OSCL-LXR linux-6.0.1/​drivers/​video/​aperture.c	Source navigation Diff markup Identifier search General search
	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // SPDX-License-Identifier: MIT
 
 #include <linux/aperture.h>
 #include <linux/device.h>
 #include <linux/fb.h> /* for old fbdev helpers */
 #include <linux/list.h>
 #include <linux/mutex.h>
 #include <linux/pci.h>
 #include <linux/platform_device.h>
 #include <linux/slab.h>
 #include <linux/types.h>
 #include <linux/vgaarb.h>
 
 /**
  * DOC: overview
  *
  * A graphics device might be supported by different drivers, but only one
  * driver can be active at any given time. Many systems load a generic
  * graphics drivers, such as EFI-GOP or VESA, early during the boot process.
  * During later boot stages, they replace the generic driver with a dedicated,
  * hardware-specific driver. To take over the device the dedicated driver
  * first has to remove the generic driver. Aperture functions manage
  * ownership of framebuffer memory and hand-over between drivers.
  *
  * Graphics drivers should call aperture_remove_conflicting_devices()
  * at the top of their probe function. The function removes any generic
  * driver that is currently associated with the given framebuffer memory.
  * An example for a graphics device on the platform bus is shown below.
  *
  * .. code-block:: c
  *
  *  static int example_probe(struct platform_device *pdev)
  *  {
  *      struct resource *mem;
  *      resource_size_t base, size;
  *      int ret;
  *
  *      mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
  *      if (!mem)
  *          return -ENODEV;
  *      base = mem->start;
  *      size = resource_size(mem);
  *
  *      ret = aperture_remove_conflicting_devices(base, size, false, "example");
  *      if (ret)
  *          return ret;
  *
  *      // Initialize the hardware
  *      ...
  *
  *      return 0;
  *  }
  *
  *  static const struct platform_driver example_driver = {
  *      .probe = example_probe,
  *      ...
  *  };
  *
  * The given example reads the platform device's I/O-memory range from the
  * device instance. An active framebuffer will be located within this range.
  * The call to aperture_remove_conflicting_devices() releases drivers that
  * have previously claimed ownership of the range and are currently driving
  * output on the framebuffer. If successful, the new driver can take over
  * the device.
  *
  * While the given example uses a platform device, the aperture helpers work
  * with every bus that has an addressable framebuffer. In the case of PCI,
  * device drivers can also call aperture_remove_conflicting_pci_devices() and
  * let the function detect the apertures automatically. Device drivers without
  * knowledge of the framebuffer's location can call
  * aperture_remove_all_conflicting_devices(), which removes all known devices.
  *
  * Drivers that are susceptible to being removed by other drivers, such as
  * generic EFI or VESA drivers, have to register themselves as owners of their
  * framebuffer apertures. Ownership of the framebuffer memory is achieved
  * by calling devm_aperture_acquire_for_platform_device(). If successful, the
  * driveris the owner of the framebuffer range. The function fails if the
  * framebuffer is already owned by another driver. See below for an example.
  *
  * .. code-block:: c
  *
  *  static int generic_probe(struct platform_device *pdev)
  *  {
  *      struct resource *mem;
  *      resource_size_t base, size;
  *
  *      mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
  *      if (!mem)
  *          return -ENODEV;
  *      base = mem->start;
  *      size = resource_size(mem);
  *
  *      ret = devm_aperture_acquire_for_platform_device(pdev, base, size);
  *      if (ret)
  *          return ret;
  *
  *      // Initialize the hardware
  *      ...
  *
  *      return 0;
  *  }
  *
  *  static int generic_remove(struct platform_device *)
  *  {
  *      // Hot-unplug the device
  *      ...
  *
  *      return 0;
  *  }
  *
  *  static const struct platform_driver generic_driver = {
  *      .probe = generic_probe,
  *      .remove = generic_remove,
  *      ...
  *  };
  *
  * The similar to the previous example, the generic driver claims ownership
  * of the framebuffer memory from its probe function. This will fail if the
  * memory range, or parts of it, is already owned by another driver.
  *
  * If successful, the generic driver is now subject to forced removal by
  * another driver. This only works for platform drivers that support hot
  * unplugging. When a driver calls aperture_remove_conflicting_devices()
  * et al for the registered framebuffer range, the aperture helpers call
  * platform_device_unregister() and the generic driver unloads itself. The
  * generic driver also has to provide a remove function to make this work.
  * Once hot unplugged fro mhardware, it may not access the device's
  * registers, framebuffer memory, ROM, etc afterwards.
  */
 
 struct aperture_range {
     struct device *dev;
     resource_size_t base;
     resource_size_t size;
     struct list_head lh;
     void (*detach)(struct device *dev);
 };
 
 static LIST_HEAD(apertures);
 static DEFINE_MUTEX(apertures_lock);
 
 static bool overlap(resource_size_t base1, resource_size_t end1,
             resource_size_t base2, resource_size_t end2)
 {
     return (base1 < end2) && (end1 > base2);
 }
 
 static void devm_aperture_acquire_release(void *data)
 {
     struct aperture_range *ap = data;
     bool detached = !ap->dev;
 
     if (detached)
         return;
 
     mutex_lock(&apertures_lock);
     list_del(&ap->lh);
     mutex_unlock(&apertures_lock);
 }
 
 static int devm_aperture_acquire(struct device *dev,
                  resource_size_t base, resource_size_t size,
                  void (*detach)(struct device *))
 {
     size_t end = base + size;
     struct list_head *pos;
     struct aperture_range *ap;
 
     mutex_lock(&apertures_lock);
 
     list_for_each(pos, &apertures) {
         ap = container_of(pos, struct aperture_range, lh);
         if (overlap(base, end, ap->base, ap->base + ap->size)) {
             mutex_unlock(&apertures_lock);
             return -EBUSY;
         }
     }
 
     ap = devm_kzalloc(dev, sizeof(*ap), GFP_KERNEL);
     if (!ap) {
         mutex_unlock(&apertures_lock);
         return -ENOMEM;
     }
 
     ap->dev = dev;
     ap->base = base;
     ap->size = size;
     ap->detach = detach;
     INIT_LIST_HEAD(&ap->lh);
 
     list_add(&ap->lh, &apertures);
 
     mutex_unlock(&apertures_lock);
 
     return devm_add_action_or_reset(dev, devm_aperture_acquire_release, ap);
 }
 
 static void aperture_detach_platform_device(struct device *dev)
 {
     struct platform_device *pdev = to_platform_device(dev);
 
     /*
      * Remove the device from the device hierarchy. This is the right thing
      * to do for firmware-based DRM drivers, such as EFI, VESA or VGA. After
      * the new driver takes over the hardware, the firmware device's state
      * will be lost.
      *
      * For non-platform devices, a new callback would be required.
      *
      * If the aperture helpers ever need to handle native drivers, this call
      * would only have to unplug the DRM device, so that the hardware device
      * stays around after detachment.
      */
     platform_device_unregister(pdev);
 }
 
 /**
  * devm_aperture_acquire_for_platform_device - Acquires ownership of an aperture
  *                                             on behalf of a platform device.
  * @pdev:   the platform device to own the aperture
  * @base:   the aperture's byte offset in physical memory
  * @size:   the aperture size in bytes
  *
  * Installs the given device as the new owner of the aperture. The function
  * expects the aperture to be provided by a platform device. If another
  * driver takes over ownership of the aperture, aperture helpers will then
  * unregister the platform device automatically. All acquired apertures are
  * released automatically when the underlying device goes away.
  *
  * The function fails if the aperture, or parts of it, is currently
  * owned by another device. To evict current owners, callers should use
  * remove_conflicting_devices() et al. before calling this function.
  *
  * Returns:
  * 0 on success, or a negative errno value otherwise.
  */
 int devm_aperture_acquire_for_platform_device(struct platform_device *pdev,
                           resource_size_t base,
                           resource_size_t size)
 {
     return devm_aperture_acquire(&pdev->dev, base, size, aperture_detach_platform_device);
 }
 EXPORT_SYMBOL(devm_aperture_acquire_for_platform_device);
 
 static void aperture_detach_devices(resource_size_t base, resource_size_t size)
 {
     resource_size_t end = base + size;
     struct list_head *pos, *n;
 
     mutex_lock(&apertures_lock);
 
     list_for_each_safe(pos, n, &apertures) {
         struct aperture_range *ap = container_of(pos, struct aperture_range, lh);
         struct device *dev = ap->dev;
 
         if (WARN_ON_ONCE(!dev))
             continue;
 
         if (!overlap(base, end, ap->base, ap->base + ap->size))
             continue;
 
         ap->dev = NULL; /* detach from device */
         list_del(&ap->lh);
 
         ap->detach(dev);
     }
 
     mutex_unlock(&apertures_lock);
 }
 
 /**
  * aperture_remove_conflicting_devices - remove devices in the given range
  * @base: the aperture's base address in physical memory
  * @size: aperture size in bytes
  * @primary: also kick vga16fb if present; only relevant for VGA devices
  * @name: a descriptive name of the requesting driver
  *
  * This function removes devices that own apertures within @base and @size.
  *
  * Returns:
  * 0 on success, or a negative errno code otherwise
  */
 int aperture_remove_conflicting_devices(resource_size_t base, resource_size_t size,
                     bool primary, const char *name)
 {
 #if IS_REACHABLE(CONFIG_FB)
     struct apertures_struct *a;
     int ret;
 
     a = alloc_apertures(1);
     if (!a)
         return -ENOMEM;
 
     a->ranges[0].base = base;
     a->ranges[0].size = size;
 
     ret = remove_conflicting_framebuffers(a, name, primary);
     kfree(a);
 
     if (ret)
         return ret;
 #endif
 
     aperture_detach_devices(base, size);
 
     return 0;
 }
 EXPORT_SYMBOL(aperture_remove_conflicting_devices);
 
 /**
  * aperture_remove_conflicting_pci_devices - remove existing framebuffers for PCI devices
  * @pdev: PCI device
  * @name: a descriptive name of the requesting driver
  *
  * This function removes devices that own apertures within any of @pdev's
  * memory bars. The function assumes that PCI device with shadowed ROM
  * drives a primary display and therefore kicks out vga16fb as well.
  *
  * Returns:
  * 0 on success, or a negative errno code otherwise
  */
 int aperture_remove_conflicting_pci_devices(struct pci_dev *pdev, const char *name)
 {
     resource_size_t base, size;
     int bar, ret;
 
     /*
      * WARNING: Apparently we must kick fbdev drivers before vgacon,
      * otherwise the vga fbdev driver falls over.
      */
 #if IS_REACHABLE(CONFIG_FB)
     ret = remove_conflicting_pci_framebuffers(pdev, name);
     if (ret)
         return ret;
 #endif
     ret = vga_remove_vgacon(pdev);
     if (ret)
         return ret;
 
     for (bar = 0; bar < PCI_STD_NUM_BARS; ++bar) {
         if (!(pci_resource_flags(pdev, bar) & IORESOURCE_MEM))
             continue;
         base = pci_resource_start(pdev, bar);
         size = pci_resource_len(pdev, bar);
         aperture_detach_devices(base, size);
     }
 
     return 0;
 
 }
 EXPORT_SYMBOL(aperture_remove_conflicting_pci_devices);

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