Add MSI-X support and update driver documentation accordingly.

Add 2 new IOCTL commands:
 - Allow to reconfigure driver IRQ type in runtime.
 - Allow to retrieve current driver IRQ type configured.

Signed-off-by: Gustavo Pimentel <redacted>
---
Change v2->v3:
 - New patch file created base on the previous patch
"misc: pci_endpoint_test: Add MSI-X support" patch file following
Kishon's suggestion.
Change v3->v4:
 - Rebased to Lorenzo's master branch v4.18-rc1.

 Documentation/misc-devices/pci-endpoint-test.txt |   3 +
 drivers/misc/pci_endpoint_test.c                 | 177 +++++++++++++++++------
 2 files changed, 132 insertions(+), 48 deletions(-)

diff --git a/Documentation/misc-devices/pci-endpoint-test.txt b/Documentation/misc-devices/pci-endpoint-test.txt
index fdfa0f6..58ccca4 100644
--- a/Documentation/misc-devices/pci-endpoint-test.txt
+++ b/Documentation/misc-devices/pci-endpoint-test.txt

@@ -28,6 +28,9 @@ ioctl
 	      to be tested should be passed as argument.
  PCITEST_MSIX: Tests message signalled interrupts. The MSI-X number
 	      to be tested should be passed as argument.
+ PCITEST_SET_IRQTYPE: Changes driver IRQ type configuration. The IRQ type
+	      should be passed as argument (0: Legacy, 1:MSI, 2:MSI-X).
+ PCITEST_GET_IRQTYPE: Gets driver IRQ type configuration.
  PCITEST_WRITE: Perform write tests. The size of the buffer should be passed
 		as argument.
  PCITEST_READ: Perform read tests. The size of the buffer should be passed

diff --git a/drivers/misc/pci_endpoint_test.c b/drivers/misc/pci_endpoint_test.c
index 8d15dbe..df2017f 100644
--- a/drivers/misc/pci_endpoint_test.c
+++ b/drivers/misc/pci_endpoint_test.c

@@ -157,6 +157,87 @@ static irqreturn_t pci_endpoint_test_irqhandler(int irq, void *dev_id)
 	return IRQ_HANDLED;
 }
 
+static void pci_endpoint_test_free_irq_vectors(struct pci_endpoint_test *test)
+{
+	int i;
+	struct pci_dev *pdev = test->pdev;
+	struct device *dev = &pdev->dev;
+
+	for (i = 0; i < test->num_irqs; i++)
+		devm_free_irq(dev, pci_irq_vector(pdev, i), test);
+
+	test->num_irqs = 0;
+}
+
+static bool pci_endpoint_test_alloc_irq_vectors(struct pci_endpoint_test *test)
+{
+	int irq = -1;
+	struct pci_dev *pdev = test->pdev;
+	struct device *dev = &pdev->dev;
+	bool res = true;
+
+	switch (irq_type) {
+	case IRQ_TYPE_LEGACY:
+		irq = 0;
+		break;
+	case IRQ_TYPE_MSI:
+		irq = pci_alloc_irq_vectors(pdev, 1, 32, PCI_IRQ_MSI);
+		if (irq < 0)
+			dev_err(dev, "Failed to get MSI interrupts\n");
+		break;
+	case IRQ_TYPE_MSIX:
+		irq = pci_alloc_irq_vectors(pdev, 1, 2048, PCI_IRQ_MSIX);
+		if (irq < 0)
+			dev_err(dev, "Failed to get MSI-X interrupts\n");
+		break;
+	default:
+		dev_err(dev, "Invalid IRQ type selected\n");
+	}
+
+	if (irq < 0) {
+		irq = 0;
+		res = false;
+	}
+	test->num_irqs = irq;
+
+	return res;
+}
+
+static void pci_endpoint_test_release_irq(struct pci_endpoint_test *test)
+{
+	struct pci_dev *pdev = test->pdev;
+
+	pci_disable_msi(pdev);
+	pci_disable_msix(pdev);
+}
+
+static bool pci_endpoint_test_request_irq(struct pci_endpoint_test *test)
+{
+	int i;
+	int err;
+	struct pci_dev *pdev = test->pdev;
+	struct device *dev = &pdev->dev;
+
+	err = devm_request_irq(dev, pdev->irq, pci_endpoint_test_irqhandler,
+			       IRQF_SHARED, DRV_MODULE_NAME, test);
+	if (err) {
+		dev_err(dev, "Failed to request IRQ %d\n", pdev->irq);
+		return false;
+	}
+
+	for (i = 1; i < test->num_irqs; i++) {
+		err = devm_request_irq(dev, pci_irq_vector(pdev, i),
+				       pci_endpoint_test_irqhandler,
+				       IRQF_SHARED, DRV_MODULE_NAME, test);
+		if (err)
+			dev_err(dev, "Failed to request IRQ %d for MSI%s %d\n",
+				pci_irq_vector(pdev, i),
+				irq_type == IRQ_TYPE_MSIX ? "-X" : "", i + 1);
+	}
+
+	return true;
+}
+
 static bool pci_endpoint_test_bar(struct pci_endpoint_test *test,
 				  enum pci_barno barno)
 {

@@ -440,6 +521,38 @@ static bool pci_endpoint_test_read(struct pci_endpoint_test *test, size_t size)
 	return ret;
 }
 
+static bool pci_endpoint_test_set_irq(struct pci_endpoint_test *test,
+				      int req_irq_type)
+{
+	struct pci_dev *pdev = test->pdev;
+	struct device *dev = &pdev->dev;
+
+	if (req_irq_type < IRQ_TYPE_LEGACY || req_irq_type > IRQ_TYPE_MSIX) {
+		dev_err(dev, "Invalid IRQ type option\n");
+		return false;
+	}
+
+	if (irq_type == req_irq_type)
+		return true;
+
+	irq_type = req_irq_type;
+
+	pci_endpoint_test_free_irq_vectors(test);
+	pci_endpoint_test_release_irq(test);
+
+	if (!pci_endpoint_test_alloc_irq_vectors(test)) {
+		pci_endpoint_test_release_irq(test);
+		return false;
+	}
+
+	if (!pci_endpoint_test_request_irq(test)) {
+		pci_endpoint_test_release_irq(test);
+		return false;
+	}
+
+	return true;
+}
+
 static long pci_endpoint_test_ioctl(struct file *file, unsigned int cmd,
 				    unsigned long arg)
 {

@@ -471,6 +584,12 @@ static long pci_endpoint_test_ioctl(struct file *file, unsigned int cmd,
 	case PCITEST_COPY:
 		ret = pci_endpoint_test_copy(test, arg);
 		break;
+	case PCITEST_SET_IRQTYPE:
+		ret = pci_endpoint_test_set_irq(test, arg);
+		break;
+	case PCITEST_GET_IRQTYPE:
+		ret = irq_type;