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Message-Id: <1392301502-22949-1-git-send-email-agordeev@redhat.com>
Date: Thu, 13 Feb 2014 15:25:02 +0100
From: Alexander Gordeev <agordeev@...hat.com>
To: linux-kernel@...r.kernel.org
Cc: Alexander Gordeev <agordeev@...hat.com>, linux-pci@...r.kernel.org
Subject: [PATCH] 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.
Cc: linux-pci@...r.kernel.org
Signed-off-by: Alexander Gordeev <agordeev@...hat.com>
---
Documentation/PCI/MSI-HOWTO.txt | 86 ++++++++++++++++++++++++++++++++++++++-
include/linux/pci.h | 20 +++++++++
2 files changed, 104 insertions(+), 2 deletions(-)
diff --git a/Documentation/PCI/MSI-HOWTO.txt b/Documentation/PCI/MSI-HOWTO.txt
index 96ee5eb..ae7307c 100644
--- a/Documentation/PCI/MSI-HOWTO.txt
+++ b/Documentation/PCI/MSI-HOWTO.txt
@@ -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 analized
+ */
+ 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)
diff --git a/include/linux/pci.h b/include/linux/pci.h
index fb57c89..33aa2ca 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -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
--
1.7.7.6
--
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