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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: Alexander Gordeev <agordeev@redhat.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
This commit is contained in:
Alexander Gordeev 2014-02-13 10:48:02 -07:00 committed by Bjorn Helgaas
parent 13f9653dab
commit 3ce4e860e5
2 changed files with 104 additions and 2 deletions
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86
Documentation/PCI/MSI-HOWTO.txt
View File

@ -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)

20
include/linux/pci.h
View File

@ -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