Re: [RFC v4 22/25] drm/fb-helper: Add generic fbdev emulation

[Daniel Vetter <daniel@ffwll.ch>]

On Sat, Apr 14, 2018 at 01:53:15PM +0200, Noralf Trønnes wrote:
> This adds generic fbdev emulation for drivers that supports
> dumb buffers which they can export.
> 
> All the driver has to do is call drm_fbdev_generic_setup().
> 
> Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
> ---
>  drivers/gpu/drm/drm_fb_helper.c | 255 ++++++++++++++++++++++++++++++++++++++++
>  include/drm/drm_fb_helper.h     |  20 ++++
>  2 files changed, 275 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
> index b1124c08b1ed..1954de5b13e0 100644
> --- a/drivers/gpu/drm/drm_fb_helper.c
> +++ b/drivers/gpu/drm/drm_fb_helper.c
> @@ -30,6 +30,7 @@
>  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
>  
>  #include <linux/console.h>
> +#include <linux/dma-buf.h>
>  #include <linux/kernel.h>
>  #include <linux/sysrq.h>
>  #include <linux/slab.h>
> @@ -1995,6 +1996,260 @@ void drm_fb_helper_output_poll_changed(struct drm_device *dev)
>  }
>  EXPORT_SYMBOL(drm_fb_helper_output_poll_changed);
>  
> +static int drm_fbdev_fb_mmap(struct fb_info *info, struct vm_area_struct *vma)
> +{
> +	struct drm_fb_helper *fb_helper = info->par;
> +
> +	return dma_buf_mmap(fb_helper->buffer->dma_buf, vma, 0);
> +}
> +
> +/*
> + * fb_ops.fb_destroy is called by the last put_fb_info() call at the end of
> + * unregister_framebuffer() or fb_release().
> + */
> +static void drm_fbdev_fb_destroy(struct fb_info *info)
> +{
> +	struct drm_fb_helper *fb_helper = info->par;
> +	struct fb_ops *fbops = NULL;
> +
> +	DRM_DEBUG("\n");
> +
> +	if (fb_helper->fbdev->fbdefio)
> +		fbops = fb_helper->fbdev->fbops;
> +
> +	drm_fb_helper_fini(fb_helper);
> +	drm_client_framebuffer_delete(fb_helper->buffer);
> +	drm_client_free(fb_helper->client);
> +	kfree(fb_helper);
> +	kfree(fbops);
> +}
> +
> +static struct fb_ops drm_fbdev_fb_ops = {
> +	/*
> +	 * No need to set owner, this module is already pinned by the driver.
> +	 * A reference is taken on the driver module in drm_fb_helper_fb_open()
> +	 * to prevent the driver going away with open fd's.
> +	 */
> +	DRM_FB_HELPER_DEFAULT_OPS,
> +	.fb_open	= drm_fb_helper_fb_open,
> +	.fb_release	= drm_fb_helper_fb_release,
> +	.fb_destroy	= drm_fbdev_fb_destroy,
> +	.fb_mmap	= drm_fbdev_fb_mmap,
> +	.fb_read	= drm_fb_helper_sys_read,
> +	.fb_write	= drm_fb_helper_sys_write,
> +	.fb_fillrect	= drm_fb_helper_sys_fillrect,
> +	.fb_copyarea	= drm_fb_helper_sys_copyarea,
> +	.fb_imageblit	= drm_fb_helper_sys_imageblit,
> +};
> +
> +static struct fb_deferred_io drm_fbdev_defio = {
> +	.delay		= HZ / 20,
> +	.deferred_io	= drm_fb_helper_deferred_io,
> +};
> +
> +/* Hack to test tinydrm before converting to vmalloc buffers */
> +static int drm_fbdev_cma_deferred_io_mmap(struct fb_info *info,
> +					  struct vm_area_struct *vma)
> +{
> +	fb_deferred_io_mmap(info, vma);
> +	vma->vm_page_prot = pgprot_writecombine(vma->vm_page_prot);
> +
> +	return 0;
> +}
> +
> +static int drm_fb_helper_generic_probe(struct drm_fb_helper *fb_helper,
> +				       struct drm_fb_helper_surface_size *sizes)
> +{
> +	struct drm_client_dev *client = fb_helper->client;
> +	struct drm_display_mode sizes_mode = {
> +		.hdisplay = sizes->surface_width,
> +		.vdisplay = sizes->surface_height,
> +	};
> +	struct drm_client_buffer *buffer;
> +	struct drm_framebuffer *fb;
> +	struct fb_info *fbi;
> +	u32 format;
> +	int ret;
> +
> +	DRM_DEBUG_KMS("surface width(%d), height(%d) and bpp(%d)\n",
> +		      sizes->surface_width, sizes->surface_height,
> +		      sizes->surface_bpp);
> +
> +	format = drm_mode_legacy_fb_format(sizes->surface_bpp, sizes->surface_depth);
> +	buffer = drm_client_framebuffer_create(client, &sizes_mode, format);
> +	if (IS_ERR(buffer))
> +		return PTR_ERR(buffer);
> +
> +	fb_helper->buffer = buffer;
> +	fb_helper->fb = buffer->fb;
> +	fb = buffer->fb;
> +
> +	fbi = drm_fb_helper_alloc_fbi(fb_helper);
> +	if (IS_ERR(fbi)) {
> +		ret = PTR_ERR(fbi);
> +		goto err_free_buffer;
> +	}
> +
> +	fbi->par = fb_helper;
> +	fbi->fbops = &drm_fbdev_fb_ops;
> +	fbi->screen_size = fb->height * fb->pitches[0];
> +	fbi->fix.smem_len = fbi->screen_size;
> +	fbi->screen_buffer = buffer->vaddr;
> +	strcpy(fbi->fix.id, "DRM emulated");
> +
> +	drm_fb_helper_fill_fix(fbi, fb->pitches[0], fb->format->depth);
> +	drm_fb_helper_fill_var(fbi, fb_helper, sizes->fb_width, sizes->fb_height);
> +
> +	/*
> +	 * Drivers that set the dirty callback:
> +	 * - Doesn't use defio:
> +	 *   i915, virtio, rockchip
> +	 * - defio with vmalloc buffer blitted on the real one:
> +	 *   vmwgfx
> +	 * - defio is disabled because it doesn't work with shmem:
> +	 *   udl
> +	 * - defio with special dirty callback for fbdev, uses vmalloc for fbdev:
> +	 *   qxl
> +	 * - defio with cma buffer, will move to vmalloc buffers:
> +	 *   tinydrm
> +	 *
> +	 * TODO:
> +	 * Maybe add vmalloc shadow buffer support.
> +	 */
> +
> +	if (fb->funcs->dirty) {
> +		struct fb_ops *fbops;
> +
> +		/*
> +		 * fb_deferred_io_cleanup() clears &fbops->fb_mmap so a per
> +		 * instance version is necessary.
> +		 */
> +		fbops = kzalloc(sizeof(*fbops), GFP_KERNEL);
> +		if (!fbops) {
> +			ret = -ENOMEM;
> +			goto err_fb_info_destroy;
> +		}
> +
> +		*fbops = *fbi->fbops;
> +		fbi->fbops = fbops;
> +
> +		fbi->fbdefio = &drm_fbdev_defio;
> +
> +		/* Hack so I can test with tinydrm */
> +		fbi->fix.smem_start = page_to_phys(virt_to_page(buffer->vaddr));
> +
> +		fb_deferred_io_init(fbi);
> +
> +		/* Hack so I can test with tinydrm */
> +		fbi->fbops->fb_mmap = drm_fbdev_cma_deferred_io_mmap;
> +	}
> +
> +	return 0;
> +
> +err_fb_info_destroy:
> +	drm_fb_helper_fini(fb_helper);
> +err_free_buffer:
> +	drm_client_framebuffer_delete(buffer);
> +
> +	return ret;
> +}

I'd split this patch into 2:

- First one just adds the generic_probe callback. We could then start
  rolling that one out to lots of drivers, which would give all this code
  lots of testing.

- Second part is the generic client stuff below. Again then with follow-up
  patches to roll it out.

This way we could achieve a slightly more gradual transition of drivers.
And the first step should only be replacing the fb_probe callback.
-Daniel


> +
> +static const struct drm_fb_helper_funcs drm_fb_helper_generic_funcs = {
> +	.fb_probe = drm_fb_helper_generic_probe,
> +};
> +
> +static int drm_fbdev_client_remove(struct drm_client_dev *client)
> +{
> +	struct drm_fb_helper *fb_helper = client->private;
> +
> +	if (!fb_helper->fbdev) {
> +		kfree(fb_helper);
> +		return 0;
> +	}
> +
> +	unregister_framebuffer(fb_helper->fbdev);
> +
> +	/*
> +	 * If userspace is closed the client is now freed by
> +	 * drm_fbdev_fb_destroy(), otherwise it will be freed on the last close.
> +	 * Return 1 to tell that freeing is taken care of.
> +	 */
> +
> +	return 1;
> +}
> +
> +static int drm_fbdev_client_lastclose(struct drm_client_dev *client)
> +{
> +	struct drm_fb_helper *fb_helper = client->private;
> +
> +	drm_fb_helper_restore_fbdev_mode_unlocked(fb_helper);
> +
> +	return 0;
> +}
> +
> +static int drm_fbdev_client_hotplug(struct drm_client_dev *client)
> +{
> +	struct drm_fb_helper *fb_helper = client->private;
> +
> +	if (fb_helper->fbdev)
> +		return 0;
> +
> +	return drm_fb_helper_fbdev_setup(client->dev, fb_helper,
> +					 &drm_fb_helper_generic_funcs,
> +					 fb_helper->preferred_bpp, 0);
> +}
> +
> +static const struct drm_client_funcs drm_fbdev_client_funcs = {
> +	.name		= "fbdev",
> +	.remove		= drm_fbdev_client_remove,
> +	.lastclose	= drm_fbdev_client_lastclose,
> +	.hotplug	= drm_fbdev_client_hotplug,
> +};
> +
> +/**
> + * drm_fb_helper_generic_fbdev_setup() - Setup generic fbdev emulation
> + * @dev: DRM device
> + * @preferred_bpp: Preferred bits per pixel for the device.
> + *                 @dev->mode_config.preferred_depth is used if this is zero.
> + *
> + * This function sets up generic fbdev emulation for drivers that supports
> + * dumb buffers which can be exported.
> + *
> + * Restore, hotplug events and teardown are all taken care of. Drivers that does
> + * suspend/resume need to call drm_fb_helper_set_suspend_unlocked() themselves.
> + * Simple drivers might use drm_mode_config_helper_suspend().
> + *
> + * Returns:
> + * Zero on success or negative error code on failure.
> + */
> +int drm_fbdev_generic_setup(struct drm_device *dev, unsigned int preferred_bpp)
> +{
> +	struct drm_fb_helper *fb_helper;
> +	struct drm_client_dev *client;
> +
> +	if (!drm_fbdev_emulation)
> +		return 0;
> +
> +	fb_helper = kzalloc(sizeof(*fb_helper), GFP_KERNEL);
> +	if (!fb_helper)
> +		return -ENOMEM;
> +
> +	client = drm_client_new(dev, &drm_fbdev_client_funcs);
> +	if (IS_ERR(client)) {
> +		kfree(fb_helper);
> +		return PTR_ERR(client);
> +	}
> +
> +	client->private = fb_helper;
> +	fb_helper->client = client;
> +	fb_helper->preferred_bpp = preferred_bpp;
> +
> +	drm_fbdev_client_hotplug(client);
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL(drm_fbdev_generic_setup);
> +
>  /* The Kconfig DRM_KMS_HELPER selects FRAMEBUFFER_CONSOLE (if !EXPERT)
>   * but the module doesn't depend on any fb console symbols.  At least
>   * attempt to load fbcon to avoid leaving the system without a usable console.
> diff --git a/include/drm/drm_fb_helper.h b/include/drm/drm_fb_helper.h
> index 330983975d5e..711da1747836 100644
> --- a/include/drm/drm_fb_helper.h
> +++ b/include/drm/drm_fb_helper.h
> @@ -126,6 +126,20 @@ struct drm_fb_helper {
>  	 */
>  	struct drm_client_display *display;
>  
> +	/**
> +	 * @client:
> +	 *
> +	 * DRM client used by the generic fbdev emulation.
> +	 */
> +	struct drm_client_dev *client;
> +
> +	/**
> +	 * @buffer:
> +	 *
> +	 * Framebuffer used by the generic fbdev emulation.
> +	 */
> +	struct drm_client_buffer *buffer;
> +
>  	const struct drm_fb_helper_funcs *funcs;
>  	struct fb_info *fbdev;
>  	u32 pseudo_palette[17];
> @@ -219,6 +233,7 @@ struct drm_fb_helper {
>  	.fb_ioctl	= drm_fb_helper_ioctl
>  
>  #ifdef CONFIG_DRM_FBDEV_EMULATION
> +int drm_fbdev_generic_setup(struct drm_device *dev, unsigned int preferred_bpp);
>  void drm_fb_helper_prepare(struct drm_device *dev, struct drm_fb_helper *helper,
>  			   const struct drm_fb_helper_funcs *funcs);
>  int drm_fb_helper_init(struct drm_device *dev,
> @@ -297,6 +312,11 @@ void drm_fb_helper_fbdev_teardown(struct drm_device *dev);
>  void drm_fb_helper_lastclose(struct drm_device *dev);
>  void drm_fb_helper_output_poll_changed(struct drm_device *dev);
>  #else
> +static inline int
> +drm_fbdev_generic_setup(struct drm_device *dev, unsigned int preferred_bpp)
> +{
> +}
> +
>  static inline void drm_fb_helper_prepare(struct drm_device *dev,
>  					struct drm_fb_helper *helper,
>  					const struct drm_fb_helper_funcs *funcs)
> -- 
> 2.15.1
> 
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
_______________________________________________
Intel-gfx mailing list
Intel-gfx@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/intel-gfx