.c
> +++ b/drivers/pci/msi/msi.c
> @@ -16,6 +16,97 @@
>  int pci_msi_enable = 1;
>  int pci_msi_ignore_mask;
>  
> +/**
> + * pci_msi_supported - check whether MSI may be enabled on a device
> + * @dev: pointer to the pci_dev data structure of MSI device function
> + * @nvec: how many MSIs have been requested?
> + *
> + * Look at global flags, the device itself, and its parent buses
> + * to determine if MSI/-X are supported for the device. If MSI/-X is
> + * supported return 1, else return 0.
> + **/
> +static int pci_msi_supported(struct pci_dev *dev, int nvec)
> +{
> +	struct pci_bus *bus;
> +
> +	/* MSI must be globally enabled and supported by the device */
> +	if (!pci_msi_enable)
> +		return 0;
> +
> +	if (!dev || dev->no_msi)
> +		return 0;
> +
> +	/*
> +	 * You can't ask to have 0 or less MSIs configured.
> +	 *  a) it's stupid ..
> +	 *  b) the list manipulation code assumes nvec >= 1.
> +	 */
> +	if (nvec < 1)
> +		return 0;
> +
> +	/*
> +	 * Any bridge which does NOT route MSI transactions from its
> +	 * secondary bus to its primary bus must set NO_MSI flag on
> +	 * the secondary pci_bus.
> +	 *
> +	 * The NO_MSI flag can either be set directly by:
> +	 * - arch-specific PCI host bus controller drivers (deprecated)
> +	 * - quirks for specific PCI bridges
> +	 *
> +	 * or indirectly by platform-specific PCI host bridge drivers by
> +	 * advertising the 'msi_domain' property, which results in
> +	 * the NO_MSI flag when no MSI domain is found for this bridge
> +	 * at probe time.
> +	 */
> +	for (bus = dev->bus; bus; bus = bus->parent)
> +		if (bus->bus_flags & PCI_BUS_FLAGS_NO_MSI)
> +			return 0;
> +
> +	return 1;
> +}
> +
> +static void pcim_msi_release(void *pcidev)
> +{
> +	struct pci_dev *dev = pcidev;
> +
> +	dev->is_msi_managed = false;
> +	pci_free_irq_vectors(dev);
> +}
> +
> +/*
> + * Needs to be separate from pcim_release to prevent an ordering problem
> + * vs. msi_device_data_release() in the MSI core code.
> + */
> +static int pcim_setup_msi_release(struct pci_dev *dev)
> +{
> +	int ret;
> +
> +	if (!pci_is_managed(dev) || dev->is_msi_managed)
> +		return 0;
> +
> +	ret = devm_add_action(&dev->dev, pcim_msi_release, dev);
> +	if (!ret)
> +		dev->is_msi_managed = true;
> +	return ret;
> +}
> +
> +/*
> + * Ordering vs. devres: msi device data has to be installed first so that
> + * pcim_msi_release() is invoked before it on device release.
> + */
> +static int pci_setup_msi_context(struct pci_dev *dev)
> +{
> +	int ret = msi_setup_device_data(&dev->dev);
> +
> +	if (!ret)
> +		ret = pcim_setup_msi_release(dev);
> +	return ret;
> +}
> +
> +/*
> + * Helper functions for mask/unmask and MSI message handling
> + */
> +
>  void pci_msi_update_mask(struct msi_desc *desc, u32 clear, u32 set)
>  {
>  	raw_spinlock_t *lock = &to_pci_dev(desc->dev)->msi_lock;
> @@ -163,15 +254,8 @@ void pci_write_msi_msg(unsigned int irq,
>  }
>  EXPORT_SYMBOL_GPL(pci_write_msi_msg);
>  
> -void pci_free_msi_irqs(struct pci_dev *dev)
> -{
> -	pci_msi_teardown_msi_irqs(dev);
>  
> -	if (dev->msix_base) {
> -		iounmap(dev->msix_base);
> -		dev->msix_base = NULL;
> -	}
> -}
> +/* PCI/MSI specific functionality */
>  
>  static void pci_intx_for_msi(struct pci_dev *dev, int enable)
>  {
> @@ -190,111 +274,6 @@ static void pci_msi_set_enable(struct pc
>  	pci_write_config_word(dev, dev->msi_cap + PCI_MSI_FLAGS, control);
>  }
>  
> -/*
> - * Architecture override returns true when the PCI MSI message should be
> - * written by the generic restore function.
> - */
> -bool __weak arch_restore_msi_irqs(struct pci_dev *dev)
> -{
> -	return true;
> -}
> -
> -void __pci_restore_msi_state(struct pci_dev *dev)
> -{
> -	struct msi_desc *entry;
> -	u16 control;
> -
> -	if (!dev->msi_enabled)
> -		return;
> -
> -	entry = irq_get_msi_desc(dev->irq);
> -
> -	pci_intx_for_msi(dev, 0);
> -	pci_msi_set_enable(dev, 0);
> -	if (arch_restore_msi_irqs(dev))
> -		__pci_write_msi_msg(entry, &entry->msg);
> -
> -	pci_read_config_word(dev, dev->msi_cap + PCI_MSI_FLAGS, &control);
> -	pci_msi_update_mask(entry, 0, 0);
> -	control &= ~PCI_MSI_FLAGS_QSIZE;
> -	control |= (entry->pci.msi_attrib.multiple << 4) | PCI_MSI_FLAGS_ENABLE;
> -	pci_write_config_word(dev, dev->msi_cap + PCI_MSI_FLAGS, control);
> -}
> -
> -static void pci_msix_clear_and_set_ctrl(struct pci_dev *dev, u16 clear, u16 set)
> -{
> -	u16 ctrl;
> -
> -	pci_read_config_word(dev, dev->msix_cap + PCI_MSIX_FLAGS, &ctrl);
> -	ctrl &= ~clear;
> -	ctrl |= set;
> -	pci_write_config_word(dev, dev->msix_cap + PCI_MSIX_FLAGS, ctrl);
> -}
> -
> -void __pci_restore_msix_state(struct pci_dev *dev)
> -{
> -	struct msi_desc *entry;
> -	bool write_msg;
> -
> -	if (!dev->msix_enabled)
> -		return;
> -
> -	/* route the table */
> -	pci_intx_for_msi(dev, 0);
> -	pci_msix_clear_and_set_ctrl(dev, 0,
> -				PCI_MSIX_FLAGS_ENABLE | PCI_MSIX_FLAGS_MASKALL);
> -
> -	write_msg = arch_restore_msi_irqs(dev);
> -
> -	msi_lock_descs(&dev->dev);
> -	msi_for_each_desc(entry, &dev->dev, MSI_DESC_ALL) {
> -		if (write_msg)
> -			__pci_write_msi_msg(entry, &entry->msg);
> -		pci_msix_write_vector_ctrl(entry, entry->pci.msix_ctrl);
> -	}
> -	msi_unlock_descs(&dev->dev);
> -
> -	pci_msix_clear_and_set_ctrl(dev, PCI_MSIX_FLAGS_MASKALL, 0);
> -}
> -
> -static void pcim_msi_release(void *pcidev)
> -{
> -	struct pci_dev *dev = pcidev;
> -
> -	dev->is_msi_managed = false;
> -	pci_free_irq_vectors(dev);
> -}
> -
> -/*
> - * Needs to be separate from pcim_release to prevent an ordering problem
> - * vs. msi_device_data_release() in the MSI core code.
> - */
> -static int pcim_setup_msi_release(struct pci_dev *dev)
> -{
> -	int ret;
> -
> -	if (!pci_is_managed(dev) || dev->is_msi_managed)
> -		return 0;
> -
> -	ret = devm_add_action(&dev->dev, pcim_msi_release, dev);
> -	if (!ret)
> -		dev->is_msi_managed = true;
> -	return ret;
> -}
> -
> -/*
> - * Ordering vs. devres: msi device data has to be installed first so that
> - * pcim_msi_release() is invoked before it on device release.
> - */
> -static int pci_setup_msi_context(struct pci_dev *dev)
> -{
> -	int ret = msi_setup_device_data(&dev->dev);
> -
> -	if (!ret)
> -		ret = pcim_setup_msi_release(dev);
> -	return ret;
> -}
> -
>  static int msi_setup_msi_desc(struct pci_dev *dev, int nvec,
>  			      struct irq_affinity_desc *masks)
>  {
> @@ -415,6 +394,149 @@ static int msi_capability_init(struct pc
>  	return ret;
>  }
>  
> +int __pci_enable_msi_range(struct pci_dev *dev, int minvec, int maxvec,
> +			   struct irq_affinity *affd)
> +{
> +	int nvec;
> +	int rc;
> +
> +	if (!pci_msi_supported(dev, minvec) || dev->current_state != PCI_D0)
> +		return -EINVAL;
> +
> +	/* Check whether driver already requested MSI-X IRQs */
> +	if (dev->msix_enabled) {
> +		pci_info(dev, "can't enable MSI (MSI-X already enabled)\n");
> +		return -EINVAL;
> +	}
> +
> +	if (maxvec < minvec)
> +		return -ERANGE;
> +
> +	if (WARN_ON_ONCE(dev->msi_enabled))
> +		return -EINVAL;
> +
> +	nvec = pci_msi_vec_count(dev);
> +	if (nvec < 0)
> +		return nvec;
> +	if (nvec < minvec)
> +		return -ENOSPC;
> +
> +	if (nvec > maxvec)
> +		nvec = maxvec;
> +
> +	rc = pci_setup_msi_context(dev);
> +	if (rc)
> +		return rc;
> +
> +	for (;;) {
> +		if (affd) {
> +			nvec = irq_calc_affinity_vectors(minvec, nvec, affd);
> +			if (nvec < minvec)
> +				return -ENOSPC;
> +		}
> +
> +		rc = msi_capability_init(dev, nvec, affd);
> +		if (rc == 0)
> +			return nvec;
> +
> +		if (rc < 0)
> +			return rc;
> +		if (rc < minvec)
> +			return -ENOSPC;
> +
> +		nvec = rc;
> +	}
> +}
> +
> +/**
> + * pci_msi_vec_count - Return the number of MSI vectors a device can send
> + * @dev: device to report about
> + *
> + * This function returns the number of MSI vectors a device requested via
> + * Multiple Message Capable register. It returns a negative errno if the
> + * device is not capable sending MSI interrupts. Otherwise, the call succeeds
> + * and returns a power of two, up to a maximum of 2^5 (32), according to the
> + * MSI specification.
> + **/
> +int pci_msi_vec_count(struct pci_dev *dev)
> +{
> +	int ret;
> +	u16 msgctl;
> +
> +	if (!dev->msi_cap)
> +		return -EINVAL;
> +
> +	pci_read_config_word(dev, dev->msi_cap + PCI_MSI_FLAGS, &msgctl);
> +	ret = 1 << ((msgctl & PCI_MSI_FLAGS_QMASK) >> 1);
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL(pci_msi_vec_count);
> +
> +/*
> + * Architecture override returns true when the PCI MSI message should be
> + * written by the generic restore function.
> + */
> +bool __weak arch_restore_msi_irqs(struct pci_dev *dev)
> +{
> +	return true;
> +}
> +
> +void __pci_restore_msi_state(struct pci_dev *dev)
> +{
> +	struct msi_desc *entry;
> +	u16 control;
> +
> +	if (!dev->msi_enabled)
> +		return;
> +
> +	entry = irq_get_msi_desc(dev->irq);
> +
> +	pci_intx_for_msi(dev, 0);
> +	pci_msi_set_enable(dev, 0);
> +	if (arch_restore_msi_irqs(dev))
> +		__pci_write_msi_msg(entry, &entry->msg);
> +
> +	pci_read_config_word(dev, dev->msi_cap + PCI_MSI_FLAGS, &control);
> +	pci_msi_update_mask(entry, 0, 0);
> +	control &= ~PCI_MSI_FLAGS_QSIZE;
> +	control |= (entry->pci.msi_attrib.multiple << 4) | PCI_MSI_FLAGS_ENABLE;
> +	pci_write_config_word(dev, dev->msi_cap + PCI_MSI_FLAGS, control);
> +}
> +
> +void pci_msi_shutdown(struct pci_dev *dev)
> +{
> +	struct msi_desc *desc;
> +
> +	if (!pci_msi_enable || !dev || !dev->msi_enabled)
> +		return;
> +
> +	pci_msi_set_enable(dev, 0);
> +	pci_intx_for_msi(dev, 1);
> +	dev->msi_enabled = 0;
> +
> +	/* Return the device with MSI unmasked as initial states */
> +	desc = msi_first_desc(&dev->dev, MSI_DESC_ALL);
> +	if (!WARN_ON_ONCE(!desc))
> +		pci_msi_unmask(desc, msi_multi_mask(desc));
> +
> +	/* Restore dev->irq to its default pin-assertion IRQ */
> +	dev->irq = desc->pci.msi_attrib.default_irq;
> +	pcibios_alloc_irq(dev);
> +}
> +
> +/* PCI/MSI-X specific functionality */
> +
> +static void pci_msix_clear_and_set_ctrl(struct pci_dev *dev, u16 clear, u16 set)
> +{
> +	u16 ctrl;
> +
> +	pci_read_config_word(dev, dev->msix_cap + PCI_MSIX_FLAGS, &ctrl);
> +	ctrl &= ~clear;
> +	ctrl |= set;
> +	pci_write_config_word(dev, dev->msix_cap + PCI_MSIX_FLAGS, ctrl);
> +}
> +
>  static void __iomem *msix_map_region(struct pci_dev *dev,
>  				     unsigned int nr_entries)
>  {
> @@ -599,101 +721,6 @@ static int msix_capability_init(struct p
>  	return ret;
>  }
>  
> -/**
> - * pci_msi_supported - check whether MSI may be enabled on a device
> - * @dev: pointer to the pci_dev data structure of MSI device function
> - * @nvec: how many MSIs have been requested?
> - *
> - * Look at global flags, the device itself, and its parent buses
> - * to determine if MSI/-X are supported for the device. If MSI/-X is
> - * supported return 1, else return 0.
> - **/
> -static int pci_msi_supported(struct pci_dev *dev, int nvec)
> -{
> -	struct pci_bus *bus;
> -
> -	/* MSI must be globally enabled and supported by the device */
> -	if (!pci_msi_enable)
> -		return 0;
> -
> -	if (!dev || dev->no_msi)
> -		return 0;
> -
> -	/*
> -	 * You can't ask to have 0 or less MSIs configured.
> -	 *  a) it's stupid ..
> -	 *  b) the list manipulation code assumes nvec >= 1.
> -	 */
> -	if (nvec < 1)
> -		return 0;
> -
> -	/*
> -	 * Any bridge which does NOT route MSI transactions from its
> -	 * secondary bus to its primary bus must set NO_MSI flag on
> -	 * the secondary pci_bus.
> -	 *
> -	 * The NO_MSI flag can either be set directly by:
> -	 * - arch-specific PCI host bus controller drivers (deprecated)
> -	 * - quirks for specific PCI bridges
> -	 *
> -	 * or indirectly by platform-specific PCI host bridge drivers by
> -	 * advertising the 'msi_domain' property, which results in
> -	 * the NO_MSI flag when no MSI domain is found for this bridge
> -	 * at probe time.
> -	 */
> -	for (bus = dev->bus; bus; bus = bus->parent)
> -		if (bus->bus_flags & PCI_BUS_FLAGS_NO_MSI)
> -			return 0;
> -
> -	return 1;
> -}
> -
> -/**
> - * pci_msi_vec_count - Return the number of MSI vectors a device can send
> - * @dev: device to report about
> - *
> - * This function returns the number of MSI vectors a device requested via
> - * Multiple Message Capable register. It returns a negative errno if the
> - * device is not capable sending MSI interrupts. Otherwise, the call succeeds
> - * and returns a power of two, up to a maximum of 2^5 (32), according to the
> - * MSI specification.
> - **/
> -int pci_msi_vec_count(struct pci_dev *dev)
> -{
> -	int ret;
> -	u16 msgctl;
> -
> -	if (!dev->msi_cap)
> -		return -EINVAL;
> -
> -	pci_read_config_word(dev, dev->msi_cap + PCI_MSI_FLAGS, &msgctl);
> -	ret = 1 << ((msgctl & PCI_MSI_FLAGS_QMASK) >> 1);
> -
> -	return ret;
> -}
> -EXPORT_SYMBOL(pci_msi_vec_count);
> -
> -void pci_msi_shutdown(struct pci_dev *dev)
> -{
> -	struct msi_desc *desc;
> -
> -	if (!pci_msi_enable || !dev || !dev->msi_enabled)
> -		return;
> -
> -	pci_msi_set_enable(dev, 0);
> -	pci_intx_for_msi(dev, 1);
> -	dev->msi_enabled = 0;
> -
> -	/* Return the device with MSI unmasked as initial states */
> -	desc = msi_first_desc(&dev->dev, MSI_DESC_ALL);
> -	if (!WARN_ON_ONCE(!desc))
> -		pci_msi_unmask(desc, msi_multi_mask(desc));
> -
> -	/* Restore dev->irq to its default pin-assertion IRQ */
> -	dev->irq = desc->pci.msi_attrib.default_irq;
> -	pcibios_alloc_irq(dev);
> -}
> -
>  static int __pci_enable_msix(struct pci_dev *dev, struct msix_entry *entries,
>  			     int nvec, struct irq_affinity *affd, int flags)
>  {
> @@ -729,57 +756,23 @@ static int __pci_enable_msix(struct pci_
>  	return msix_capability_init(dev, entries, nvec, affd);
>  }
>  
> -void pci_msix_shutdown(struct pci_dev *dev)
> -{
> -	struct msi_desc *desc;
> -
> -	if (!pci_msi_enable || !dev || !dev->msix_enabled)
> -		return;
> -
> -	if (pci_dev_is_disconnected(dev)) {
> -		dev->msix_enabled = 0;
> -		return;
> -	}
> -
> -	/* Return the device with MSI-X masked as initial states */
> -	msi_for_each_desc(desc, &dev->dev, MSI_DESC_ALL)
> -		pci_msix_mask(desc);
> -
> -	pci_msix_clear_and_set_ctrl(dev, PCI_MSIX_FLAGS_ENABLE, 0);
> -	pci_intx_for_msi(dev, 1);
> -	dev->msix_enabled = 0;
> -	pcibios_alloc_irq(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,
> +			    int maxvec, struct irq_affinity *affd,
> +			    int flags)
>  {
> -	int nvec;
> -	int rc;
> -
> -	if (!pci_msi_supported(dev, minvec) || dev->current_state != PCI_D0)
> -		return -EINVAL;
> -
> -	/* Check whether driver already requested MSI-X IRQs */
> -	if (dev->msix_enabled) {
> -		pci_info(dev, "can't enable MSI (MSI-X already enabled)\n");
> -		return -EINVAL;
> -	}
> +	int rc, nvec = maxvec;
>  
>  	if (maxvec < minvec)
>  		return -ERANGE;
>  
> -	if (WARN_ON_ONCE(dev->msi_enabled))
> +	if (dev->msi_enabled) {
> +		pci_info(dev, "can't enable MSI-X (MSI already enabled)\n");
>  		return -EINVAL;
> +	}
>  
> -	nvec = pci_msi_vec_count(dev);
> -	if (nvec < 0)
> -		return nvec;
> -	if (nvec < minvec)
> -		return -ENOSPC;
> -
> -	if (nvec > maxvec)
> -		nvec = maxvec;
> +	if (WARN_ON_ONCE(dev->msix_enabled))
> +		return -EINVAL;
>  
>  	rc = pci_setup_msi_context(dev);
>  	if (rc)
> @@ -792,7 +785,7 @@ int __pci_enable_msi_range(struct pci_de
>  				return -ENOSPC;
>  		}
>  
> -		rc = msi_capability_init(dev, nvec, affd);
> +		rc = __pci_enable_msix(dev, entries, nvec, affd, flags);
>  		if (rc == 0)
>  			return nvec;
>  
> @@ -805,48 +798,68 @@ int __pci_enable_msi_range(struct pci_de
>  	}
>  }
>  
> -int __pci_enable_msix_range(struct pci_dev *dev,
> -			    struct msix_entry *entries, int minvec,
> -			    int maxvec, struct irq_affinity *affd,
> -			    int flags)
> +void __pci_restore_msix_state(struct pci_dev *dev)
>  {
> -	int rc, nvec = maxvec;
> +	struct msi_desc *entry;
> +	bool write_msg;
>  
> -	if (maxvec < minvec)
> -		return -ERANGE;
> +	if (!dev->msix_enabled)
> +		return;
>  
> -	if (dev->msi_enabled) {
> -		pci_info(dev, "can't enable MSI-X (MSI already enabled)\n");
> -		return -EINVAL;
> +	/* route the table */
> +	pci_intx_for_msi(dev, 0);
> +	pci_msix_clear_and_set_ctrl(dev, 0,
> +				PCI_MSIX_FLAGS_ENABLE | PCI_MSIX_FLAGS_MASKALL);
> +
> +	write_msg = arch_restore_msi_irqs(dev);
> +
> +	msi_lock_descs(&dev->dev);
> +	msi_for_each_desc(entry, &dev->dev, MSI_DESC_ALL) {
> +		if (write_msg)
> +			__pci_write_msi_msg(entry, &entry->msg);
> +		pci_msix_write_vector_ctrl(entry, entry->pci.msix_ctrl);
>  	}
> +	msi_unlock_descs(&dev->dev);
>  
> -	if (WARN_ON_ONCE(dev->msix_enabled))
> -		return -EINVAL;
> +	pci_msix_clear_and_set_ctrl(dev, PCI_MSIX_FLAGS_MASKALL, 0);
> +}
>  
> -	rc = pci_setup_msi_context(dev);
> -	if (rc)
> -		return rc;
> +void pci_msix_shutdown(struct pci_dev *dev)
> +{
> +	struct msi_desc *desc;
>  
> -	for (;;) {
> -		if (affd) {
> -			nvec = irq_calc_affinity_vectors(minvec, nvec, affd);
> -			if (nvec < minvec)
> -				return -ENOSPC;
> -		}
> +	if (!pci_msi_enable || !dev || !dev->msix_enabled)
> +		return;
>  
> -		rc = __pci_enable_msix(dev, entries, nvec, affd, flags);
> -		if (rc == 0)
> -			return nvec;
> +	if (pci_dev_is_disconnected(dev)) {
> +		dev->msix_enabled = 0;
> +		return;
> +	}
>  
> -		if (rc < 0)
> -			return rc;
> -		if (rc < minvec)
> -			return -ENOSPC;
> +	/* Return the device with MSI-X masked as initial states */
> +	msi_for_each_desc(desc, &dev->dev, MSI_DESC_ALL)
> +		pci_msix_mask(desc);
>  
> -		nvec = rc;
> +	pci_msix_clear_and_set_ctrl(dev, PCI_MSIX_FLAGS_ENABLE, 0);
> +	pci_intx_for_msi(dev, 1);
> +	dev->msix_enabled = 0;
> +	pcibios_alloc_irq(dev);
> +}
> +
> +/* Common interfaces */
> +
> +void pci_free_msi_irqs(struct pci_dev *dev)
> +{
> +	pci_msi_teardown_msi_irqs(dev);
> +
> +	if (dev->msix_base) {
> +		iounmap(dev->msix_base);
> +		dev->msix_base = NULL;
>  	}
>  }
>  
> +/* Misc. infrastructure */
> +
>  struct pci_dev *msi_desc_to_pci_dev(struct msi_desc *desc)
>  {
>  	return to_pci_dev(desc->dev);
>