virtio-mmio: Devices parameter parsing

This patch adds an option to instantiate guest virtio-mmio devices
basing on a kernel command line (or module) parameter, for example:

	virtio_mmio.devices=0x100@0x100b0000:48

Signed-off-by: Pawel Moll <pawel.moll@arm.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

2 files changed, 174 insertions, 0 deletions

diff --git a/drivers/virtio/Kconfig b/drivers/virtio/Kconfig
index 1a61939b85fc..f38b17a86c35 100644
--- a/drivers/virtio/Kconfig
+++ b/drivers/virtio/Kconfig
@@ -46,4 +46,15 @@ config VIRTIO_BALLOON
 
          If unsure, say N.
 
+config VIRTIO_MMIO_CMDLINE_DEVICES
+        bool "Memory mapped virtio devices parameter parsing"
+        depends on VIRTIO_MMIO
+        ---help---
+         Allow virtio-mmio devices instantiation via the kernel command line
+         or module parameters. Be aware that using incorrect parameters (base
+         address in particular) can crash your system - you have been warned.
+         See Documentation/kernel-parameters.txt for details.
+
+         If unsure, say 'N'.
+
 endmenu
diff --git a/drivers/virtio/virtio_mmio.c b/drivers/virtio/virtio_mmio.c
index 01d6dc250d5c..453db0c403d8 100644
--- a/drivers/virtio/virtio_mmio.c
+++ b/drivers/virtio/virtio_mmio.c
@@ -6,6 +6,50 @@
  * This module allows virtio devices to be used over a virtual, memory mapped
  * platform device.
  *
+ * The guest device(s) may be instantiated in one of three equivalent ways:
+ *
+ * 1. Static platform device in board's code, eg.:
+ *
+ *      static struct platform_device v2m_virtio_device = {
+ *              .name = "virtio-mmio",
+ *              .id = -1,
+ *              .num_resources = 2,
+ *              .resource = (struct resource []) {
+ *                      {
+ *                              .start = 0x1001e000,
+ *                              .end = 0x1001e0ff,
+ *                              .flags = IORESOURCE_MEM,
+ *                      }, {
+ *                              .start = 42 + 32,
+ *                              .end = 42 + 32,
+ *                              .flags = IORESOURCE_IRQ,
+ *                      },
+ *              }
+ *      };
+ *
+ * 2. Device Tree node, eg.:
+ *
+ *              virtio_block@1e000 {
+ *                      compatible = "virtio,mmio";
+ *                      reg = <0x1e000 0x100>;
+ *                      interrupts = <42>;
+ *              }
+ *
+ * 3. Kernel module (or command line) parameter. Can be used more than once -
+ *    one device will be created for each one. Syntax:
+ *
+ *              [virtio_mmio.]device=<size>@<baseaddr>:<irq>[:<id>]
+ *    where:
+ *              <size>     := size (can use standard suffixes like K, M or G)
+ *              <baseaddr> := physical base address
+ *              <irq>      := interrupt number (as passed to request_irq())
+ *              <id>       := (optional) platform device id
+ *    eg.:
+ *              virtio_mmio.device=0x100@0x100b0000:48 \
+ *                              virtio_mmio.device=1K@0x1001e000:74
+ *
+ *
+ *
  * Registers layout (all 32-bit wide):
  *
  * offset d. name             description
@@ -42,6 +86,8 @@
  * See the COPYING file in the top-level directory.
  */
 
+#define pr_fmt(fmt) "virtio-mmio: " fmt
+
 #include <linux/highmem.h>
 #include <linux/interrupt.h>
 #include <linux/io.h>
@@ -449,6 +495,122 @@ static int __devexit virtio_mmio_remove(struct platform_device *pdev)
 
 
 
+/* Devices list parameter */
+
+#if defined(CONFIG_VIRTIO_MMIO_CMDLINE_DEVICES)
+
+static struct device vm_cmdline_parent = {
+        .init_name = "virtio-mmio-cmdline",
+};
+
+static int vm_cmdline_parent_registered;
+static int vm_cmdline_id;
+
+static int vm_cmdline_set(const char *device,
+                const struct kernel_param *kp)
+{
+        int err;
+        struct resource resources[2] = {};
+        char *str;
+        long long int base;
+        int processed, consumed = 0;
+        struct platform_device *pdev;
+
+        resources[0].flags = IORESOURCE_MEM;
+        resources[1].flags = IORESOURCE_IRQ;
+
+        resources[0].end = memparse(device, &str) - 1;
+
+        processed = sscanf(str, "@%lli:%u%n:%d%n",
+                        &base, &resources[1].start, &consumed,
+                        &vm_cmdline_id, &consumed);
+
+        if (processed < 2 || processed > 3 || str[consumed])
+                return -EINVAL;
+
+        resources[0].start = base;
+        resources[0].end += base;
+        resources[1].end = resources[1].start;
+
+        if (!vm_cmdline_parent_registered) {
+                err = device_register(&vm_cmdline_parent);
+                if (err) {
+                        pr_err("Failed to register parent device!\n");
+                        return err;
+                }
+                vm_cmdline_parent_registered = 1;
+        }
+
+        pr_info("Registering device virtio-mmio.%d at 0x%llx-0x%llx, IRQ %d.\n",
+                       vm_cmdline_id,
+                       (unsigned long long)resources[0].start,
+                       (unsigned long long)resources[0].end,
+                       (int)resources[1].start);
+
+        pdev = platform_device_register_resndata(&vm_cmdline_parent,
+                        "virtio-mmio", vm_cmdline_id++,
+                        resources, ARRAY_SIZE(resources), NULL, 0);
+        if (IS_ERR(pdev))
+                return PTR_ERR(pdev);
+
+        return 0;
+}
+
+static int vm_cmdline_get_device(struct device *dev, void *data)
+{
+        char *buffer = data;
+        unsigned int len = strlen(buffer);
+        struct platform_device *pdev = to_platform_device(dev);
+
+        snprintf(buffer + len, PAGE_SIZE - len, "0x%llx@0x%llx:%llu:%d\n",
+                        pdev->resource[0].end - pdev->resource[0].start + 1ULL,
+                        (unsigned long long)pdev->resource[0].start,
+                        (unsigned long long)pdev->resource[1].start,
+                        pdev->id);
+        return 0;
+}
+
+static int vm_cmdline_get(char *buffer, const struct kernel_param *kp)
+{
+        buffer[0] = '\0';
+        device_for_each_child(&vm_cmdline_parent, buffer,
+                        vm_cmdline_get_device);
+        return strlen(buffer) + 1;
+}
+
+static struct kernel_param_ops vm_cmdline_param_ops = {
+        .set = vm_cmdline_set,
+        .get = vm_cmdline_get,
+};
+
+device_param_cb(device, &vm_cmdline_param_ops, NULL, S_IRUSR);
+
+static int vm_unregister_cmdline_device(struct device *dev,
+                void *data)
+{
+        platform_device_unregister(to_platform_device(dev));
+
+        return 0;
+}
+
+static void vm_unregister_cmdline_devices(void)
+{
+        if (vm_cmdline_parent_registered) {
+                device_for_each_child(&vm_cmdline_parent, NULL,
+                                vm_unregister_cmdline_device);
+                device_unregister(&vm_cmdline_parent);
+                vm_cmdline_parent_registered = 0;
+        }
+}
+
+#else
+
+static void vm_unregister_cmdline_devices(void)
+{
+}
+
+#endif
+
 /* Platform driver */
 
 static struct of_device_id virtio_mmio_match[] = {
@@ -475,6 +637,7 @@ static int __init virtio_mmio_init(void)
 static void __exit virtio_mmio_exit(void)
 {
         platform_driver_unregister(&virtio_mmio_driver);
+        vm_unregister_cmdline_devices();
 }
 
 module_init(virtio_mmio_init);