Re: [RFC 2/3] drm/gem: Add drm_gem_object_funcs

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On Fri, Sep 21, 2018 at 06:42:29PM +0200, Noralf Trønnes wrote:
> This adds an optional function table on GEM objects.
> The main benefit is for drivers that support more than one type of
> memory (shmem,vram,cma) for their buffers depending on the hardware it
> runs on. With the callbacks attached to the GEM object itself, it is
> easier to have core helpers for the the various buffer types. The driver
> only has to make the decision about buffer type on GEM object creation
> and all other callbacks can be handled by the chosen helper.
> 
> drm_driver->gem_prime_res_obj has not been added since there's a todo to
> put a reservation_object into drm_gem_object.
> 
> The individual drm_driver callbacks take priority over the GEM attached
> callbacks.

I'd do this the other way round, make the new gem callbacks the clearly
favoured option.

> Signed-off-by: Noralf Trønnes <noralf@xxxxxxxxxxx>
> ---
>  drivers/gpu/drm/drm_client.c    |  12 ++--
>  drivers/gpu/drm/drm_fb_helper.c |   8 ++-
>  drivers/gpu/drm/drm_gem.c       | 108 +++++++++++++++++++++++++++++--
>  drivers/gpu/drm/drm_prime.c     |  40 ++++++------
>  include/drm/drm_gem.h           | 138 ++++++++++++++++++++++++++++++++++++++++
>  5 files changed, 272 insertions(+), 34 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_client.c b/drivers/gpu/drm/drm_client.c
> index 17d9a64e885e..eca7331762e4 100644
> --- a/drivers/gpu/drm/drm_client.c
> +++ b/drivers/gpu/drm/drm_client.c
> @@ -80,8 +80,7 @@ int drm_client_new(struct drm_device *dev, struct drm_client_dev *client,
>  {
>  	int ret;
>  
> -	if (!drm_core_check_feature(dev, DRIVER_MODESET) ||
> -	    !dev->driver->dumb_create || !dev->driver->gem_prime_vmap)
> +	if (!drm_core_check_feature(dev, DRIVER_MODESET) || !dev->driver->dumb_create)
>  		return -EOPNOTSUPP;

I guess the ->gem_prime_vmap check got lost, needs to be readded somewhere
I think.

>  
>  	if (funcs && !try_module_get(funcs->owner))
> @@ -212,8 +211,7 @@ static void drm_client_buffer_delete(struct drm_client_buffer *buffer)
>  {
>  	struct drm_device *dev = buffer->client->dev;
>  
> -	if (buffer->vaddr && dev->driver->gem_prime_vunmap)
> -		dev->driver->gem_prime_vunmap(buffer->gem, buffer->vaddr);
> +	drm_gem_vunmap(buffer->gem, buffer->vaddr);
>  
>  	if (buffer->gem)
>  		drm_gem_object_put_unlocked(buffer->gem);
> @@ -266,9 +264,9 @@ drm_client_buffer_create(struct drm_client_dev *client, u32 width, u32 height, u
>  	 * fd_install step out of the driver backend hooks, to make that
>  	 * final step optional for internal users.
>  	 */
> -	vaddr = dev->driver->gem_prime_vmap(obj);
> -	if (!vaddr) {
> -		ret = -ENOMEM;
> +	vaddr = drm_gem_vmap(obj);
> +	if (IS_ERR(vaddr)) {
> +		ret = PTR_ERR(vaddr);
>  		goto err_delete;
>  	}
>  
> diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
> index 8e95d0f7c71d..66969f0facbb 100644
> --- a/drivers/gpu/drm/drm_fb_helper.c
> +++ b/drivers/gpu/drm/drm_fb_helper.c
> @@ -38,6 +38,7 @@
>  #include <drm/drmP.h>
>  #include <drm/drm_crtc.h>
>  #include <drm/drm_fb_helper.h>
> +#include <drm/drm_gem.h>
>  #include <drm/drm_crtc_helper.h>
>  #include <drm/drm_atomic.h>
>  #include <drm/drm_atomic_helper.h>
> @@ -3010,9 +3011,12 @@ static void drm_fbdev_fb_destroy(struct fb_info *info)
>  static int drm_fbdev_fb_mmap(struct fb_info *info, struct vm_area_struct *vma)
>  {
>  	struct drm_fb_helper *fb_helper = info->par;
> +	struct drm_gem_object *obj = fb_helper->buffer->gem;
>  
> -	if (fb_helper->dev->driver->gem_prime_mmap)
> -		return fb_helper->dev->driver->gem_prime_mmap(fb_helper->buffer->gem, vma);
> +	if (obj->dev->driver->gem_prime_mmap)
> +		return obj->dev->driver->gem_prime_mmap(obj, vma);
> +	else if (obj->funcs && obj->funcs->mmap)
> +		return drm_gem_mmap_obj(obj, obj->size, vma);
>  	else
>  		return -ENODEV;
>  }
> diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c
> index 512078ebd97b..7da2549667ce 100644
> --- a/drivers/gpu/drm/drm_gem.c
> +++ b/drivers/gpu/drm/drm_gem.c
> @@ -259,6 +259,8 @@ drm_gem_object_release_handle(int id, void *ptr, void *data)
>  
>  	if (dev->driver->gem_close_object)
>  		dev->driver->gem_close_object(obj, file_priv);
> +	else if (obj->funcs && obj->funcs->close)
> +		obj->funcs->close(obj, file_priv);
>  
>  	if (drm_core_check_feature(dev, DRIVER_PRIME))
>  		drm_gem_remove_prime_handles(obj, file_priv);
> @@ -414,6 +416,10 @@ drm_gem_handle_create_tail(struct drm_file *file_priv,
>  		ret = dev->driver->gem_open_object(obj, file_priv);
>  		if (ret)
>  			goto err_revoke;
> +	} else if (obj->funcs && obj->funcs->open) {
> +		ret = obj->funcs->open(obj, file_priv);
> +		if (ret)
> +			goto err_revoke;
>  	}
>  
>  	*handlep = handle;
> @@ -841,6 +847,8 @@ drm_gem_object_free(struct kref *kref)
>  		WARN_ON(!mutex_is_locked(&dev->struct_mutex));
>  
>  		dev->driver->gem_free_object(obj);
> +	} else if (obj->funcs) {
> +		obj->funcs->free(obj);
>  	}
>  }
>  EXPORT_SYMBOL(drm_gem_object_free);
> @@ -864,13 +872,13 @@ drm_gem_object_put_unlocked(struct drm_gem_object *obj)
>  
>  	dev = obj->dev;
>  
> -	if (dev->driver->gem_free_object_unlocked) {
> -		kref_put(&obj->refcount, drm_gem_object_free);
> -	} else {
> +	if (dev->driver->gem_free_object) {
>  		might_lock(&dev->struct_mutex);
>  		if (kref_put_mutex(&obj->refcount, drm_gem_object_free,
>  				&dev->struct_mutex))
>  			mutex_unlock(&dev->struct_mutex);
> +	} else {
> +		kref_put(&obj->refcount, drm_gem_object_free);
>  	}
>  }
>  EXPORT_SYMBOL(drm_gem_object_put_unlocked);
> @@ -955,20 +963,30 @@ int drm_gem_mmap_obj(struct drm_gem_object *obj, unsigned long obj_size,
>  		     struct vm_area_struct *vma)
>  {
>  	struct drm_device *dev = obj->dev;
> +	int ret;
>  
>  	/* Check for valid size. */
>  	if (obj_size < vma->vm_end - vma->vm_start)
>  		return -EINVAL;
>  
> -	if (!dev->driver->gem_vm_ops)
> +	if (dev->driver->gem_vm_ops)
> +		vma->vm_ops = dev->driver->gem_vm_ops;
> +	else if (obj->funcs && obj->funcs->vm_ops)
> +		vma->vm_ops = obj->funcs->vm_ops;
> +	else
>  		return -EINVAL;

A bit a bikeshed, but if we go with these new ops, I'd put them first in
all the if ladders. Makes it a bit clearer while reading that they're the
recommended option.
>  
>  	vma->vm_flags |= VM_IO | VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP;
> -	vma->vm_ops = dev->driver->gem_vm_ops;
>  	vma->vm_private_data = obj;
>  	vma->vm_page_prot = pgprot_writecombine(vm_get_page_prot(vma->vm_flags));
>  	vma->vm_page_prot = pgprot_decrypted(vma->vm_page_prot);
>  
> +	if (obj->funcs && obj->funcs->mmap) {
> +		ret = obj->funcs->mmap(obj, vma);
> +		if (ret)
> +			return ret;
> +	}

I'm confused about this one here ... this is for prime mmap only iirc.

> +
>  	/* Take a ref for this mapping of the object, so that the fault
>  	 * handler can dereference the mmap offset's pointer to the object.
>  	 * This reference is cleaned up by the corresponding vm_close
> @@ -1068,4 +1086,84 @@ void drm_gem_print_info(struct drm_printer *p, unsigned int indent,
>  
>  	if (obj->dev->driver->gem_print_info)
>  		obj->dev->driver->gem_print_info(p, indent, obj);
> +	else if (obj->funcs && obj->funcs->print_info)
> +		obj->funcs->print_info(p, indent, obj);
>  }
> +
> +/**
> + * drm_gem_pin - Pin backing buffer in memory
> + * @obj: GEM object
> + *
> + * Make sure the backing buffer is pinned in memory.
> + *
> + * Returns:
> + * 0 on success or a negative error code on failure.
> + */
> +int drm_gem_pin(struct drm_gem_object *obj)
> +{
> +	if (obj->dev->driver->gem_prime_pin)
> +		return obj->dev->driver->gem_prime_pin(obj);
> +	else if (obj->funcs && obj->funcs->pin)
> +		return obj->funcs->pin(obj);
> +	else
> +		return 0;
> +}
> +EXPORT_SYMBOL(drm_gem_pin);
> +
> +/**
> + * drm_gem_pin - Unpin backing buffer from memory
> + * @obj: GEM object
> + *
> + * Relax the requirement that the backing buffer is pinned in memory.
> + */
> +void drm_gem_unpin(struct drm_gem_object *obj)
> +{
> +	if (obj->dev->driver->gem_prime_unpin)
> +		obj->dev->driver->gem_prime_unpin(obj);
> +	else if (obj->funcs && obj->funcs->unpin)
> +		obj->funcs->unpin(obj);
> +}
> +EXPORT_SYMBOL(drm_gem_unpin);
> +
> +/**
> + * drm_gem_vmap - Map buffer into kernel virtual address space
> + * @obj: GEM object
> + *
> + * Returns:
> + * A virtual pointer to a newly created GEM object or an ERR_PTR-encoded negative
> + * error code on failure.
> + */
> +void *drm_gem_vmap(struct drm_gem_object *obj)
> +{
> +	void *vaddr;
> +
> +	if (obj->dev->driver->gem_prime_vmap)
> +		vaddr = obj->dev->driver->gem_prime_vmap(obj);
> +	else if (obj->funcs && obj->funcs->vmap)
> +		vaddr = obj->funcs->vmap(obj);
> +	else
> +		vaddr = ERR_PTR(-EOPNOTSUPP);
> +
> +	if (!vaddr)
> +		vaddr = ERR_PTR(-ENOMEM);
> +
> +	return vaddr;
> +}
> +EXPORT_SYMBOL(drm_gem_vmap);
> +
> +/**
> + * drm_gem_vunmap - Remove buffer mapping from kernel virtual address space
> + * @obj: GEM object
> + * @vaddr: Virtual address (can be NULL)
> + */
> +void drm_gem_vunmap(struct drm_gem_object *obj, void *vaddr)
> +{
> +	if (!vaddr)
> +		return;
> +
> +	if (obj->dev->driver->gem_prime_vunmap)
> +		obj->dev->driver->gem_prime_vunmap(obj, vaddr);
> +	else if (obj->funcs && obj->funcs->vunmap)
> +		obj->funcs->vunmap(obj, vaddr);
> +}
> +EXPORT_SYMBOL(drm_gem_vunmap);
> diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c
> index 6721571749ff..7f5c9500136b 100644
> --- a/drivers/gpu/drm/drm_prime.c
> +++ b/drivers/gpu/drm/drm_prime.c
> @@ -199,7 +199,6 @@ int drm_gem_map_attach(struct dma_buf *dma_buf,
>  {
>  	struct drm_prime_attachment *prime_attach;
>  	struct drm_gem_object *obj = dma_buf->priv;
> -	struct drm_device *dev = obj->dev;
>  
>  	prime_attach = kzalloc(sizeof(*prime_attach), GFP_KERNEL);
>  	if (!prime_attach)
> @@ -208,10 +207,7 @@ int drm_gem_map_attach(struct dma_buf *dma_buf,
>  	prime_attach->dir = DMA_NONE;
>  	attach->priv = prime_attach;
>  
> -	if (!dev->driver->gem_prime_pin)
> -		return 0;
> -
> -	return dev->driver->gem_prime_pin(obj);
> +	return drm_gem_pin(obj);
>  }
>  EXPORT_SYMBOL(drm_gem_map_attach);
>  
> @@ -228,7 +224,6 @@ void drm_gem_map_detach(struct dma_buf *dma_buf,
>  {
>  	struct drm_prime_attachment *prime_attach = attach->priv;
>  	struct drm_gem_object *obj = dma_buf->priv;
> -	struct drm_device *dev = obj->dev;
>  
>  	if (prime_attach) {
>  		struct sg_table *sgt = prime_attach->sgt;
> @@ -247,8 +242,7 @@ void drm_gem_map_detach(struct dma_buf *dma_buf,
>  		attach->priv = NULL;
>  	}
>  
> -	if (dev->driver->gem_prime_unpin)
> -		dev->driver->gem_prime_unpin(obj);
> +	drm_gem_unpin(obj);
>  }
>  EXPORT_SYMBOL(drm_gem_map_detach);
>  
> @@ -310,7 +304,10 @@ struct sg_table *drm_gem_map_dma_buf(struct dma_buf_attachment *attach,
>  	if (WARN_ON(prime_attach->dir != DMA_NONE))
>  		return ERR_PTR(-EBUSY);
>  
> -	sgt = obj->dev->driver->gem_prime_get_sg_table(obj);

I think if we just check for obj->funcs here and then unconditionally
call, we avoid a bunch of pointer chasing for the new recommended path :-)

> +	if (obj->dev->driver->gem_prime_get_sg_table)
> +		sgt = obj->dev->driver->gem_prime_get_sg_table(obj);
> +	else
> +		sgt = obj->funcs->get_sg_table(obj);
>  
>  	if (!IS_ERR(sgt)) {
>  		if (!dma_map_sg_attrs(attach->dev, sgt->sgl, sgt->nents, dir,
> @@ -406,12 +403,13 @@ EXPORT_SYMBOL(drm_gem_dmabuf_release);
>  void *drm_gem_dmabuf_vmap(struct dma_buf *dma_buf)
>  {
>  	struct drm_gem_object *obj = dma_buf->priv;
> -	struct drm_device *dev = obj->dev;
> +	void *vaddr;
>  
> -	if (dev->driver->gem_prime_vmap)
> -		return dev->driver->gem_prime_vmap(obj);
> -	else
> -		return NULL;
> +	vaddr = drm_gem_vmap(obj);
> +	if (IS_ERR(vaddr))
> +		vaddr = NULL;
> +
> +	return vaddr;
>  }
>  EXPORT_SYMBOL(drm_gem_dmabuf_vmap);
>  
> @@ -426,10 +424,8 @@ EXPORT_SYMBOL(drm_gem_dmabuf_vmap);
>  void drm_gem_dmabuf_vunmap(struct dma_buf *dma_buf, void *vaddr)
>  {
>  	struct drm_gem_object *obj = dma_buf->priv;
> -	struct drm_device *dev = obj->dev;
>  
> -	if (dev->driver->gem_prime_vunmap)
> -		dev->driver->gem_prime_vunmap(obj, vaddr);
> +	drm_gem_vunmap(obj, vaddr);
>  }
>  EXPORT_SYMBOL(drm_gem_dmabuf_vunmap);
>  
> @@ -476,10 +472,12 @@ int drm_gem_dmabuf_mmap(struct dma_buf *dma_buf, struct vm_area_struct *vma)
>  	struct drm_gem_object *obj = dma_buf->priv;
>  	struct drm_device *dev = obj->dev;
>  
> -	if (!dev->driver->gem_prime_mmap)
> +	if (dev->driver->gem_prime_mmap)
> +		return dev->driver->gem_prime_mmap(obj, vma);
> +	else if (obj->funcs && obj->funcs->mmap)
> +		return drm_gem_mmap_obj(obj, obj->size, vma);
> +	else
>  		return -ENOSYS;
> -
> -	return dev->driver->gem_prime_mmap(obj, vma);
>  }
>  EXPORT_SYMBOL(drm_gem_dmabuf_mmap);
>  
> @@ -561,6 +559,8 @@ static struct dma_buf *export_and_register_object(struct drm_device *dev,
>  
>  	if (dev->driver->gem_prime_export)
>  		dmabuf = dev->driver->gem_prime_export(dev, obj, flags);
> +	else if (obj->funcs && obj->funcs->export)
> +		dmabuf = obj->funcs->export(obj, flags);
>  	else
>  		dmabuf = drm_gem_prime_export(dev, obj, flags);
>  	if (IS_ERR(dmabuf)) {
> diff --git a/include/drm/drm_gem.h b/include/drm/drm_gem.h
> index 3583b98a1718..3ae3665bf4e7 100644
> --- a/include/drm/drm_gem.h
> +++ b/include/drm/drm_gem.h
> @@ -38,6 +38,130 @@
>  
>  #include <drm/drm_vma_manager.h>
>  
> +struct drm_gem_object;
> +
> +/**
> + * struct drm_gem_object_funcs - GEM object functions
> + */
> +struct drm_gem_object_funcs {
> +	/**
> +	 * @free:
> +	 *
> +	 * Deconstructor for drm_gem_objects.
> +	 *
> +	 * This callback is mandatory.
> +	 */
> +	void (*free)(struct drm_gem_object *obj);
> +
> +	/**
> +	 * @open:
> +	 *
> +	 * Called upon GEM handle creation.
> +	 *
> +	 * This callback is optional.
> +	 */
> +	int (*open)(struct drm_gem_object *obj, struct drm_file *file);
> +
> +	/**
> +	 * @close_object:

@close:

> +	 *
> +	 * Called upon GEM handle release.
> +	 *
> +	 * This callback is optional.
> +	 */
> +	void (*close)(struct drm_gem_object *obj, struct drm_file *file);
> +
> +	/**
> +	 * @print_info:
> +	 *
> +	 * If driver subclasses struct &drm_gem_object, it can implement this
> +	 * optional hook for printing additional driver specific info.
> +	 *
> +	 * drm_printf_indent() should be used in the callback passing it the
> +	 * indent argument.
> +	 *
> +	 * This callback is called from drm_gem_print_info().
> +	 *
> +	 * This callback is optional.
> +	 */
> +	void (*print_info)(struct drm_printer *p, unsigned int indent,
> +			   const struct drm_gem_object *obj);
> +
> +	/**
> +	 * @export:
> +	 *
> +	 * Export backing buffer as a &dma_buf.
> +	 * If this is not set drm_gem_prime_export() is used.
> +	 *
> +	 * This callback is optional.
> +	 */
> +	struct dma_buf *(*export)(struct drm_gem_object *obj, int flags);
> +
> +	/*
> +	 * @pin:
> +	 *
> +	 * Pin backing buffer in memory.
> +	 *
> +	 * This callback is optional.
> +	 */
> +	int (*pin)(struct drm_gem_object *obj);
> +
> +	/*
> +	 * @unpin:
> +	 *
> +	 * Unpin backing buffer.
> +	 *
> +	 * This callback is optional.
> +	 */
> +	void (*unpin)(struct drm_gem_object *obj);
> +
> +	/*
> +	 * @get_sg_table:
> +	 *
> +	 * Returns a Scatter-Gather table representation of the buffer.
> +	 * Used when exporting a buffer.
> +	 *
> +	 * This callback is mandatory if buffer export is supported.
> +	 */
> +	struct sg_table *(*get_sg_table)(struct drm_gem_object *obj);
> +
> +	/*
> +	 * @vmap:
> +	 *
> +	 * Returns a virtual address for the buffer.
> +	 *
> +	 * This callback is optional.
> +	 */
> +	void *(*vmap)(struct drm_gem_object *obj);
> +
> +	/*
> +	 * @vunmap:
> +	 *
> +	 * Releases the the address previously returned by @vmap.
> +	 *
> +	 * This callback is optional.
> +	 */
> +	void (*vunmap)(struct drm_gem_object *obj, void *vaddr);
> +
> +	/*
> +	 * @mmap:
> +	 *
> +	 * Setup userspace mapping with the given vma.
> +	 *
> +	 * This callback is optional.
> +	 */
> +	int (*mmap)(struct drm_gem_object *obj, struct vm_area_struct *vma);
> +
> +	/**
> +	 * @vm_ops:
> +	 *
> +	 * Virtual memory operations used with mmap.
> +	 *
> +	 * This is optional but necessary for mmap support.
> +	 */
> +	const struct vm_operations_struct *vm_ops;
> +};

I think fleshing out the docs a bit is a good opportunity here (and adding
links to the old place that the new ones recommended). But probably best
in follow-up patches.

> +
>  /**
>   * struct drm_gem_object - GEM buffer object
>   *
> @@ -146,6 +270,15 @@ struct drm_gem_object {
>  	 * simply leave it as NULL.
>  	 */
>  	struct dma_buf_attachment *import_attach;
> +
> +	/*
> +	 * @funcs:
> +	 *
> +	 * Optional GEM object functions. If this is set, it will be used if the
> +	 * corresponding &drm_driver GEM callback is not set.

Maybe also here a note that this is recommended over the callbacks in
&drm_driver.

Aside from all the tiny style suggestions, I really like this.
-Daniel

> +	 *
> +	 */
> +	const struct drm_gem_object_funcs *funcs;
>  };
>  
>  /**
> @@ -293,4 +426,9 @@ int drm_gem_dumb_destroy(struct drm_file *file,
>  			 struct drm_device *dev,
>  			 uint32_t handle);
>  
> +int drm_gem_pin(struct drm_gem_object *obj);
> +void drm_gem_unpin(struct drm_gem_object *obj);
> +void *drm_gem_vmap(struct drm_gem_object *obj);
> +void drm_gem_vunmap(struct drm_gem_object *obj, void *vaddr);
> +
>  #endif /* __DRM_GEM_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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https://lists.freedesktop.org/mailman/listinfo/dri-devel




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