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Date: Tue, 17 Dec 2013 17:33:13 -0700
From: Bjorn Helgaas <bhelgaas@...gle.com>
To: Alexander Gordeev <agordeev@...hat.com>
Cc: linux-kernel@...r.kernel.org,
Michael Ellerman <michael@...erman.id.au>,
Benjamin Herrenschmidt <benh@...nel.crashing.org>,
Tejun Heo <tj@...nel.org>,
Ben Hutchings <bhutchings@...arflare.com>,
David Laight <David.Laight@...LAB.COM>,
Mark Lord <kernel@...rt.ca>, "H. Peter Anvin" <hpa@...or.com>,
linux-pci@...r.kernel.org
Subject: Re: [PATCH v4 6/9] PCI/MSI: Factor out pci_get_msi_vec_count()
interface
On Mon, Dec 16, 2013 at 09:34:59AM +0100, Alexander Gordeev wrote:
> Device drivers can use this interface to obtain maximum number
> of MSI interrupts the device supports and use that number i.e.
> in a following call to pci_enable_msi_block() interface.
>
> Signed-off-by: Alexander Gordeev <agordeev@...hat.com>
> Reviewed-by: Tejun Heo <tj@...nel.org>
> ---
> Documentation/PCI/MSI-HOWTO.txt | 15 ++++++++++++++
> drivers/pci/msi.c | 41 +++++++++++++++++++++++++++++++-------
> 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 a4d174e..c03b815 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_get_msi_vec_count
> +
> +int pci_get_msi_vec_count(struct pci_dev *dev)
What would you think of "pci_msi_vec_count()" or "pci_msi_vector_count()"
instead? The "get" doesn't really seem necessary, and we often use "get"
to indicate acquiring a reference (though it's obvious that doesn't apply
here).
Bjorn
> +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 c0e2259..8915edb 100644
> --- a/drivers/pci/msi.c
> +++ b/drivers/pci/msi.c
> @@ -834,6 +834,31 @@ static int pci_msi_check_device(struct pci_dev *dev, int nvec, int type)
> }
>
> /**
> + * pci_get_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_get_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_get_msi_vec_count);
> +
> +/**
> * pci_enable_msi_block - configure device's MSI capability structure
> * @dev: device to configure
> * @nvec: number of interrupts to configure
> @@ -849,13 +874,13 @@ 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_get_msi_vec_count(dev);
> + if (maxvec < 0)
> + return maxvec;
> if (nvec > maxvec)
> return maxvec;
>
> @@ -880,13 +905,13 @@ 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_get_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 8cf7b15..997751d 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_get_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_get_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);
> --
> 1.7.7.6
>
--
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