On Tue, Nov 26, 2013 at 10:09:59AM +0100, Alexander Gordeev wrote:
> Make pci_msix_table_size() function to return a negative errno
> if device does not support MSI-X interrupts. After this update
> pci_msix_table_size() can fail and callers must always check
> the returned value.
>
> This update is needed to create a consistent MSI-X counterpart
> for pci_get_msi_cap() MSI interface. Device drivers can use this
> function to obtain maximum number of MSI-X interrupts the device
> supports and i.e. use that number in a following call to
> pci_enable_msix() interface.
If pci_msix_table_size() is a counterpart to pci_get_msi_cap(), can we make
the names similar?
> The only user of pci_msix_table_size() function is PCI-Express
> port driver, which is also updated by this change.
>
> Signed-off-by: Alexander Gordeev <agordeev@xxxxxxxxxx>
> Reviewed-by: Tejun Heo <tj@xxxxxxxxxx>
> ---
> Documentation/PCI/MSI-HOWTO.txt | 13 +++++++++++++
> drivers/pci/msi.c | 12 ++++++++++--
> drivers/pci/pcie/portdrv_core.c | 5 +++--
> include/linux/pci.h | 2 +-
> 4 files changed, 27 insertions(+), 5 deletions(-)
>
> diff --git a/Documentation/PCI/MSI-HOWTO.txt b/Documentation/PCI/MSI-HOWTO.txt
> index 1fe4900..5955389 100644
> --- a/Documentation/PCI/MSI-HOWTO.txt
> +++ b/Documentation/PCI/MSI-HOWTO.txt
> @@ -243,6 +243,19 @@ MSI-X Table. This address is mapped by the PCI subsystem, and should not
> be accessed directly by the device driver. If the driver wishes to
> mask or unmask an interrupt, it should call disable_irq() / enable_irq().
>
> +4.3.4 pci_msix_table_size
> +
> +int pci_msix_table_size(struct pci_dev *dev)
> +
> +This function could be used to retrieve number of entries in the device
> +MSI-X table.
> +
> +If this function returns a negative number, it indicates the device is
> +not capable of sending MSI-Xs.
> +
> +If this function returns a positive number, it indicates the maximum
> +number of MSI-X interrupt vectors that could be allocated.
> +
> 4.4 Handling devices implementing both MSI and MSI-X capabilities
>
> If a device implements both MSI and MSI-X capabilities, it can
> diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
> index e4b02ac..6fe0add 100644
> --- a/drivers/pci/msi.c
> +++ b/drivers/pci/msi.c
> @@ -932,17 +932,23 @@ EXPORT_SYMBOL(pci_disable_msi);
> /**
> * pci_msix_table_size - return the number of device's MSI-X table entries
> * @dev: pointer to the pci_dev data structure of MSI-X device function
> - */
> +
> + * This function returns the number of device's MSI-X table entries and
> + * therefore the number of MSI-X vectors device is capable to send.
> + * It returns a negative errno if the device is not capable sending MSI-X
> + * interrupts.
> + **/
> int pci_msix_table_size(struct pci_dev *dev)
> {
> u16 control;
>
> if (!dev->msix_cap)
> - return 0;
> + return -EINVAL;
>
> pci_read_config_word(dev, dev->msix_cap + PCI_MSIX_FLAGS, &control);
> return msix_table_size(control);
> }
> +EXPORT_SYMBOL(pci_msix_table_size);
>
> /**
> * pci_enable_msix - configure device's MSI-X capability structure
> @@ -972,6 +978,8 @@ int pci_enable_msix(struct pci_dev *dev, struct msix_entry *entries, int nvec)
> return status;
>
> nr_entries = pci_msix_table_size(dev);
> + if (nr_entries < 0)
> + return nr_entries;
> if (nvec > nr_entries)
> return nr_entries;
>
> diff --git a/drivers/pci/pcie/portdrv_core.c b/drivers/pci/pcie/portdrv_core.c
> index 08d131f..5bebeec 100644
> --- a/drivers/pci/pcie/portdrv_core.c
> +++ b/drivers/pci/pcie/portdrv_core.c
> @@ -80,8 +80,9 @@ static int pcie_port_enable_msix(struct pci_dev *dev, int *vectors, int mask)
> u32 reg32;
>
> nr_entries = pci_msix_table_size(dev);
> - if (!nr_entries)
> - return -EINVAL;
> + if (nr_entries < 0)
> + return nr_entries;
> + BUG_ON(!nr_entries);
> if (nr_entries > PCIE_PORT_MAX_MSIX_ENTRIES)
> nr_entries = PCIE_PORT_MAX_MSIX_ENTRIES;
>
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 9ab1692..8af1217 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -1172,7 +1172,7 @@ static inline void pci_disable_msi(struct pci_dev *dev)
>
> static inline int pci_msix_table_size(struct pci_dev *dev)
> {
> - return 0;
> + return -ENOSYS;
> }
> static inline int pci_enable_msix(struct pci_dev *dev,
> struct msix_entry *entries, int nvec)
> --
> 1.7.7.6
>
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