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    Subject[PATCH] pci: Export pci device msi table via sysfs
    I've been working on some improvements to how we balance irqs for high volume
    interrupt sources. The consensus so far has been that what would be really
    helpful is a irqbalance mechanism that operates in a one shot mode in response
    to the addition of high volume interrupt sources (i.e. network devices mainly).
    In attempting to implement this, I've found that it would be really useful to
    have 2 bits of information:

    1) A clear correlation of which interrupts belong to which devices. Parsing
    /proc/interrupts is an exercize in guessing what naming pattern a given driver
    follows, and requires some amount of stateful information to be kept in user
    space, lest every device addition require a rebalancing of every interrupt in
    the system.

    2) A indicator as to which kind of interrupts a given device is using. The irq
    attribute for a pci device is always accurate in that it simply reads whats in
    the appropriate pci config space register, but devices using msi interrupts have
    no use for that register, and never request that interrupt number.

    This patch adds the requisite information. It creates two per-pci-device irq
    attribute files:

    a) irq_mode - identifies which kind of irqs the device in question is using,

    b) msi_table - populated only if msi(x) is enabled, it lists the irqs allocated
    to the pci device

    Using this information I can implement a stateless irq one-shot balancer that
    reacts to various udev events quite well

    Signed-off-by: Neil Horman <>
    CC: Jesse Barnes <>
    drivers/pci/pci-sysfs.c | 33 +++++++++++++++++++++++++++++++++
    1 files changed, 33 insertions(+), 0 deletions(-)

    diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
    index f8deb3e..1397dfb 100644
    --- a/drivers/pci/pci-sysfs.c
    +++ b/drivers/pci/pci-sysfs.c
    @@ -26,6 +26,7 @@
    #include <linux/security.h>
    #include <linux/pci-aspm.h>
    #include <linux/slab.h>
    +#include <linux/msi.h>
    #include "pci.h"

    static int sysfs_initialized; /* = 0 */
    @@ -71,6 +72,34 @@ static ssize_t broken_parity_status_store(struct device *dev,
    return count;

    +static ssize_t irq_mode_show(struct device *dev,
    + struct device_attribute *attr, char *buf)
    + struct pci_dev *pdev = to_pci_dev(dev);
    + return sprintf(buf, "%s\n", pdev->msix_enabled ? "msix" :
    + (pdev->msi_enabled ? "msi" : "intx"));
    +#ifdef CONFIG_PCI_MSI
    +static ssize_t msi_list_show(struct device *dev,
    + struct device_attribute *attr, char *buf)
    + struct pci_dev *pdev = to_pci_dev(dev);
    + struct msi_desc *entry;
    + int first, last;
    + ssize_t count = 0;
    + if (!(pdev->msi_enabled || pdev->msix_enabled))
    + return 0;
    + list_for_each_entry(entry, &pdev->msi_list, list)
    + count += sprintf(&buf[count], "%d ", entry->irq);
    + return count;
    static ssize_t local_cpus_show(struct device *dev,
    struct device_attribute *attr, char *buf)
    @@ -328,6 +357,10 @@ struct device_attribute pci_dev_attrs[] = {
    + __ATTR_RO(irq_mode),
    +#ifdef CONFIG_PCI_MSI
    + __ATTR_RO(msi_list),

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      Last update: 2011-04-21 21:01    [W:1.313 / U:17.972 seconds]
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