// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright 2018 Noralf Trønnes
 */

#include <linux/dma-buf.h>
#include <linux/export.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/shmem_fs.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>

#ifdef CONFIG_X86
#include <asm/set_memory.h>
#endif

#include <kunit/visibility.h>

#include <drm/drm.h>
#include <drm/drm_device.h>
#include <drm/drm_drv.h>
#include <drm/drm_dumb_buffers.h>
#include <drm/drm_gem_shmem_helper.h>
#include <drm/drm_prime.h>
#include <drm/drm_print.h>

MODULE_IMPORT_NS("DMA_BUF");

/**
 * DOC: overview
 *
 * This library provides helpers for GEM objects backed by shmem buffers
 * allocated using anonymous pageable memory.
 *
 * Functions that operate on the GEM object receive struct &drm_gem_shmem_object.
 * For GEM callback helpers in struct &drm_gem_object functions, see likewise
 * named functions with an _object_ infix (e.g., drm_gem_shmem_object_vmap() wraps
 * drm_gem_shmem_vmap()). These helpers perform the necessary type conversion.
 */

static const struct drm_gem_object_funcs drm_gem_shmem_funcs = {
        .free = drm_gem_shmem_object_free,
        .print_info = drm_gem_shmem_object_print_info,
        .pin = drm_gem_shmem_object_pin,
        .unpin = drm_gem_shmem_object_unpin,
        .get_sg_table = drm_gem_shmem_object_get_sg_table,
        .vmap = drm_gem_shmem_object_vmap,
        .vunmap = drm_gem_shmem_object_vunmap,
        .mmap = drm_gem_shmem_object_mmap,
        .vm_ops = &drm_gem_shmem_vm_ops,
};

static int __drm_gem_shmem_init(struct drm_device *dev, struct drm_gem_shmem_object *shmem,
                                size_t size, bool private)
{
        struct drm_gem_object *obj = &shmem->base;
        int ret = 0;

        if (!obj->funcs)
                obj->funcs = &drm_gem_shmem_funcs;

        if (private) {
                drm_gem_private_object_init(dev, obj, size);
                shmem->map_wc = false; /* dma-buf mappings use always writecombine */
        } else {
                ret = drm_gem_object_init(dev, obj, size);
        }
        if (ret) {
                drm_gem_private_object_fini(obj);
                return ret;
        }

        ret = drm_gem_create_mmap_offset(obj);
        if (ret)
                goto err_release;

        INIT_LIST_HEAD(&shmem->madv_list);

        if (!private) {
                /*
                 * Our buffers are kept pinned, so allocating them
                 * from the MOVABLE zone is a really bad idea, and
                 * conflicts with CMA. See comments above new_inode()
                 * why this is required _and_ expected if you're
                 * going to pin these pages.
                 */
                mapping_set_gfp_mask(obj->filp->f_mapping, GFP_HIGHUSER |
                                     __GFP_RETRY_MAYFAIL | __GFP_NOWARN);
        }

        return 0;
err_release:
        drm_gem_object_release(obj);
        return ret;
}

/**
 * drm_gem_shmem_init - Initialize an allocated object.
 * @dev: DRM device
 * @shmem: shmem GEM object to initialize
 * @size: Buffer size in bytes
 *
 * This function initializes an allocated shmem GEM object.
 *
 * Returns:
 * 0 on success, or a negative error code on failure.
 */
int drm_gem_shmem_init(struct drm_device *dev, struct drm_gem_shmem_object *shmem, size_t size)
{
        return __drm_gem_shmem_init(dev, shmem, size, false);
}
EXPORT_SYMBOL_GPL(drm_gem_shmem_init);

static struct drm_gem_shmem_object *
__drm_gem_shmem_create(struct drm_device *dev, size_t size, bool private)
{
        struct drm_gem_shmem_object *shmem;
        struct drm_gem_object *obj;
        int ret = 0;

        size = PAGE_ALIGN(size);

        if (dev->driver->gem_create_object) {
                obj = dev->driver->gem_create_object(dev, size);
                if (IS_ERR(obj))
                        return ERR_CAST(obj);
                shmem = to_drm_gem_shmem_obj(obj);
        } else {
                shmem = kzalloc_obj(*shmem);
                if (!shmem)
                        return ERR_PTR(-ENOMEM);
                obj = &shmem->base;
        }

        ret = __drm_gem_shmem_init(dev, shmem, size, private);
        if (ret) {
                kfree(obj);
                return ERR_PTR(ret);
        }

        return shmem;
}
/**
 * drm_gem_shmem_create - Allocate an object with the given size
 * @dev: DRM device
 * @size: Size of the object to allocate
 *
 * This function creates a shmem GEM object.
 *
 * Returns:
 * A struct drm_gem_shmem_object * on success or an ERR_PTR()-encoded negative
 * error code on failure.
 */
struct drm_gem_shmem_object *drm_gem_shmem_create(struct drm_device *dev, size_t size)
{
        return __drm_gem_shmem_create(dev, size, false);
}
EXPORT_SYMBOL_GPL(drm_gem_shmem_create);

/**
 * drm_gem_shmem_release - Release resources associated with a shmem GEM object.
 * @shmem: shmem GEM object
 *
 * This function cleans up the GEM object state, but does not free the memory used to store the
 * object itself. This function is meant to be a dedicated helper for the Rust GEM bindings.
 */
void drm_gem_shmem_release(struct drm_gem_shmem_object *shmem)
{
        struct drm_gem_object *obj = &shmem->base;

        if (drm_gem_is_imported(obj)) {
                drm_prime_gem_destroy(obj, shmem->sgt);
        } else {
                dma_resv_lock(shmem->base.resv, NULL);

                drm_WARN_ON(obj->dev, refcount_read(&shmem->vmap_use_count));

                if (shmem->sgt) {
                        dma_unmap_sgtable(obj->dev->dev, shmem->sgt,
                                          DMA_BIDIRECTIONAL, 0);
                        sg_free_table(shmem->sgt);
                        kfree(shmem->sgt);
                }
                if (shmem->pages)
                        drm_gem_shmem_put_pages_locked(shmem);

                drm_WARN_ON(obj->dev, refcount_read(&shmem->pages_use_count));
                drm_WARN_ON(obj->dev, refcount_read(&shmem->pages_pin_count));

                dma_resv_unlock(shmem->base.resv);
        }

        drm_gem_object_release(obj);
}
EXPORT_SYMBOL_GPL(drm_gem_shmem_release);

/**
 * drm_gem_shmem_free - Free resources associated with a shmem GEM object
 * @shmem: shmem GEM object to free
 *
 * This function cleans up the GEM object state and frees the memory used to
 * store the object itself.
 */
void drm_gem_shmem_free(struct drm_gem_shmem_object *shmem)
{
        drm_gem_shmem_release(shmem);
        kfree(shmem);
}
EXPORT_SYMBOL_GPL(drm_gem_shmem_free);

static int drm_gem_shmem_get_pages_locked(struct drm_gem_shmem_object *shmem)
{
        struct drm_gem_object *obj = &shmem->base;
        struct page **pages;

        dma_resv_assert_held(shmem->base.resv);

        if (refcount_inc_not_zero(&shmem->pages_use_count))
                return 0;

        pages = drm_gem_get_pages(obj);
        if (IS_ERR(pages)) {
                drm_dbg_kms(obj->dev, "Failed to get pages (%ld)\n",
                            PTR_ERR(pages));
                return PTR_ERR(pages);
        }

        /*
         * TODO: Allocating WC pages which are correctly flushed is only
         * supported on x86. Ideal solution would be a GFP_WC flag, which also
         * ttm_pool.c could use.
         */
#ifdef CONFIG_X86
        if (shmem->map_wc)
                set_pages_array_wc(pages, obj->size >> PAGE_SHIFT);
#endif

        shmem->pages = pages;

        refcount_set(&shmem->pages_use_count, 1);

        return 0;
}

/*
 * drm_gem_shmem_put_pages_locked - Decrease use count on the backing pages for a shmem GEM object
 * @shmem: shmem GEM object
 *
 * This function decreases the use count and puts the backing pages when use drops to zero.
 */
void drm_gem_shmem_put_pages_locked(struct drm_gem_shmem_object *shmem)
{
        struct drm_gem_object *obj = &shmem->base;

        dma_resv_assert_held(shmem->base.resv);

        if (refcount_dec_and_test(&shmem->pages_use_count)) {
#ifdef CONFIG_X86
                if (shmem->map_wc)
                        set_pages_array_wb(shmem->pages, obj->size >> PAGE_SHIFT);
#endif

                drm_gem_put_pages(obj, shmem->pages,
                                  shmem->pages_mark_dirty_on_put,
                                  shmem->pages_mark_accessed_on_put);
                shmem->pages = NULL;
        }
}
EXPORT_SYMBOL_GPL(drm_gem_shmem_put_pages_locked);

int drm_gem_shmem_pin_locked(struct drm_gem_shmem_object *shmem)
{
        int ret;

        dma_resv_assert_held(shmem->base.resv);

        drm_WARN_ON(shmem->base.dev, drm_gem_is_imported(&shmem->base));

        if (refcount_inc_not_zero(&shmem->pages_pin_count))
                return 0;

        ret = drm_gem_shmem_get_pages_locked(shmem);
        if (!ret)
                refcount_set(&shmem->pages_pin_count, 1);

        return ret;
}
EXPORT_SYMBOL(drm_gem_shmem_pin_locked);

void drm_gem_shmem_unpin_locked(struct drm_gem_shmem_object *shmem)
{
        dma_resv_assert_held(shmem->base.resv);

        if (refcount_dec_and_test(&shmem->pages_pin_count))
                drm_gem_shmem_put_pages_locked(shmem);
}
EXPORT_SYMBOL(drm_gem_shmem_unpin_locked);

/**
 * drm_gem_shmem_pin - Pin backing pages for a shmem GEM object
 * @shmem: shmem GEM object
 *
 * This function makes sure the backing pages are pinned in memory while the
 * buffer is exported.
 *
 * Returns:
 * 0 on success or a negative error code on failure.
 */
int drm_gem_shmem_pin(struct drm_gem_shmem_object *shmem)
{
        struct drm_gem_object *obj = &shmem->base;
        int ret;

        drm_WARN_ON(obj->dev, drm_gem_is_imported(obj));

        if (refcount_inc_not_zero(&shmem->pages_pin_count))
                return 0;

        ret = dma_resv_lock_interruptible(shmem->base.resv, NULL);
        if (ret)
                return ret;
        ret = drm_gem_shmem_pin_locked(shmem);
        dma_resv_unlock(shmem->base.resv);

        return ret;
}
EXPORT_SYMBOL_GPL(drm_gem_shmem_pin);

/**
 * drm_gem_shmem_unpin - Unpin backing pages for a shmem GEM object
 * @shmem: shmem GEM object
 *
 * This function removes the requirement that the backing pages are pinned in
 * memory.
 */
void drm_gem_shmem_unpin(struct drm_gem_shmem_object *shmem)
{
        struct drm_gem_object *obj = &shmem->base;

        drm_WARN_ON(obj->dev, drm_gem_is_imported(obj));

        if (refcount_dec_not_one(&shmem->pages_pin_count))
                return;

        dma_resv_lock(shmem->base.resv, NULL);
        drm_gem_shmem_unpin_locked(shmem);
        dma_resv_unlock(shmem->base.resv);
}
EXPORT_SYMBOL_GPL(drm_gem_shmem_unpin);

/*
 * drm_gem_shmem_vmap_locked - Create a virtual mapping for a shmem GEM object
 * @shmem: shmem GEM object
 * @map: Returns the kernel virtual address of the SHMEM GEM object's backing
 *       store.
 *
 * This function makes sure that a contiguous kernel virtual address mapping
 * exists for the buffer backing the shmem GEM object. It hides the differences
 * between dma-buf imported and natively allocated objects.
 *
 * Acquired mappings should be cleaned up by calling drm_gem_shmem_vunmap_locked().
 *
 * Returns:
 * 0 on success or a negative error code on failure.
 */
int drm_gem_shmem_vmap_locked(struct drm_gem_shmem_object *shmem,
                              struct iosys_map *map)
{
        struct drm_gem_object *obj = &shmem->base;
        int ret = 0;

        dma_resv_assert_held(obj->resv);

        if (drm_gem_is_imported(obj)) {
                ret = dma_buf_vmap(obj->import_attach->dmabuf, map);
        } else {
                pgprot_t prot = PAGE_KERNEL;

                dma_resv_assert_held(shmem->base.resv);

                if (refcount_inc_not_zero(&shmem->vmap_use_count)) {
                        iosys_map_set_vaddr(map, shmem->vaddr);
                        return 0;
                }

                ret = drm_gem_shmem_pin_locked(shmem);
                if (ret)
                        return ret;

                if (shmem->map_wc)
                        prot = pgprot_writecombine(prot);
                shmem->vaddr = vmap(shmem->pages, obj->size >> PAGE_SHIFT,
                                    VM_MAP, prot);
                if (!shmem->vaddr) {
                        ret = -ENOMEM;
                } else {
                        iosys_map_set_vaddr(map, shmem->vaddr);
                        refcount_set(&shmem->vmap_use_count, 1);
                }
        }

        if (ret) {
                drm_dbg_kms(obj->dev, "Failed to vmap pages, error %d\n", ret);
                goto err_put_pages;
        }

        return 0;

err_put_pages:
        if (!drm_gem_is_imported(obj))
                drm_gem_shmem_unpin_locked(shmem);

        return ret;
}
EXPORT_SYMBOL_GPL(drm_gem_shmem_vmap_locked);

/*
 * drm_gem_shmem_vunmap_locked - Unmap a virtual mapping for a shmem GEM object
 * @shmem: shmem GEM object
 * @map: Kernel virtual address where the SHMEM GEM object was mapped
 *
 * This function cleans up a kernel virtual address mapping acquired by
 * drm_gem_shmem_vmap_locked(). The mapping is only removed when the use count
 * drops to zero.
 *
 * This function hides the differences between dma-buf imported and natively
 * allocated objects.
 */
void drm_gem_shmem_vunmap_locked(struct drm_gem_shmem_object *shmem,
                                 struct iosys_map *map)
{
        struct drm_gem_object *obj = &shmem->base;

        dma_resv_assert_held(obj->resv);

        if (drm_gem_is_imported(obj)) {
                dma_buf_vunmap(obj->import_attach->dmabuf, map);
        } else {
                dma_resv_assert_held(shmem->base.resv);

                if (refcount_dec_and_test(&shmem->vmap_use_count)) {
                        vunmap(shmem->vaddr);
                        shmem->vaddr = NULL;

                        drm_gem_shmem_unpin_locked(shmem);
                }
        }
}
EXPORT_SYMBOL_GPL(drm_gem_shmem_vunmap_locked);

static int
drm_gem_shmem_create_with_handle(struct drm_file *file_priv,
                                 struct drm_device *dev, size_t size,
                                 uint32_t *handle)
{
        struct drm_gem_shmem_object *shmem;
        int ret;

        shmem = drm_gem_shmem_create(dev, size);
        if (IS_ERR(shmem))
                return PTR_ERR(shmem);

        /*
         * Allocate an id of idr table where the obj is registered
         * and handle has the id what user can see.
         */
        ret = drm_gem_handle_create(file_priv, &shmem->base, handle);
        /* drop reference from allocate - handle holds it now. */
        drm_gem_object_put(&shmem->base);

        return ret;
}

/* Update madvise status, returns true if not purged, else
 * false or -errno.
 */
int drm_gem_shmem_madvise_locked(struct drm_gem_shmem_object *shmem, int madv)
{
        dma_resv_assert_held(shmem->base.resv);

        if (shmem->madv >= 0)
                shmem->madv = madv;

        madv = shmem->madv;

        return (madv >= 0);
}
EXPORT_SYMBOL_GPL(drm_gem_shmem_madvise_locked);

void drm_gem_shmem_purge_locked(struct drm_gem_shmem_object *shmem)
{
        struct drm_gem_object *obj = &shmem->base;
        struct drm_device *dev = obj->dev;

        dma_resv_assert_held(shmem->base.resv);

        drm_WARN_ON(obj->dev, !drm_gem_shmem_is_purgeable(shmem));

        dma_unmap_sgtable(dev->dev, shmem->sgt, DMA_BIDIRECTIONAL, 0);
        sg_free_table(shmem->sgt);
        kfree(shmem->sgt);
        shmem->sgt = NULL;

        drm_gem_shmem_put_pages_locked(shmem);

        shmem->madv = -1;

        drm_vma_node_unmap(&obj->vma_node, dev->anon_inode->i_mapping);
        drm_gem_free_mmap_offset(obj);

        /* Our goal here is to return as much of the memory as
         * is possible back to the system as we are called from OOM.
         * To do this we must instruct the shmfs to drop all of its
         * backing pages, *now*.
         */
        shmem_truncate_range(file_inode(obj->filp), 0, (loff_t)-1);

        invalidate_mapping_pages(file_inode(obj->filp)->i_mapping, 0, (loff_t)-1);
}
EXPORT_SYMBOL_GPL(drm_gem_shmem_purge_locked);

/**
 * drm_gem_shmem_dumb_create - Create a dumb shmem buffer object
 * @file: DRM file structure to create the dumb buffer for
 * @dev: DRM device
 * @args: IOCTL data
 *
 * This function computes the pitch of the dumb buffer and rounds it up to an
 * integer number of bytes per pixel. Drivers for hardware that doesn't have
 * any additional restrictions on the pitch can directly use this function as
 * their &drm_driver.dumb_create callback.
 *
 * For hardware with additional restrictions, drivers can adjust the fields
 * set up by userspace before calling into this function.
 *
 * Returns:
 * 0 on success or a negative error code on failure.
 */
int drm_gem_shmem_dumb_create(struct drm_file *file, struct drm_device *dev,
                              struct drm_mode_create_dumb *args)
{
        int ret;

        ret = drm_mode_size_dumb(dev, args, 0, 0);
        if (ret)
                return ret;

        return drm_gem_shmem_create_with_handle(file, dev, args->size, &args->handle);
}
EXPORT_SYMBOL_GPL(drm_gem_shmem_dumb_create);

static vm_fault_t try_insert_pfn(struct vm_fault *vmf, unsigned int order,
                                 unsigned long pfn)
{
        if (!order) {
                return vmf_insert_pfn(vmf->vma, vmf->address, pfn);
#ifdef CONFIG_ARCH_SUPPORTS_PMD_PFNMAP
        } else if (order == PMD_ORDER) {
                unsigned long paddr = pfn << PAGE_SHIFT;
                bool aligned = (vmf->address & ~PMD_MASK) == (paddr & ~PMD_MASK);

                if (aligned &&
                    folio_test_pmd_mappable(page_folio(pfn_to_page(pfn)))) {
                        pfn &= PMD_MASK >> PAGE_SHIFT;
                        return vmf_insert_pfn_pmd(vmf, pfn, false);
                }
#endif
        }
        return VM_FAULT_FALLBACK;
}

static vm_fault_t drm_gem_shmem_any_fault(struct vm_fault *vmf, unsigned int order)
{
        struct vm_area_struct *vma = vmf->vma;
        struct drm_gem_object *obj = vma->vm_private_data;
        struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
        loff_t num_pages = obj->size >> PAGE_SHIFT;
        vm_fault_t ret;
        struct page **pages = shmem->pages;
        pgoff_t page_offset;
        unsigned long pfn;

        if (order && order != PMD_ORDER)
                return VM_FAULT_FALLBACK;

        /* Offset to faulty address in the VMA. */
        page_offset = vmf->pgoff - vma->vm_pgoff;

        dma_resv_lock(shmem->base.resv, NULL);

        if (page_offset >= num_pages ||
            drm_WARN_ON_ONCE(obj->dev, !shmem->pages) ||
            shmem->madv < 0) {
                ret = VM_FAULT_SIGBUS;
                goto out;
        }

        pfn = page_to_pfn(pages[page_offset]);
        ret = try_insert_pfn(vmf, order, pfn);

 out:
        dma_resv_unlock(shmem->base.resv);

        return ret;
}

static vm_fault_t drm_gem_shmem_fault(struct vm_fault *vmf)
{
        return drm_gem_shmem_any_fault(vmf, 0);
}

static void drm_gem_shmem_vm_open(struct vm_area_struct *vma)
{
        struct drm_gem_object *obj = vma->vm_private_data;
        struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);

        drm_WARN_ON(obj->dev, drm_gem_is_imported(obj));

        dma_resv_lock(shmem->base.resv, NULL);

        /*
         * We should have already pinned the pages when the buffer was first
         * mmap'd, vm_open() just grabs an additional reference for the new
         * mm the vma is getting copied into (ie. on fork()).
         */
        drm_WARN_ON_ONCE(obj->dev,
                         !refcount_inc_not_zero(&shmem->pages_use_count));

        dma_resv_unlock(shmem->base.resv);

        drm_gem_vm_open(vma);
}

static void drm_gem_shmem_vm_close(struct vm_area_struct *vma)
{
        struct drm_gem_object *obj = vma->vm_private_data;
        struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);

        dma_resv_lock(shmem->base.resv, NULL);
        drm_gem_shmem_put_pages_locked(shmem);
        dma_resv_unlock(shmem->base.resv);

        drm_gem_vm_close(vma);
}

const struct vm_operations_struct drm_gem_shmem_vm_ops = {
        .fault = drm_gem_shmem_fault,
#ifdef CONFIG_ARCH_SUPPORTS_PMD_PFNMAP
        .huge_fault = drm_gem_shmem_any_fault,
#endif
        .open = drm_gem_shmem_vm_open,
        .close = drm_gem_shmem_vm_close,
};
EXPORT_SYMBOL_GPL(drm_gem_shmem_vm_ops);

/**
 * drm_gem_shmem_mmap - Memory-map a shmem GEM object
 * @shmem: shmem GEM object
 * @vma: VMA for the area to be mapped
 *
 * This function implements an augmented version of the GEM DRM file mmap
 * operation for shmem objects.
 *
 * Returns:
 * 0 on success or a negative error code on failure.
 */
int drm_gem_shmem_mmap(struct drm_gem_shmem_object *shmem, struct vm_area_struct *vma)
{
        struct drm_gem_object *obj = &shmem->base;
        int ret;

        if (drm_gem_is_imported(obj)) {
                /* Reset both vm_ops and vm_private_data, so we don't end up with
                 * vm_ops pointing to our implementation if the dma-buf backend
                 * doesn't set those fields.
                 */
                vma->vm_private_data = NULL;
                vma->vm_ops = NULL;

                ret = dma_buf_mmap(obj->dma_buf, vma, 0);

                /* Drop the reference drm_gem_mmap_obj() acquired.*/
                if (!ret)
                        drm_gem_object_put(obj);

                return ret;
        }

        if (is_cow_mapping(vma->vm_flags))
                return -EINVAL;

        dma_resv_lock(shmem->base.resv, NULL);
        ret = drm_gem_shmem_get_pages_locked(shmem);
        dma_resv_unlock(shmem->base.resv);

        if (ret)
                return ret;

        vm_flags_set(vma, VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP);
        vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
        if (shmem->map_wc)
                vma->vm_page_prot = pgprot_writecombine(vma->vm_page_prot);

        return 0;
}
EXPORT_SYMBOL_GPL(drm_gem_shmem_mmap);

/**
 * drm_gem_shmem_print_info() - Print &drm_gem_shmem_object info for debugfs
 * @shmem: shmem GEM object
 * @p: DRM printer
 * @indent: Tab indentation level
 */
void drm_gem_shmem_print_info(const struct drm_gem_shmem_object *shmem,
                              struct drm_printer *p, unsigned int indent)
{
        if (drm_gem_is_imported(&shmem->base))
                return;

        drm_printf_indent(p, indent, "pages_pin_count=%u\n", refcount_read(&shmem->pages_pin_count));
        drm_printf_indent(p, indent, "pages_use_count=%u\n", refcount_read(&shmem->pages_use_count));
        drm_printf_indent(p, indent, "vmap_use_count=%u\n", refcount_read(&shmem->vmap_use_count));
        drm_printf_indent(p, indent, "vaddr=%p\n", shmem->vaddr);
}
EXPORT_SYMBOL_GPL(drm_gem_shmem_print_info);

/**
 * drm_gem_shmem_get_sg_table - Provide a scatter/gather table of pinned
 *                              pages for a shmem GEM object
 * @shmem: shmem GEM object
 *
 * This function exports a scatter/gather table suitable for PRIME usage by
 * calling the standard DMA mapping API.
 *
 * Drivers who need to acquire an scatter/gather table for objects need to call
 * drm_gem_shmem_get_pages_sgt() instead.
 *
 * Returns:
 * A pointer to the scatter/gather table of pinned pages or error pointer on failure.
 */
struct sg_table *drm_gem_shmem_get_sg_table(struct drm_gem_shmem_object *shmem)
{
        struct drm_gem_object *obj = &shmem->base;

        drm_WARN_ON(obj->dev, drm_gem_is_imported(obj));

        return drm_prime_pages_to_sg(obj->dev, shmem->pages, obj->size >> PAGE_SHIFT);
}
EXPORT_SYMBOL_GPL(drm_gem_shmem_get_sg_table);

static struct sg_table *drm_gem_shmem_get_pages_sgt_locked(struct drm_gem_shmem_object *shmem)
{
        struct drm_gem_object *obj = &shmem->base;
        int ret;
        struct sg_table *sgt;

        if (shmem->sgt)
                return shmem->sgt;

        drm_WARN_ON(obj->dev, drm_gem_is_imported(obj));

        ret = drm_gem_shmem_get_pages_locked(shmem);
        if (ret)
                return ERR_PTR(ret);

        sgt = drm_gem_shmem_get_sg_table(shmem);
        if (IS_ERR(sgt)) {
                ret = PTR_ERR(sgt);
                goto err_put_pages;
        }
        /* Map the pages for use by the h/w. */
        ret = dma_map_sgtable(obj->dev->dev, sgt, DMA_BIDIRECTIONAL, 0);
        if (ret)
                goto err_free_sgt;

        shmem->sgt = sgt;

        return sgt;

err_free_sgt:
        sg_free_table(sgt);
        kfree(sgt);
err_put_pages:
        drm_gem_shmem_put_pages_locked(shmem);
        return ERR_PTR(ret);
}

/**
 * drm_gem_shmem_get_pages_sgt - Pin pages, dma map them, and return a
 *                               scatter/gather table for a shmem GEM object.
 * @shmem: shmem GEM object
 *
 * This function returns a scatter/gather table suitable for driver usage. If
 * the sg table doesn't exist, the pages are pinned, dma-mapped, and a sg
 * table created.
 *
 * This is the main function for drivers to get at backing storage, and it hides
 * and difference between dma-buf imported and natively allocated objects.
 * drm_gem_shmem_get_sg_table() should not be directly called by drivers.
 *
 * Returns:
 * A pointer to the scatter/gather table of pinned pages or errno on failure.
 */
struct sg_table *drm_gem_shmem_get_pages_sgt(struct drm_gem_shmem_object *shmem)
{
        int ret;
        struct sg_table *sgt;

        ret = dma_resv_lock_interruptible(shmem->base.resv, NULL);
        if (ret)
                return ERR_PTR(ret);
        sgt = drm_gem_shmem_get_pages_sgt_locked(shmem);
        dma_resv_unlock(shmem->base.resv);

        return sgt;
}
EXPORT_SYMBOL_GPL(drm_gem_shmem_get_pages_sgt);

/**
 * drm_gem_shmem_prime_import_sg_table - Produce a shmem GEM object from
 *                 another driver's scatter/gather table of pinned pages
 * @dev: Device to import into
 * @attach: DMA-BUF attachment
 * @sgt: Scatter/gather table of pinned pages
 *
 * This function imports a scatter/gather table exported via DMA-BUF by
 * another driver. Drivers that use the shmem helpers should set this as their
 * &drm_driver.gem_prime_import_sg_table callback.
 *
 * Returns:
 * A pointer to a newly created GEM object or an ERR_PTR-encoded negative
 * error code on failure.
 */
struct drm_gem_object *
drm_gem_shmem_prime_import_sg_table(struct drm_device *dev,
                                    struct dma_buf_attachment *attach,
                                    struct sg_table *sgt)
{
        size_t size = PAGE_ALIGN(attach->dmabuf->size);
        struct drm_gem_shmem_object *shmem;

        shmem = __drm_gem_shmem_create(dev, size, true);
        if (IS_ERR(shmem))
                return ERR_CAST(shmem);

        shmem->sgt = sgt;

        drm_dbg_prime(dev, "size = %zu\n", size);

        return &shmem->base;
}
EXPORT_SYMBOL_GPL(drm_gem_shmem_prime_import_sg_table);

/**
 * drm_gem_shmem_prime_import_no_map - Import dmabuf without mapping its sg_table
 * @dev: Device to import into
 * @dma_buf: dma-buf object to import
 *
 * Drivers that use the shmem helpers but also wants to import dmabuf without
 * mapping its sg_table can use this as their &drm_driver.gem_prime_import
 * implementation.
 */
struct drm_gem_object *drm_gem_shmem_prime_import_no_map(struct drm_device *dev,
                                                         struct dma_buf *dma_buf)
{
        struct dma_buf_attachment *attach;
        struct drm_gem_shmem_object *shmem;
        struct drm_gem_object *obj;
        size_t size;
        int ret;

        if (drm_gem_is_prime_exported_dma_buf(dev, dma_buf)) {
                /*
                 * Importing dmabuf exported from our own gem increases
                 * refcount on gem itself instead of f_count of dmabuf.
                 */
                obj = dma_buf->priv;
                drm_gem_object_get(obj);
                return obj;
        }

        attach = dma_buf_attach(dma_buf, dev->dev);
        if (IS_ERR(attach))
                return ERR_CAST(attach);

        get_dma_buf(dma_buf);

        size = PAGE_ALIGN(attach->dmabuf->size);

        shmem = __drm_gem_shmem_create(dev, size, true);
        if (IS_ERR(shmem)) {
                ret = PTR_ERR(shmem);
                goto fail_detach;
        }

        drm_dbg_prime(dev, "size = %zu\n", size);

        shmem->base.import_attach = attach;
        shmem->base.resv = dma_buf->resv;

        return &shmem->base;

fail_detach:
        dma_buf_detach(dma_buf, attach);
        dma_buf_put(dma_buf);

        return ERR_PTR(ret);
}
EXPORT_SYMBOL_GPL(drm_gem_shmem_prime_import_no_map);

/*
 * Kunit helpers
 */

#if IS_ENABLED(CONFIG_KUNIT)
int drm_gem_shmem_vmap(struct drm_gem_shmem_object *shmem, struct iosys_map *map)
{
        struct drm_gem_object *obj = &shmem->base;
        int ret;

        ret = dma_resv_lock_interruptible(obj->resv, NULL);
        if (ret)
                return ret;
        ret = drm_gem_shmem_vmap_locked(shmem, map);
        dma_resv_unlock(obj->resv);

        return ret;
}
EXPORT_SYMBOL_IF_KUNIT(drm_gem_shmem_vmap);

void drm_gem_shmem_vunmap(struct drm_gem_shmem_object *shmem, struct iosys_map *map)
{
        struct drm_gem_object *obj = &shmem->base;

        dma_resv_lock_interruptible(obj->resv, NULL);
        drm_gem_shmem_vunmap_locked(shmem, map);
        dma_resv_unlock(obj->resv);
}
EXPORT_SYMBOL_IF_KUNIT(drm_gem_shmem_vunmap);

int drm_gem_shmem_madvise(struct drm_gem_shmem_object *shmem, int madv)
{
        struct drm_gem_object *obj = &shmem->base;
        int ret;

        ret = dma_resv_lock_interruptible(obj->resv, NULL);
        if (ret)
                return ret;
        ret = drm_gem_shmem_madvise_locked(shmem, madv);
        dma_resv_unlock(obj->resv);

        return ret;
}
EXPORT_SYMBOL_IF_KUNIT(drm_gem_shmem_madvise);

int drm_gem_shmem_purge(struct drm_gem_shmem_object *shmem)
{
        struct drm_gem_object *obj = &shmem->base;
        int ret;

        ret = dma_resv_lock_interruptible(obj->resv, NULL);
        if (ret)
                return ret;
        drm_gem_shmem_purge_locked(shmem);
        dma_resv_unlock(obj->resv);

        return 0;
}
EXPORT_SYMBOL_IF_KUNIT(drm_gem_shmem_purge);
#endif

MODULE_DESCRIPTION("DRM SHMEM memory-management helpers");
MODULE_IMPORT_NS("DMA_BUF");
MODULE_LICENSE("GPL");