target/linux/layerscape/patches-5.4/701-net-0136-bus-fsl-mc-add-device-binding-path-driver_override.patch

   1 From f2991d30ff590bf932483a6dfc16c7ebe2f83341 Mon Sep 17 00:00:00 2001
   2 From: Laurentiu Tudor <laurentiu.tudor@nxp.com>
   3 Date: Fri, 13 Apr 2018 12:42:40 +0300
   4 Subject: [PATCH] bus: fsl-mc: add device binding path 'driver_override'
   5
   6 This patch is required for vfio-fsl-mc meta driver to successfully bind
   7 layerscape container devices for device passthrough. This patch adds
   8 a mechanism to allow a layerscape device to specify a driver rather than
   9 a layerscape driver provide a device match.
  10
  11 This patch is based on following proposed patches for PCI and platform
  12 devices
  13 - https://lkml.org/lkml/2014/4/8/571  :- For Platform devices
  14 - http://lists-archives.com/linux-kernel/28030441-pci-introduce-new-device-binding-path-using-pci_dev-driver_override.html
  15 :- For PCI devices
  16
  17 Example to allow a device (dprc.1) to specifically bind
  18 with driver (vfio-fsl-mc):-
  19  - echo vfio-fsl-mc > /sys/bus/fsl-mc/devices/dprc.1/driver_override
  20  - echo dprc.1 > /sys/bus/fsl-mc/drivers/fsl_mc_dprc/unbind
  21  - echo dprc.1 > /sys/bus/fsl-mc/drivers/vfio-fsl-mc/bind
  22
  23 Signed-off-by: Bharat Bhushan <Bharat.Bhushan@nxp.com>
  24 Signed-off-by: Laurentiu Tudor <laurentiu.tudor@nxp.com>
  25 ---
  26  drivers/bus/fsl-mc/fsl-mc-bus.c | 53 +++++++++++++++++++++++++++++++++++++++++
  27  1 file changed, 53 insertions(+)
  28
  29 --- a/drivers/bus/fsl-mc/fsl-mc-bus.c
  30 +++ b/drivers/bus/fsl-mc/fsl-mc-bus.c
  31 @@ -83,6 +83,12 @@ static int fsl_mc_bus_match(struct devic
  32         struct fsl_mc_driver *mc_drv = to_fsl_mc_driver(drv);
  33         bool found = false;
  34
  35 +       /* When driver_override is set, only bind to the matching driver */
  36 +       if (mc_dev->driver_override) {
  37 +               found = !strcmp(mc_dev->driver_override, mc_drv->driver.name);
  38 +               goto out;
  39 +       }
  40 +
  41         if (!mc_drv->match_id_table)
  42                 goto out;
  43
  44 @@ -147,8 +153,52 @@ static ssize_t modalias_show(struct devi
  45  }
  46  static DEVICE_ATTR_RO(modalias);
  47
  48 +static ssize_t driver_override_store(struct device *dev,
  49 +                                    struct device_attribute *attr,
  50 +                                    const char *buf, size_t count)
  51 +{
  52 +       struct fsl_mc_device *mc_dev = to_fsl_mc_device(dev);
  53 +       const char *driver_override, *old = mc_dev->driver_override;
  54 +       char *cp;
  55 +
  56 +       if (WARN_ON(dev->bus != &fsl_mc_bus_type))
  57 +               return -EINVAL;
  58 +
  59 +       if (count >= (PAGE_SIZE - 1))
  60 +               return -EINVAL;
  61 +
  62 +       driver_override = kstrndup(buf, count, GFP_KERNEL);
  63 +       if (!driver_override)
  64 +               return -ENOMEM;
  65 +
  66 +       cp = strchr(driver_override, '\n');
  67 +       if (cp)
  68 +               *cp = '\0';
  69 +
  70 +       if (strlen(driver_override)) {
  71 +               mc_dev->driver_override = driver_override;
  72 +       } else {
  73 +               kfree(driver_override);
  74 +               mc_dev->driver_override = NULL;
  75 +       }
  76 +
  77 +       kfree(old);
  78 +
  79 +       return count;
  80 +}
  81 +
  82 +static ssize_t driver_override_show(struct device *dev,
  83 +                                   struct device_attribute *attr, char *buf)
  84 +{
  85 +       struct fsl_mc_device *mc_dev = to_fsl_mc_device(dev);
  86 +
  87 +       return snprintf(buf, PAGE_SIZE, "%s\n", mc_dev->driver_override);
  88 +}
  89 +static DEVICE_ATTR_RW(driver_override);
  90 +
  91  static struct attribute *fsl_mc_dev_attrs[] = {
  92         &dev_attr_modalias.attr,
  93 +       &dev_attr_driver_override.attr,
  94         NULL,
  95  };
  96
  97 @@ -749,6 +799,9 @@ EXPORT_SYMBOL_GPL(fsl_mc_device_add);
  98   */
  99  void fsl_mc_device_remove(struct fsl_mc_device *mc_dev)
 100  {
 101 +       kfree(mc_dev->driver_override);
 102 +       mc_dev->driver_override = NULL;
 103 +
 104         /*
 105          * The device-specific remove callback will get invoked by device_del()
 106          */