Re: [RFC PATCH] PCI: export MSI mode using attributes, not kobjects

Bjorn Helgaas
2013-11-01T23:40:26Z

On Tue, Oct 29, 2013 at 3:46 PM, Greg Kroah-Hartman
<gregkh@linuxfoundation.org> wrote:
> From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>
> The PCI MSI sysfs code is a mess with kobjects for things that don't
> really need to be kobjects. This patch creates attributes dynamically
> for the MSI interrupts instead of using kobjects.
>
> Note, this does not delete the existing sysfs MSI code, but puts the
> attributes under a "msi_irqs_2" directory for testing / example.
>
> Also note, this removes a directory from the current MSI interrupt sysfs
> code:
>
> old MSI kobjects:
> pci_device
> └── msi_irqs
> └── 40
> └── mode
>
> new MSI attributes:
> pci_device
> └── msi_irqs_2
> └── 40
>
> As there was only one file "mode" with the kobject model, the interrupt
> number is now a file that returns the "mode" of the interrupt (msi vs.
> msix).
>
> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> ---
>
> Bjorn, I can make up a patch that rips out the existing kobject code
> here, but I figured this patch would make things easier to follow
> instead of having to dig through the removed logic at the same time.
>
> I'll clean up the error handling path for the create attribute logic as
> well, this was just a proof of concept that this could be done.
>
> Do you think that anyone cares about the current mode files in sysfs to
> move things in this manner?

I like this a lot better than trying to fix all the holes in the
current kobject code.

I have no idea who, if anybody, cares about the "mode" files. I
assume there's a way to create the "mode" files with attributes, too?
If so, we could replicate the existing structure with one patch, and
simplify it with a second patch, so it would be easier to revert the
directory change while keeping the fix.

Bjorn

> drivers/pci/msi.c | 85 ++++++++++++++++++++++++++++++++++++++++++++++++++++
> include/linux/pci.h | 1
> 2 files changed, 86 insertions(+)
>
> diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
> index d5f90d63..53848ab9 100644
> --- a/drivers/pci/msi.c
> +++ b/drivers/pci/msi.c
> @@ -353,6 +353,9 @@ void write_msi_msg(unsigned int irq, struct msi_msg *msg)
> static void free_msi_irqs(struct pci_dev *dev)
> {
> struct msi_desc *entry, *tmp;
> + struct attribute **msi_attrs;
> + struct device_attribute *dev_attr;
> + int count = 0;
>
> list_for_each_entry(entry, &dev->msi_list, list) {
> int i, nvec;
> @@ -388,6 +391,22 @@ static void free_msi_irqs(struct pci_dev *dev)
> list_del(&entry->list);
> kfree(entry);
> }
> +
> + if (dev->msi_irq_groups) {
> + sysfs_remove_groups(&dev->dev.kobj, dev->msi_irq_groups);
> + msi_attrs = dev->msi_irq_groups[0]->attrs;
> + list_for_each_entry(entry, &dev->msi_list, list) {
> + dev_attr = container_of(msi_attrs[count],
> + struct device_attribute, attr);
> + kfree(dev_attr->attr.name);
> + kfree(dev_attr);
> + ++count;
> + }
> + kfree(msi_attrs);
> + kfree(dev->msi_irq_groups[0]);
> + kfree(dev->msi_irq_groups);
> + dev->msi_irq_groups = NULL;
> + }
> }
>
> static struct msi_desc *alloc_msi_entry(struct pci_dev *dev)
> @@ -517,13 +536,79 @@ static struct kobj_type msi_irq_ktype = {
> .default_attrs = msi_irq_default_attrs,
> };
>
> +static ssize_t msi_mode_show(struct device *dev, struct device_attribute *attr,
> + char *buf)
> +{
> + struct pci_dev *pdev = to_pci_dev(dev);
> + struct msi_desc *entry;
> + unsigned long irq;
> + int retval;
> +
> + retval = kstrtoul(attr->attr.name, 10, &irq);
> + if (retval)
> + return retval;
> +
> + list_for_each_entry(entry, &pdev->msi_list, list) {
> + if (entry->irq == irq) {
> + return sprintf(buf, "%s\n",
> + entry->msi_attrib.is_msix ? "msix" : "msi");
> + }
> + }
> + return -ENODEV;
> +}
> +
> static int populate_msi_sysfs(struct pci_dev *pdev)
> {
> + struct attribute **msi_attrs;
> + struct device_attribute *msi_dev_attr;
> + struct attribute_group *msi_irq_group;
> + const struct attribute_group **msi_irq_groups;
> struct msi_desc *entry;
> struct kobject *kobj;
> int ret;
> + int num_msi = 0;
> int count = 0;
>
> + /* Determine how many msi entries we have */
> + list_for_each_entry(entry, &pdev->msi_list, list) {
> + ++num_msi;
> + }
> + if (!num_msi)
> + return 0;
> +
> + /* Dynamically create the MSI attributes for the PCI device */
> + msi_attrs = kzalloc(sizeof(void *) * (num_msi + 1), GFP_KERNEL);
> + if (!msi_attrs)
> + return -ENOMEM;
> + list_for_each_entry(entry, &pdev->msi_list, list) {
> + char *name = kmalloc(20, GFP_KERNEL);
> + msi_dev_attr = kzalloc(sizeof(*msi_dev_attr), GFP_KERNEL);
> + if (!msi_dev_attr)
> + return -ENOMEM;
> + sprintf(name, "%d", entry->irq);
> + msi_dev_attr->attr.name = name;
> + msi_dev_attr->attr.mode = S_IRUGO;
> + msi_dev_attr->show = msi_mode_show;
> + msi_attrs[count] = &msi_dev_attr->attr;
> + ++count;
> + }
> +
> + msi_irq_group = kzalloc(sizeof(*msi_irq_group), GFP_KERNEL);
> + if (!msi_irq_group)
> + return -ENOMEM;
> + msi_irq_group->name = "msi_irqs_2";
> + msi_irq_group->attrs = msi_attrs;
> +
> + msi_irq_groups = kzalloc(sizeof(void *) * 2, GFP_KERNEL);
> + if (!msi_irq_groups)
> + return -ENOMEM;
> + msi_irq_groups[0] = msi_irq_group;
> +
> + ret = sysfs_create_groups(&pdev->dev.kobj, msi_irq_groups);
> + if (ret)
> + return ret;
> + pdev->msi_irq_groups = msi_irq_groups;
> +
> pdev->msi_kset = kset_create_and_add("msi_irqs", NULL, &pdev->dev.kobj);
> if (!pdev->msi_kset)
> return -ENOMEM;
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index da172f95..9540110f 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -354,6 +354,7 @@ struct pci_dev {
> #ifdef CONFIG_PCI_MSI
> struct list_head msi_list;
> struct kset *msi_kset;
> + const struct attribute_group **msi_irq_groups;
> #endif
> struct pci_vpd *vpd;
> #ifdef CONFIG_PCI_ATS