Re: [PATCH v5 4/5] drm: Add library for shmem backed GEM objects

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On Wed, Oct 17, 2018 at 03:04:53PM +0200, Noralf Trønnes wrote:
> This adds a library for shmem backed GEM objects.
> 
> v5:
> - Drop drm_gem_shmem_prime_mmap() (Daniel Vetter)
> - drm_gem_shmem_mmap(): Subtract drm_vma_node_start() to get the real
>   vma->vm_pgoff
> - drm_gem_shmem_fault(): Use vmf->pgoff now that vma->vm_pgoff is correct
> 
> v4:
> - Drop cache modes (Thomas Hellstrom)
> - Add a GEM attached vtable
> 
> v3:
> - Grammar (Sam Ravnborg)
> - s/drm_gem_shmem_put_pages_unlocked/drm_gem_shmem_put_pages_locked/
>   (Sam Ravnborg)
> - Add debug output in error path (Sam Ravnborg)
> 
> Signed-off-by: Noralf Trønnes <noralf@xxxxxxxxxxx>
> ---
>  Documentation/gpu/drm-kms-helpers.rst  |  12 +
>  drivers/gpu/drm/Kconfig                |   6 +
>  drivers/gpu/drm/Makefile               |   1 +
>  drivers/gpu/drm/drm_gem_shmem_helper.c | 551 +++++++++++++++++++++++++++++++++
>  include/drm/drm_gem_shmem_helper.h     | 153 +++++++++
>  5 files changed, 723 insertions(+)
>  create mode 100644 drivers/gpu/drm/drm_gem_shmem_helper.c
>  create mode 100644 include/drm/drm_gem_shmem_helper.h
> 
> diff --git a/Documentation/gpu/drm-kms-helpers.rst b/Documentation/gpu/drm-kms-helpers.rst
> index 4b4dc236ef6f..8305d3566928 100644
> --- a/Documentation/gpu/drm-kms-helpers.rst
> +++ b/Documentation/gpu/drm-kms-helpers.rst
> @@ -335,3 +335,15 @@ Legacy CRTC/Modeset Helper Functions Reference
>  
>  .. kernel-doc:: drivers/gpu/drm/drm_crtc_helper.c
>     :export:
> +
> +SHMEM GEM Helper Reference
> +==========================
> +
> +.. kernel-doc:: drivers/gpu/drm/drm_gem_shmem_helper.c
> +   :doc: overview
> +
> +.. kernel-doc:: include/drm/drm_gem_shmem_helper.h
> +   :internal:
> +
> +.. kernel-doc:: drivers/gpu/drm/drm_gem_shmem_helper.c
> +   :export:

This doesn't make sense here imo - put them right next to the cma helpers
in drm-mm.rst instead?

> diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
> index 736b7e67e4ec..46090a36f52e 100644
> --- a/drivers/gpu/drm/Kconfig
> +++ b/drivers/gpu/drm/Kconfig
> @@ -157,6 +157,12 @@ config DRM_KMS_CMA_HELPER
>  	help
>  	  Choose this if you need the KMS CMA helper functions
>  
> +config DRM_GEM_SHMEM_HELPER
> +	bool
> +	depends on DRM
> +	help
> +	  Choose this if you need the GEM shmem helper functions
> +
>  config DRM_VM
>  	bool
>  	depends on DRM && MMU
> diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile
> index 576ba985e138..8733ceb41292 100644
> --- a/drivers/gpu/drm/Makefile
> +++ b/drivers/gpu/drm/Makefile
> @@ -25,6 +25,7 @@ drm-$(CONFIG_DRM_LIB_RANDOM) += lib/drm_random.o
>  drm-$(CONFIG_DRM_VM) += drm_vm.o
>  drm-$(CONFIG_COMPAT) += drm_ioc32.o
>  drm-$(CONFIG_DRM_GEM_CMA_HELPER) += drm_gem_cma_helper.o
> +drm-$(CONFIG_DRM_GEM_SHMEM_HELPER) += drm_gem_shmem_helper.o
>  drm-$(CONFIG_PCI) += ati_pcigart.o
>  drm-$(CONFIG_DRM_PANEL) += drm_panel.o
>  drm-$(CONFIG_OF) += drm_of.o
> diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c
> new file mode 100644
> index 000000000000..c4eec51d3282
> --- /dev/null
> +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
> @@ -0,0 +1,551 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright 2018 Noralf Trønnes
> + */
> +
> +#include <linux/dma-buf.h>
> +#include <linux/export.h>
> +#include <linux/mutex.h>
> +#include <linux/shmem_fs.h>
> +#include <linux/slab.h>
> +#include <linux/vmalloc.h>
> +
> +#include <drm/drm_device.h>
> +#include <drm/drm_drv.h>
> +#include <drm/drm_gem_shmem_helper.h>
> +#include <drm/drm_prime.h>
> +#include <drm/drm_print.h>
> +
> +/**
> + * DOC: overview
> + *
> + * This library provides helpers for GEM objects backed by shmem buffers
> + * allocated using anonymous pageable memory.

Would be neat to insert a link to the cma version here (and to the gem
version in the cma helpers) and spend a few words on when to use each.

> + */
> +
> +static const struct drm_gem_object_funcs drm_gem_shmem_funcs = {
> +	.free = drm_gem_shmem_free_object,
> +	.print_info = drm_gem_shmem_print_info,
> +	.pin = drm_gem_shmem_pin,
> +	.unpin = drm_gem_shmem_unpin,
> +	.get_sg_table = drm_gem_shmem_get_sg_table,
> +	.vmap = drm_gem_shmem_vmap,
> +	.vunmap = drm_gem_shmem_vunmap,
> +	.vm_ops = &drm_gem_shmem_vm_ops,
> +};
> +
> +/**
> + * 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)
> +{
> +	struct drm_gem_shmem_object *shmem;
> +	struct drm_gem_object *obj;
> +	int ret;
> +
> +	size = PAGE_ALIGN(size);
> +
> +	if (dev->driver->gem_create_object)
> +		obj = dev->driver->gem_create_object(dev, size);
> +	else
> +		obj = kzalloc(sizeof(*shmem), GFP_KERNEL);
> +	if (!obj)
> +		return ERR_PTR(-ENOMEM);
> +
> +	if (!obj->funcs)
> +		obj->funcs = &drm_gem_shmem_funcs;
> +
> +	ret = drm_gem_object_init(dev, obj, size);
> +	if (ret)
> +		goto err_free;
> +
> +	ret = drm_gem_create_mmap_offset(obj);
> +	if (ret)
> +		goto err_release;
> +
> +	shmem = to_drm_gem_shmem_obj(obj);
> +	mutex_init(&shmem->pages_lock);
> +	mutex_init(&shmem->vmap_lock);
> +
> +	return shmem;
> +
> +err_release:
> +	drm_gem_object_release(obj);
> +err_free:
> +	kfree(shmem);
> +
> +	return ERR_PTR(ret);
> +}
> +EXPORT_SYMBOL_GPL(drm_gem_shmem_create);
> +
> +/**
> + * drm_gem_shmem_free_object - Free resources associated with a shmem GEM object
> + * @obj: 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_object(struct drm_gem_object *obj)
> +{
> +	struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
> +
> +	WARN_ON(shmem->vmap_use_count);
> +
> +	if (obj->import_attach) {
> +		shmem->pages_use_count--;
> +		drm_prime_gem_destroy(obj, shmem->sgt);
> +		kvfree(shmem->pages);
> +	}
> +
> +	WARN_ON(shmem->pages_use_count);
> +
> +	drm_gem_object_release(obj);
> +	mutex_destroy(&shmem->pages_lock);
> +	mutex_destroy(&shmem->vmap_lock);
> +	kfree(shmem);
> +}
> +EXPORT_SYMBOL_GPL(drm_gem_shmem_free_object);
> +
> +static int drm_gem_shmem_get_pages_locked(struct drm_gem_shmem_object *shmem)
> +{
> +	struct drm_gem_object *obj = &shmem->base;
> +	struct page **pages;
> +
> +	if (shmem->pages_use_count++ > 0)
> +		return 0;
> +
> +	pages = drm_gem_get_pages(obj);

I think moving the drm_gem_get/put_pages into the shmem helper here would
be a good cleanup. Plus aligning the prefix to drm_gem_shmem - they really
only work with shmem, not cma gem bo.

> +	if (IS_ERR(pages)) {
> +		DRM_DEBUG_KMS("Failed to get pages (%ld)\n", PTR_ERR(pages));
> +		shmem->pages_use_count = 0;
> +		return PTR_ERR(pages);
> +	}
> +
> +	shmem->pages = pages;
> +
> +	return 0;
> +}
> +
> +/*
> + * drm_gem_shmem_get_pages - Allocate backing pages for a shmem GEM object
> + * @shmem: shmem GEM object
> + *
> + * This function makes sure that backing pages exists for the shmem GEM object
> + * and increases the use count.
> + *
> + * Returns:
> + * 0 on success or a negative error code on failure.
> + */
> +int drm_gem_shmem_get_pages(struct drm_gem_shmem_object *shmem)
> +{
> +	int ret;
> +
> +	ret = mutex_lock_interruptible(&shmem->pages_lock);
> +	if (ret)
> +		return ret;
> +	ret = drm_gem_shmem_get_pages_locked(shmem);
> +	mutex_unlock(&shmem->pages_lock);
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL(drm_gem_shmem_get_pages);
> +
> +static void drm_gem_shmem_put_pages_locked(struct drm_gem_shmem_object *shmem)
> +{
> +	struct drm_gem_object *obj = &shmem->base;
> +
> +	if (WARN_ON_ONCE(!shmem->pages_use_count))
> +		return;
> +
> +	if (--shmem->pages_use_count > 0)
> +		return;
> +
> +	drm_gem_put_pages(obj, shmem->pages,
> +			  shmem->pages_mark_dirty_on_put,
> +			  shmem->pages_mark_accessed_on_put);
> +	shmem->pages = NULL;
> +}
> +
> +/*
> + * drm_gem_shmem_put_pages - 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(struct drm_gem_shmem_object *shmem)
> +{
> +	mutex_lock(&shmem->pages_lock);
> +	drm_gem_shmem_put_pages_locked(shmem);
> +	mutex_unlock(&shmem->pages_lock);
> +}
> +EXPORT_SYMBOL(drm_gem_shmem_put_pages);
> +
> +/**
> + * drm_gem_shmem_pin - Pin backing pages for a shmem GEM object
> + * @obj: 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_object *obj)
> +{
> +	struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
> +
> +	return drm_gem_shmem_get_pages(shmem);
> +}
> +EXPORT_SYMBOL(drm_gem_shmem_pin);
> +
> +/**
> + * drm_gem_shmem_unpin - Unpin backing pages for a shmem GEM object
> + * @obj: GEM object
> + *
> + * This function removes the requirement that the backing pages are pinned in
> + * memory.
> + */
> +void drm_gem_shmem_unpin(struct drm_gem_object *obj)
> +{
> +	struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
> +
> +	drm_gem_shmem_put_pages(shmem);
> +}
> +EXPORT_SYMBOL(drm_gem_shmem_unpin);
> +
> +static void *drm_gem_shmem_vmap_locked(struct drm_gem_shmem_object *shmem)
> +{
> +	struct drm_gem_object *obj = &shmem->base;
> +	int ret;
> +
> +	if (shmem->vmap_use_count++ > 0)
> +		return shmem->vaddr;
> +
> +	ret = drm_gem_shmem_get_pages(shmem);
> +	if (ret)
> +		goto err_zero_use;
> +
> +	if (obj->import_attach)
> +		shmem->vaddr = dma_buf_vmap(obj->import_attach->dmabuf);
> +	else
> +		shmem->vaddr = vmap(shmem->pages, obj->size >> PAGE_SHIFT, VM_MAP, PAGE_KERNEL);
> +
> +	if (!shmem->vaddr) {
> +		DRM_DEBUG_KMS("Failed to vmap pages\n");
> +		ret = -ENOMEM;
> +		goto err_put_pages;
> +	}
> +
> +	return shmem->vaddr;
> +
> +err_put_pages:
> +	drm_gem_shmem_put_pages(shmem);
> +err_zero_use:
> +	shmem->vmap_use_count = 0;
> +
> +	return ERR_PTR(ret);
> +}
> +
> +/*
> + * drm_gem_shmem_vmap - Create a virtual mapping for a shmem GEM object
> + * @shmem: shmem GEM object
> + *
> + * This function makes sure that a virtual address exists for the buffer backing
> + * the shmem GEM object.
> + *
> + * Returns:
> + * 0 on success or a negative error code on failure.
> + */
> +void *drm_gem_shmem_vmap(struct drm_gem_object *obj)
> +{
> +	struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
> +	void *vaddr;
> +	int ret;
> +
> +	ret = mutex_lock_interruptible(&shmem->vmap_lock);
> +	if (ret)
> +		return ERR_PTR(ret);
> +	vaddr = drm_gem_shmem_vmap_locked(shmem);
> +	mutex_unlock(&shmem->vmap_lock);
> +
> +	return vaddr;
> +}
> +EXPORT_SYMBOL(drm_gem_shmem_vmap);
> +
> +static void drm_gem_shmem_vunmap_locked(struct drm_gem_shmem_object *shmem)
> +{
> +	struct drm_gem_object *obj = &shmem->base;
> +
> +	if (WARN_ON_ONCE(!shmem->vmap_use_count))
> +		return;
> +
> +	if (--shmem->vmap_use_count > 0)
> +		return;
> +
> +	if (obj->import_attach)
> +		dma_buf_vunmap(obj->import_attach->dmabuf, shmem->vaddr);
> +	else
> +		vunmap(shmem->vaddr);
> +
> +	shmem->vaddr = NULL;
> +	drm_gem_shmem_put_pages(shmem);
> +}
> +
> +/*
> + * drm_gem_shmem_vunmap - Unmap a virtual mapping fo a shmem GEM object
> + * @shmem: shmem GEM object
> + *
> + * This function removes the virtual address when use count drops to zero.
> + */
> +void drm_gem_shmem_vunmap(struct drm_gem_object *obj, void *vaddr)
> +{
> +	struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
> +
> +	mutex_lock(&shmem->vmap_lock);
> +	drm_gem_shmem_vunmap_locked(shmem);
> +	mutex_unlock(&shmem->vmap_lock);
> +}
> +EXPORT_SYMBOL(drm_gem_shmem_vunmap);
> +
> +static struct drm_gem_shmem_object *
> +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 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_unlocked(&shmem->base);
> +	if (ret)
> +		return ERR_PTR(ret);
> +
> +	return shmem;
> +}
> +
> +/**
> + * 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)
> +{
> +	u32 min_pitch = DIV_ROUND_UP(args->width * args->bpp, 8);
> +	struct drm_gem_shmem_object *shmem;
> +
> +	if (!args->pitch || !args->size) {
> +		args->pitch = min_pitch;
> +		args->size = args->pitch * args->height;
> +	} else {
> +		/* ensure sane minimum values */
> +		if (args->pitch < min_pitch)
> +			args->pitch = min_pitch;
> +		if (args->size < args->pitch * args->height)
> +			args->size = args->pitch * args->height;
> +	}
> +
> +	shmem = drm_gem_shmem_create_with_handle(file, dev, args->size, &args->handle);
> +
> +	return PTR_ERR_OR_ZERO(shmem);
> +}
> +EXPORT_SYMBOL_GPL(drm_gem_shmem_dumb_create);
> +
> +static vm_fault_t drm_gem_shmem_fault(struct vm_fault *vmf)
> +{
> +	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;
> +	struct page *page;
> +
> +	if (vmf->pgoff > num_pages || WARN_ON_ONCE(!shmem->pages))
> +		return VM_FAULT_SIGBUS;
> +
> +	page = shmem->pages[vmf->pgoff];
> +
> +	return vmf_insert_page(vma, vmf->address, page);
> +}
> +
> +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);
> +
> +	drm_gem_shmem_put_pages(shmem);

Imbalance get/put_pages here, if someone forks (which is what calls
vm_ops->open on an existing vma).

> +	drm_gem_vm_close(vma);
> +}
> +
> +const struct vm_operations_struct drm_gem_shmem_vm_ops = {
> +	.fault = drm_gem_shmem_fault,
> +	.open = drm_gem_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
> + * @filp: File 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. Drivers which employ the shmem helpers should
> + * use this function as their &file_operations.mmap handler in the DRM device file's
> + * file_operations structure.
> + *
> + * Instead of directly referencing this function, drivers should use the
> + * DEFINE_DRM_GEM_SHMEM_FOPS() macro.
> + *
> + * Returns:
> + * 0 on success or a negative error code on failure.
> + */

Between cma helpers, gem shmem helpers and the drm_gem_mmap we now have
quite a bit a confusion of mmap functions. I think it'd be good to update
the kerneldoc for drm_gem_mmap() to point at these here (both the shmem
and cma version), so that people prefer to use these helpers here. Direct
call to drm_gem_mmap would only be needed if you want to use your own
vm_ops.

> +int drm_gem_shmem_mmap(struct file *filp, struct vm_area_struct *vma)
> +{
> +	struct drm_gem_shmem_object *shmem;
> +	int ret;
> +
> +	ret = drm_gem_mmap(filp, vma);
> +	if (ret)
> +		return ret;
> +
> +	shmem = to_drm_gem_shmem_obj(vma->vm_private_data);
> +
> +	ret = drm_gem_shmem_get_pages(shmem);
> +	if (ret) {
> +		drm_gem_vm_close(vma);
> +		return ret;
> +	}
> +
> +	/* VM_PFNMAP was set by drm_gem_mmap() */
> +	vma->vm_flags &= ~VM_PFNMAP;
> +	vma->vm_flags |= VM_MIXEDMAP;
> +	vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
> +
> +	fput(vma->vm_file);
> +	vma->vm_file = get_file(shmem->base.filp);
> +	/* Remove the fake offset */
> +	vma->vm_pgoff -= drm_vma_node_start(&shmem->base.vma_node);
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(drm_gem_shmem_mmap);

Looking through your mmap code there's 2 bits:
- shmem isn't coherent, if you try to actually buffer share this with
  prime I expect it'll fail badly. We'd need begin/end_cpu_access
  callbacks in dma_buf_ops to make this work. So not entirely sure how
  much value there is in implementing the prime mmap stuff (but doesn't
  hurt to have it).

- shmem already has an mmap implemtation, you can just use that. Needs a
  similar mmap forwarding trick as you've done for prime mmap, but instead
  you forward to obj->base.filp. That allows you to cut away all the
  vm_ops and everything. I guess we could clean this up in a follow-up,
  since it doesn't have an effect on the interfaces exposed to drivers. At
  least not a big one, drm_gem_shmem_vm_ops would disappear.

> +
> +/**
> + * drm_gem_shmem_print_info() - Print &drm_gem_shmem_object info for debugfs
> + * @p: DRM printer
> + * @indent: Tab indentation level
> + * @obj: GEM object

Would be good to reference the hook this is meant for:
&drm_gem_object_funcs.print_info, same for all the others. For those
drivers that want to pick&choose.

Cheers, Daniel

> + */
> +void drm_gem_shmem_print_info(struct drm_printer *p, unsigned int indent,
> +			      const struct drm_gem_object *obj)
> +{
> +	const struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
> +
> +	drm_printf_indent(p, indent, "pages_use_count=%u\n", shmem->pages_use_count);
> +	drm_printf_indent(p, indent, "vmap_use_count=%u\n", shmem->vmap_use_count);
> +	drm_printf_indent(p, indent, "vaddr=%p\n", shmem->vaddr);
> +}
> +EXPORT_SYMBOL(drm_gem_shmem_print_info);
> +
> +/**
> + * drm_gem_shmem_get_sg_table - Provide a scatter/gather table of pinned
> + *                              pages for a shmem GEM object
> + * @obj: GEM object
> + *
> + * This function exports a scatter/gather table suitable for PRIME usage by
> + * calling the standard DMA mapping API.
> + *
> + * Returns:
> + * A pointer to the scatter/gather table of pinned pages or NULL on failure.
> + */
> +struct sg_table *drm_gem_shmem_get_sg_table(struct drm_gem_object *obj)
> +{
> +	struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
> +
> +	return drm_prime_pages_to_sg(shmem->pages, obj->size >> PAGE_SHIFT);
> +}
> +EXPORT_SYMBOL_GPL(drm_gem_shmem_get_sg_table);
> +
> +/**
> + * 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);
> +	size_t npages = size >> PAGE_SHIFT;
> +	struct drm_gem_shmem_object *shmem;
> +	int ret;
> +
> +	shmem = drm_gem_shmem_create(dev, size);
> +	if (IS_ERR(shmem))
> +		return ERR_CAST(shmem);
> +
> +	shmem->pages = kvmalloc_array(npages, sizeof(struct page *), GFP_KERNEL);
> +	if (!shmem->pages) {
> +		ret = -ENOMEM;
> +		goto err_free_gem;
> +	}
> +
> +	ret = drm_prime_sg_to_page_addr_arrays(sgt, shmem->pages, NULL, npages);
> +	if (ret < 0)
> +		goto err_free_array;
> +
> +	shmem->sgt = sgt;
> +	shmem->pages_use_count = 1; /* Permanently pinned from our point of view */
> +
> +	DRM_DEBUG_PRIME("size = %zu\n", size);
> +
> +	return &shmem->base;
> +
> +err_free_array:
> +	kvfree(shmem->pages);
> +err_free_gem:
> +	drm_gem_object_put_unlocked(&shmem->base);
> +
> +	return ERR_PTR(ret);
> +}
> +EXPORT_SYMBOL_GPL(drm_gem_shmem_prime_import_sg_table);
> diff --git a/include/drm/drm_gem_shmem_helper.h b/include/drm/drm_gem_shmem_helper.h
> new file mode 100644
> index 000000000000..26b05e06407d
> --- /dev/null
> +++ b/include/drm/drm_gem_shmem_helper.h
> @@ -0,0 +1,153 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +
> +#ifndef __DRM_GEM_SHMEM_HELPER_H__
> +#define __DRM_GEM_SHMEM_HELPER_H__
> +
> +#include <linux/fs.h>
> +#include <linux/mm.h>
> +#include <linux/mutex.h>
> +
> +#include <drm/drm_file.h>
> +#include <drm/drm_gem.h>
> +#include <drm/drm_ioctl.h>
> +#include <drm/drm_prime.h>
> +
> +struct dma_buf_attachment;
> +struct drm_mode_create_dumb;
> +struct drm_printer;
> +struct sg_table;
> +
> +/**
> + * struct drm_gem_shmem_object - GEM object backed by shmem
> + */
> +struct drm_gem_shmem_object {
> +	/**
> +	 * @base: Base GEM object
> +	 */
> +	struct drm_gem_object base;
> +
> +	/**
> +	 * @pages_lock: Protects the page table and use count
> +	 */
> +	struct mutex pages_lock;
> +
> +	/**
> +	 * @pages: Page table
> +	 */
> +	struct page **pages;
> +
> +	/**
> +	 * @pages_use_count:
> +	 *
> +	 * Reference count on the pages table.
> +	 * The pages are put when the count reaches zero.
> +	 */
> +	unsigned int pages_use_count;
> +
> +	/**
> +	 * @pages_mark_dirty_on_put:
> +	 *
> +	 * Mark pages as dirty when they are put.
> +	 */
> +	unsigned int pages_mark_dirty_on_put    : 1;
> +
> +	/**
> +	 * @pages_mark_accessed_on_put:
> +	 *
> +	 * Mark pages as accessed when they are put.
> +	 */
> +	unsigned int pages_mark_accessed_on_put : 1;
> +
> +	/**
> +	 * @sgt: Scatter/gather table for imported PRIME buffers
> +	 */
> +	struct sg_table *sgt;
> +
> +	/**
> +	 * @vmap_lock: Protects the vmap address and use count
> +	 */
> +	struct mutex vmap_lock;
> +
> +	/**
> +	 * @vaddr: Kernel virtual address of the backing memory
> +	 */
> +	void *vaddr;
> +
> +	/**
> +	 * @vmap_use_count:
> +	 *
> +	 * Reference count on the virtual address.
> +	 * The address are un-mapped when the count reaches zero.
> +	 */
> +	unsigned int vmap_use_count;
> +};
> +
> +#define to_drm_gem_shmem_obj(obj) \
> +	container_of(obj, struct drm_gem_shmem_object, base)
> +
> +/**
> + * DEFINE_DRM_GEM_SHMEM_FOPS() - Macro to generate file operations for shmem drivers
> + * @name: name for the generated structure
> + *
> + * This macro autogenerates a suitable &struct file_operations for shmem based
> + * drivers, which can be assigned to &drm_driver.fops. Note that this structure
> + * cannot be shared between drivers, because it contains a reference to the
> + * current module using THIS_MODULE.
> + *
> + * Note that the declaration is already marked as static - if you need a
> + * non-static version of this you're probably doing it wrong and will break the
> + * THIS_MODULE reference by accident.
> + */
> +#define DEFINE_DRM_GEM_SHMEM_FOPS(name) \
> +	static const struct file_operations name = {\
> +		.owner		= THIS_MODULE,\
> +		.open		= drm_open,\
> +		.release	= drm_release,\
> +		.unlocked_ioctl	= drm_ioctl,\
> +		.compat_ioctl	= drm_compat_ioctl,\
> +		.poll		= drm_poll,\
> +		.read		= drm_read,\
> +		.llseek		= noop_llseek,\
> +		.mmap		= drm_gem_shmem_mmap, \
> +	}
> +
> +struct drm_gem_shmem_object *drm_gem_shmem_create(struct drm_device *dev, size_t size);
> +void drm_gem_shmem_free_object(struct drm_gem_object *obj);
> +
> +int drm_gem_shmem_get_pages(struct drm_gem_shmem_object *shmem);
> +void drm_gem_shmem_put_pages(struct drm_gem_shmem_object *shmem);
> +int drm_gem_shmem_pin(struct drm_gem_object *obj);
> +void drm_gem_shmem_unpin(struct drm_gem_object *obj);
> +void *drm_gem_shmem_vmap(struct drm_gem_object *obj);
> +void drm_gem_shmem_vunmap(struct drm_gem_object *obj, void *vaddr);
> +
> +int drm_gem_shmem_dumb_create(struct drm_file *file, struct drm_device *dev,
> +			      struct drm_mode_create_dumb *args);
> +
> +int drm_gem_shmem_mmap(struct file *filp, struct vm_area_struct *vma);
> +
> +extern const struct vm_operations_struct drm_gem_shmem_vm_ops;
> +
> +void drm_gem_shmem_print_info(struct drm_printer *p, unsigned int indent,
> +			      const struct drm_gem_object *obj);
> +
> +struct sg_table *drm_gem_shmem_get_sg_table(struct drm_gem_object *obj);
> +struct drm_gem_object *
> +drm_gem_shmem_prime_import_sg_table(struct drm_device *dev,
> +				    struct dma_buf_attachment *attach,
> +				    struct sg_table *sgt);
> +
> +/**
> + * DRM_GEM_SHMEM_DRIVER_OPS - Default shmem GEM operations
> + *
> + * This macro provides a shortcut for setting the shmem GEM operations in
> + * the &drm_driver structure.
> + */
> +#define DRM_GEM_SHMEM_DRIVER_OPS \
> +	.prime_handle_to_fd	= drm_gem_prime_handle_to_fd, \
> +	.prime_fd_to_handle	= drm_gem_prime_fd_to_handle, \
> +	.gem_prime_import_sg_table = drm_gem_shmem_prime_import_sg_table, \
> +	.gem_prime_mmap		= drm_gem_prime_mmap, \
> +	.dumb_create		= drm_gem_shmem_dumb_create
> +
> +#endif /* __DRM_GEM_SHMEM_HELPER_H__ */
> -- 
> 2.15.1
> 
> _______________________________________________
> dri-devel mailing list
> dri-devel@xxxxxxxxxxxxxxxxxxxxx
> https://lists.freedesktop.org/mailman/listinfo/dri-devel

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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