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// SPDX-License-Identifier: MIT
#include <linux/fb.h>
#include <linux/vgaarb.h>
#include <drm/drm_aperture.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 int remove_conflicting_framebuffers(struct pci_dev *pdev)
* {
* bool primary = false;
* resource_size_t base, size;
* int ret;
*
* base = pci_resource_start(pdev, 0);
* size = pci_resource_len(pdev, 0);
* #ifdef CONFIG_X86
* primary = pdev->resource[PCI_ROM_RESOURCE].flags & IORESOURCE_ROM_SHADOW;
* #endif
*
* return drm_aperture_remove_conflicting_framebuffers(base, size, primary,
* "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.
*/
/**
* 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
* @primary: also kick vga16fb if present
* @name: requesting driver name
*
* This function removes graphics device drivers which use 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,
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);
return ret;
#else
return 0;
#endif
}
EXPORT_SYMBOL(drm_aperture_remove_conflicting_framebuffers);
/**
* drm_aperture_remove_conflicting_pci_framebuffers - remove existing framebuffers for PCI devices
* @pdev: PCI device
* @name: requesting driver name
*
* This function removes graphics device drivers using memory range configured
* for any of @pdev's memory bars. The function assumes that 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 char *name)
{
int ret = 0;
/*
* 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);
#endif
if (ret == 0)
ret = vga_remove_vgacon(pdev);
return ret;
}
EXPORT_SYMBOL(drm_aperture_remove_conflicting_pci_framebuffers);
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