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author | Alexander Gordeev <agordeev@redhat.com> | 2013-12-30 08:28:13 +0100 |
---|---|---|
committer | Bjorn Helgaas <bhelgaas@google.com> | 2014-01-03 17:17:55 -0700 |
commit | d1ac1d2622e8f0fd2a25127a8649d135b54db8a9 (patch) | |
tree | 9b267fa3c5d97fc9c6c65877a9d493d407258abe | |
parent | 52179dc9edc3b7a2b3bb01cbb1b6c96f6d05fc73 (diff) | |
download | linux-stable-d1ac1d2622e8f0fd2a25127a8649d135b54db8a9.tar.gz linux-stable-d1ac1d2622e8f0fd2a25127a8649d135b54db8a9.tar.bz2 linux-stable-d1ac1d2622e8f0fd2a25127a8649d135b54db8a9.zip |
PCI/MSI: Add pci_msi_vec_count()
Device drivers can use this interface to obtain the maximum number of MSI
interrupts the device supports and use that number, e.g., in a subsequent
call to pci_enable_msi_block().
Signed-off-by: Alexander Gordeev <agordeev@redhat.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Tejun Heo <tj@kernel.org>
-rw-r--r-- | Documentation/PCI/MSI-HOWTO.txt | 15 | ||||
-rw-r--r-- | drivers/pci/msi.c | 41 | ||||
-rw-r--r-- | include/linux/pci.h | 6 |
3 files changed, 54 insertions, 8 deletions
diff --git a/Documentation/PCI/MSI-HOWTO.txt b/Documentation/PCI/MSI-HOWTO.txt index a4d174e95413..a8b41788dfde 100644 --- a/Documentation/PCI/MSI-HOWTO.txt +++ b/Documentation/PCI/MSI-HOWTO.txt @@ -169,6 +169,21 @@ on any interrupt for which it previously called request_irq(). Failure to do so results in a BUG_ON(), leaving the device with MSI enabled and thus leaking its vector. +4.2.5 pci_msi_vec_count + +int pci_msi_vec_count(struct pci_dev *dev) + +This function could be used to retrieve the number of MSI vectors the +device requested (via the Multiple Message Capable register). The MSI +specification only allows the returned value to be a power of two, +up to a maximum of 2^5 (32). + +If this function returns a negative number, it indicates the device is +not capable of sending MSIs. + +If this function returns a positive number, it indicates the maximum +number of MSI interrupt vectors that could be allocated. + 4.3 Using MSI-X The MSI-X capability is much more flexible than the MSI capability. diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c index ce0d4eb91a22..ba6d0a9bdd39 100644 --- a/drivers/pci/msi.c +++ b/drivers/pci/msi.c @@ -843,6 +843,31 @@ static int pci_msi_check_device(struct pci_dev *dev, int nvec, int type) } /** + * 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); + +/** * pci_enable_msi_block - configure device's MSI capability structure * @dev: device to configure * @nvec: number of interrupts to configure @@ -858,13 +883,13 @@ static int pci_msi_check_device(struct pci_dev *dev, int nvec, int type) int pci_enable_msi_block(struct pci_dev *dev, int nvec) { int status, maxvec; - u16 msgctl; - if (!dev->msi_cap || dev->current_state != PCI_D0) + if (dev->current_state != PCI_D0) return -EINVAL; - pci_read_config_word(dev, dev->msi_cap + PCI_MSI_FLAGS, &msgctl); - maxvec = 1 << ((msgctl & PCI_MSI_FLAGS_QMASK) >> 1); + maxvec = pci_msi_vec_count(dev); + if (maxvec < 0) + return maxvec; if (nvec > maxvec) return maxvec; @@ -889,13 +914,13 @@ EXPORT_SYMBOL(pci_enable_msi_block); int pci_enable_msi_block_auto(struct pci_dev *dev, int *maxvec) { int ret, nvec; - u16 msgctl; - if (!dev->msi_cap || dev->current_state != PCI_D0) + if (dev->current_state != PCI_D0) return -EINVAL; - pci_read_config_word(dev, dev->msi_cap + PCI_MSI_FLAGS, &msgctl); - ret = 1 << ((msgctl & PCI_MSI_FLAGS_QMASK) >> 1); + ret = pci_msi_vec_count(dev); + if (ret < 0) + return ret; if (maxvec) *maxvec = ret; diff --git a/include/linux/pci.h b/include/linux/pci.h index 7c34c3913bcb..6691de093f1c 100644 --- a/include/linux/pci.h +++ b/include/linux/pci.h @@ -1154,6 +1154,11 @@ struct msix_entry { #ifndef CONFIG_PCI_MSI +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) { return -ENOSYS; @@ -1195,6 +1200,7 @@ static inline int pci_msi_enabled(void) return 0; } #else +int pci_msi_vec_count(struct pci_dev *dev); int pci_enable_msi_block(struct pci_dev *dev, int nvec); int pci_enable_msi_block_auto(struct pci_dev *dev, int *maxvec); void pci_msi_shutdown(struct pci_dev *dev); |