// SPDX-License-Identifier: MIT
#include <linux/aperture.h>
#include <linux/platform_device.h>
#include <drm/drm_aperture.h>
#include <drm/drm_drv.h>
#include <drm/drm_print.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. DRM aperture functions manage
* ownership of DRM framebuffer memory and hand-over between drivers.
*
* DRM drivers should call drm_aperture_remove_conflicting_framebuffers()
* at the top of their probe function. The function removes any generic
* driver that is currently associated with the given framebuffer memory.
* If the framebuffer is located at PCI BAR 0, the rsp code looks as in the
* example given below.
*
* .. code-block:: c
*
* static const struct drm_driver example_driver = {
* ...
* };
*
* static int remove_conflicting_framebuffers(struct pci_dev *pdev)
* {
* resource_size_t base, size;
* int ret;
*
* base = pci_resource_start(pdev, 0);
* size = pci_resource_len(pdev, 0);
*
* return drm_aperture_remove_conflicting_framebuffers(base, size,
* &example_driver);
* }
*
* static int probe(struct pci_dev *pdev)
* {
* int ret;
*
* // Remove any generic drivers...
* ret = remove_conflicting_framebuffers(pdev);
* if (ret)
* return ret;
*
* // ... and initialize the hardware.
* ...
*
* drm_dev_register();
*
* return 0;
* }
*
* PCI device drivers should call
* drm_aperture_remove_conflicting_pci_framebuffers() and let it detect the
* framebuffer apertures automatically. Device drivers without knowledge of
* the framebuffer's location shall call drm_aperture_remove_framebuffers(),
* which removes all drivers for known framebuffer.
*
* 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
* given framebuffer memory. Ownership of the framebuffer memory is achieved
* by calling devm_aperture_acquire_from_firmware(). On success, the driver
* is 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 acquire_framebuffers(struct drm_device *dev, struct platform_device *pdev)
* {
* resource_size_t base, size;
*
* mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
* if (!mem)
* return -EINVAL;
* base = mem->start;
* size = resource_size(mem);
*
* return devm_acquire_aperture_from_firmware(dev, base, size);
* }
*
* static int probe(struct platform_device *pdev)
* {
* struct drm_device *dev;
* int ret;
*
* // ... Initialize the device...
* dev = devm_drm_dev_alloc();
* ...
*
* // ... and acquire ownership of the framebuffer.
* ret = acquire_framebuffers(dev, pdev);
* if (ret)
* return ret;
*
* drm_dev_register(dev, 0);
*
* return 0;
* }
*
* The generic driver is now subject to forced removal by other drivers. This
* only works for platform drivers that support hot unplug.
* When a driver calls drm_aperture_remove_conflicting_framebuffers() et al.
* for the registered framebuffer range, the aperture helpers call
* platform_device_unregister() and the generic driver unloads itself. It
* may not access the device's registers, framebuffer memory, ROM, etc
* afterwards.
*/
/**
* devm_aperture_acquire_from_firmware - Acquires ownership of a firmware framebuffer
* on behalf of a DRM driver.
* @dev: the DRM device to own the framebuffer memory
* @base: the framebuffer's byte offset in physical memory
* @size: the framebuffer size in bytes
*
* Installs the given device as the new owner of the framebuffer. The function
* expects the framebuffer to be provided by a platform device that has been
* set up by firmware. Firmware can be any generic interface, such as EFI,
* VESA, VGA, etc. If the native hardware driver takes over ownership of the
* framebuffer range, the firmware state gets lost. Aperture helpers will then
* unregister the platform device automatically. Acquired apertures are
* released automatically if the underlying device goes away.
*
* The function fails if the framebuffer range, or parts of it, is currently
* owned by another driver. To evict current owners, callers should use
* drm_aperture_remove_conflicting_framebuffers() et al. before calling this
* function. The function also fails if the given device is not a platform
* device.
*
* Returns:
* 0 on success, or a negative errno value otherwise.
*/
int devm_aperture_acquire_from_firmware(struct drm_device *dev, resource_size_t base,
resource_size_t size)
{
struct platform_device *pdev;
if (drm_WARN_ON(dev, !dev_is_platform(dev->dev)))
return -EINVAL;
pdev = to_platform_device(dev->dev);
return devm_aperture_acquire_for_platform_device(pdev, base, size);
}
EXPORT_SYMBOL(devm_aperture_acquire_from_firmware);
/**
* drm_aperture_remove_conflicting_framebuffers - remove existing framebuffers in the given range
* @base: the aperture's base address in physical memory
* @size: aperture size in bytes
* @req_driver: requesting DRM driver
*
* This function removes graphics device drivers which use the memory range described by
* @base and @size.
*
* Returns:
* 0 on success, or a negative errno code otherwise
*/
int drm_aperture_remove_conflicting_framebuffers(resource_size_t base, resource_size_t size,
const struct drm_driver *req_driver)
{
return aperture_remove_conflicting_devices(base, size, req_driver->name);
}
EXPORT_SYMBOL(drm_aperture_remove_conflicting_framebuffers);
/**
* drm_aperture_remove_conflicting_pci_framebuffers - remove existing framebuffers for PCI devices
* @pdev: PCI device
* @req_driver: requesting DRM driver
*
* This function removes graphics device drivers using the memory range configured
* for any of @pdev's memory bars. The function assumes that a PCI device with
* shadowed ROM drives a primary display and so kicks out vga16fb.
*
* Returns:
* 0 on success, or a negative errno code otherwise
*/
int drm_aperture_remove_conflicting_pci_framebuffers(struct pci_dev *pdev,
const struct drm_driver *req_driver)
{
return aperture_remove_conflicting_pci_devices(pdev, req_driver->name);
}
EXPORT_SYMBOL(drm_aperture_remove_conflicting_pci_framebuffers);
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