Commit 3ce4e860 authored by Alexander Gordeev's avatar Alexander Gordeev Committed by Bjorn Helgaas
Browse files

PCI/MSI: Add pci_enable_msi_exact() and pci_enable_msix_exact() 



The new functions are special cases for pci_enable_msi_range() and
pci_enable_msix_range() when a particular number of MSI or MSI-X
is needed.

By contrast with pci_enable_msi_range() and pci_enable_msix_range()
functions, pci_enable_msi_exact() and pci_enable_msix_exact()
return zero in case of success, which indicates MSI or MSI-X
interrupts have been successfully allocated.

Signed-off-by: default avatarAlexander Gordeev <agordeev@redhat.com>
Signed-off-by: default avatarBjorn Helgaas <bhelgaas@google.com>
parent 13f9653d

Documentation/PCI/MSI-HOWTO.txt

+84 −2
Original line number Diff line number Diff line
@@ -159,6 +159,11 @@ static int foo_driver_enable_msi(struct pci_dev *pdev, int nvec) 
	return pci_enable_msi_range(pdev, nvec, nvec);

}



Note, unlike pci_enable_msi_exact() function, which could be also used to

enable a particular number of MSI-X interrupts, pci_enable_msi_range()

returns either a negative errno or 'nvec' (not negative errno or 0 - as

pci_enable_msi_exact() does).



4.2.1.3 Single MSI mode



The most notorious example of the request type described above is
@@ -175,7 +180,22 @@ enable the single MSI mode, pci_enable_msi_range() returns either a 
negative errno or 1 (not negative errno or 0 - as pci_enable_msi()

does).



4.2.3 pci_disable_msi

4.2.3 pci_enable_msi_exact



int pci_enable_msi_exact(struct pci_dev *dev, int nvec)



This variation on pci_enable_msi_range() call allows a device driver to

request exactly 'nvec' MSIs.



If this function returns a negative number, it indicates an error and

the driver should not attempt to request any more MSI interrupts for

this device.



By contrast with pci_enable_msi_range() function, pci_enable_msi_exact()

returns zero in case of success, which indicates MSI interrupts have been

successfully allocated.



4.2.4 pci_disable_msi



void pci_disable_msi(struct pci_dev *dev)
@@ -303,6 +323,11 @@ static int foo_driver_enable_msix(struct foo_adapter *adapter, int nvec) 
				     nvec, nvec);

}



Note, unlike pci_enable_msix_exact() function, which could be also used to

enable a particular number of MSI-X interrupts, pci_enable_msix_range()

returns either a negative errno or 'nvec' (not negative errno or 0 - as

pci_enable_msix_exact() does).



4.3.1.3 Specific requirements to the number of MSI-X interrupts



As noted above, there could be devices that can not operate with just any
@@ -349,7 +374,64 @@ Note how pci_enable_msix_range() return value is analized for a fallback - 
any error code other than -ENOSPC indicates a fatal error and should not

be retried.



4.3.2 pci_disable_msix

4.3.2 pci_enable_msix_exact



int pci_enable_msix_exact(struct pci_dev *dev,

			  struct msix_entry *entries, int nvec)



This variation on pci_enable_msix_range() call allows a device driver to

request exactly 'nvec' MSI-Xs.



If this function returns a negative number, it indicates an error and

the driver should not attempt to allocate any more MSI-X interrupts for

this device.



By contrast with pci_enable_msix_range() function, pci_enable_msix_exact()

returns zero in case of success, which indicates MSI-X interrupts have been

successfully allocated.



Another version of a routine that enables MSI-X mode for a device with

specific requirements described in chapter 4.3.1.3 might look like this:



/*

 * Assume 'minvec' and 'maxvec' are non-zero

 */

static int foo_driver_enable_msix(struct foo_adapter *adapter,

				  int minvec, int maxvec)

{

	int rc;



	minvec = roundup_pow_of_two(minvec);

	maxvec = rounddown_pow_of_two(maxvec);



	if (minvec > maxvec)

		return -ERANGE;



retry:

	rc = pci_enable_msix_exact(adapter->pdev,

				   adapter->msix_entries, maxvec);



	/*

	 * -ENOSPC is the only error code allowed to be analyzed

	 */

	if (rc == -ENOSPC) {

		if (maxvec == 1)

			return -ENOSPC;



		maxvec /= 2;



		if (minvec > maxvec)

			return -ENOSPC;



		goto retry;

	} else if (rc < 0) {

		return rc;

	}



	return maxvec;

}



4.3.3 pci_disable_msix



void pci_disable_msix(struct pci_dev *dev)

include/linux/pci.h

+20 −0
Original line number Diff line number Diff line
@@ -1169,8 +1169,23 @@ void msi_remove_pci_irq_vectors(struct pci_dev *dev); 
void pci_restore_msi_state(struct pci_dev *dev);

int pci_msi_enabled(void);

int pci_enable_msi_range(struct pci_dev *dev, int minvec, int maxvec);

static inline int pci_enable_msi_exact(struct pci_dev *dev, int nvec)

{

	int rc = pci_enable_msi_range(dev, nvec, nvec);

	if (rc < 0)

		return rc;

	return 0;

}

int pci_enable_msix_range(struct pci_dev *dev, struct msix_entry *entries,

			  int minvec, int maxvec);

static inline int pci_enable_msix_exact(struct pci_dev *dev,

					struct msix_entry *entries, int nvec)

{

	int rc = pci_enable_msix_range(dev, entries, nvec, nvec);

	if (rc < 0)

		return rc;

	return 0;

}

#else

static inline int pci_msi_vec_count(struct pci_dev *dev) { return -ENOSYS; }

static inline int pci_enable_msi_block(struct pci_dev *dev, int nvec)
@@ -1189,9 +1204,14 @@ static inline int pci_msi_enabled(void) { return 0; } 
static inline int pci_enable_msi_range(struct pci_dev *dev, int minvec,

				       int maxvec)

{ return -ENOSYS; }

static inline int pci_enable_msi_exact(struct pci_dev *dev, int nvec)

{ return -ENOSYS; }

static inline int pci_enable_msix_range(struct pci_dev *dev,

		      struct msix_entry *entries, int minvec, int maxvec)

{ return -ENOSYS; }

static inline int pci_enable_msix_exact(struct pci_dev *dev,

		      struct msix_entry *entries, int nvec)

{ return -ENOSYS; }

#endif



#ifdef CONFIG_PCIEPORTBUS

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