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

[Greg Kroah-Hartman]

From: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

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
   âââ msi_irqs
    ÂÂ âââ 40
    ÂÂ     âââ mode

new MSI attributes:
pci_device
   âââ msi_irqs_2
    ÂÂ âââ 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@xxxxxxxxxxxxxxxxxxx>
---

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?

 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
--
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