[RFC v2 7/8] drm/fb-helper: Add generic fbdev emulation

Noralf Trønnes
2018-01-03T22:21:09Z

Add generic fbdev emulation which uses a drm_file to get a dumb_buffer
and drm_framebuffer. The buffer is exported and vmap/mmap called on
the dma-buf.

Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
---
drivers/gpu/drm/drm_fb_helper.c | 301 +++++++++++++++++++++++++++++++++++++++-
include/drm/drm_fb_helper.h | 33 +++++
2 files changed, 333 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index f9dcc7a5761f..270ff6dc8045 100644
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -30,12 +30,15 @@
#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>
#include <linux/module.h>
#include <drm/drmP.h>
+#include <drm/drm_auth.h>
#include <drm/drm_crtc.h>
+#include <drm/drm_dumb_buffers.h>
#include <drm/drm_fb_helper.h>
#include <drm/drm_crtc_helper.h>
#include <drm/drm_atomic.h>
@@ -1951,7 +1954,9 @@ static int drm_fb_helper_single_fb_probe(struct drm_fb_helper *fb_helper,
if (fb_helper->fbdev->fbops->fb_open == drm_fb_helper_fb_open)
atomic_set(&fb_helper->open_count, 0);

- strcpy(fb_helper->fb->comm, "[fbcon]");
+ if (fb_helper->fb)
+ strcpy(fb_helper->fb->comm, "[fbcon]");
+
return 0;
}

@@ -2975,6 +2980,300 @@ void drm_fb_helper_output_poll_changed(struct drm_device *dev)
}
EXPORT_SYMBOL(drm_fb_helper_output_poll_changed);

+static struct fb_deferred_io drm_fb_helper_generic_defio = {
+ .delay = HZ / 20,
+ .deferred_io = drm_fb_helper_deferred_io,
+};
+
+static int drm_fb_helper_generic_alloc_buf(struct drm_fb_helper *fb_helper)
+{
+ struct drm_fb_helper_surface_size *sizes = &fb_helper->sizes;
+ struct drm_mode_create_dumb dumb_args = { 0 };
+ struct drm_prime_handle prime_args = { 0 };
+ struct drm_mode_fb_cmd2 fb_args = { 0 };
+ struct drm_device *dev = fb_helper->dev;
+ struct fb_info *fbi = fb_helper->fbdev;
+ struct drm_framebuffer *fb;
+ struct dma_buf *dma_buf;
+ struct drm_file *file;
+ void *vaddr;
+ int ret;
+
+ file = drm_file_alloc(dev->primary);
+ if (IS_ERR(file))
+ return PTR_ERR(file);
+
+ drm_dropmaster_ioctl(dev, NULL, file);
+
+ dumb_args.width = sizes->surface_width;
+ dumb_args.height = sizes->surface_height;
+ dumb_args.bpp = sizes->surface_bpp;
+ ret = drm_mode_create_dumb_ioctl(dev, &dumb_args, file);
+ if (ret)
+ goto err_free_file;
+
+ fb_args.width = dumb_args.width;
+ fb_args.height = dumb_args.height;
+ fb_args.pixel_format = drm_mode_legacy_fb_format(sizes->surface_bpp,
+ sizes->surface_depth);
+ fb_args.handles[0] = dumb_args.handle;
+ fb_args.pitches[0] = dumb_args.pitch;
+ ret = drm_mode_addfb2(dev, &fb_args, file);
+ if (ret)
+ goto err_free_file;
+
+ fb = drm_framebuffer_lookup(dev, file, fb_args.fb_id);
+ if (!fb) {
+ ret = -ENOENT;
+ goto err_free_file;
+ }
+
+ /* drop the reference we picked up in framebuffer lookup */
+ drm_framebuffer_put(fb);
+
+ strcpy(fb->comm, "[fbcon]");
+
+ prime_args.handle = dumb_args.handle;
+ ret = drm_prime_handle_to_fd_ioctl(dev, &prime_args, file);
+ if (ret)
+ goto err_free_file;
+
+ dma_buf = dma_buf_get(prime_args.fd);
+ if (WARN_ON(IS_ERR(dma_buf))) {
+ ret = PTR_ERR(dma_buf);
+ goto err_free_file;
+ }
+
+ vaddr = dma_buf_vmap(dma_buf);
+ if (!vaddr) {
+ ret = -ENOMEM;
+ goto err_put_dmabuf;
+ }
+
+ if (fb->funcs->dirty) {
+ fbi->fbdefio = &drm_fb_helper_generic_defio;
+ fb_deferred_io_init(fbi);
+ }
+
+ fbi->screen_size = fb->height * fb->pitches[0];
+ fbi->fix.smem_len = fbi->screen_size;
+ fbi->screen_buffer = vaddr;
+
+ fb_helper->dma_buf = dma_buf;
+ fb_helper->file = file;
+
+ mutex_lock(&fb_helper->lock);
+ fb_helper->fb = fb;
+ drm_setup_crtcs_fb(fb_helper);
+ mutex_unlock(&fb_helper->lock);
+
+ /* First time setup */
+ if (!fbi->var.bits_per_pixel) {
+ struct fb_videomode mode;
+
+ 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);
+
+ /* Drop the mode added by register_framebuffer() */
+ fb_destroy_modelist(&fb_helper->fbdev->modelist);
+
+ fb_var_to_videomode(&mode, &fbi->var);
+ fb_add_videomode(&mode, &fbi->modelist);
+ }
+
+ return 0;
+
+err_put_dmabuf:
+ dma_buf_put(dma_buf);
+err_free_file:
+ drm_file_free(file);
+
+ return ret;
+}
+
+static void drm_fb_helper_generic_free_buf(struct drm_fb_helper *fb_helper)
+{
+ mutex_lock(&fb_helper->lock);
+ fb_helper->fb = NULL;
+ drm_setup_crtcs_fb(fb_helper);
+ mutex_unlock(&fb_helper->lock);
+
+ if (fb_helper->fbdev->fbdefio) {
+ cancel_delayed_work_sync(&fb_helper->fbdev->deferred_work);
+ cancel_work_sync(&fb_helper->dirty_work);
+ fb_deferred_io_cleanup(fb_helper->fbdev);
+ }
+
+ dma_buf_vunmap(fb_helper->dma_buf, fb_helper->fbdev->screen_buffer);
+ dma_buf_put(fb_helper->dma_buf);
+ drm_file_free(fb_helper->file);
+
+ fb_helper->fbdev->screen_buffer = NULL;
+ fb_helper->dma_buf = NULL;
+ fb_helper->file = NULL;
+}
+
+static int drm_fb_helper_generic_fb_open(struct fb_info *info, int user)
+{
+ struct drm_fb_helper *fb_helper = info->par;
+ int ret;
+
+ ret = drm_fb_helper_fb_open(info, user);
+ if (ret)
+ return ret;
+
+ if (!fb_helper->fbdev->screen_buffer) {
+ /*
+ * Exporting a buffer to get a virtual address results in
+ * dma-buf pinning the driver module. This means that we have
+ * to defer this to open/close in order to unload the driver
+ * module.
+ */
+ ret = drm_fb_helper_generic_alloc_buf(fb_helper);
+ if (ret) {
+ DRM_ERROR("fbdev: Failed to allocate buffer: %d\n", ret);
+ drm_fb_helper_fb_release(info, user);
+ return ret;
+ }
+ }
+
+ return 0;
+}
+
+static int drm_fb_helper_generic_fb_release(struct fb_info *info, int user)
+{
+ struct drm_fb_helper *fb_helper = info->par;
+
+ drm_fb_helper_fb_release(info, user);
+
+ if (!atomic_read(&fb_helper->open_count))
+ drm_fb_helper_generic_free_buf(fb_helper);
+
+ return 0;
+}
+
+static int drm_fb_helper_generic_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->dma_buf, vma, 0);
+}
+
+static struct fb_ops drm_fb_helper_generic_fbdev_ops = {
+ .owner = THIS_MODULE,
+ DRM_FB_HELPER_DEFAULT_OPS,
+ .fb_open = drm_fb_helper_generic_fb_open,
+ .fb_release = drm_fb_helper_generic_fb_release,
+ .fb_mmap = drm_fb_helper_generic_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 int drm_fb_helper_generic_probe(struct drm_fb_helper *fb_helper,
+ struct drm_fb_helper_surface_size *sizes)
+{
+ struct fb_ops *fbops;
+ struct fb_info *fbi;
+
+ DRM_DEBUG_KMS("surface width(%d), height(%d) and bpp(%d)\n",
+ sizes->surface_width, sizes->surface_height,
+ sizes->surface_bpp);
+
+ fb_helper->sizes = *sizes;
+
+ /*
+ * fb_deferred_io_cleanup() clears &fbops->fb_mmap so a per instance
+ * version is necessary. We do it for all users since we don't know
+ * yet if the fb has a dirty callback. This also gives us the
+ * opportunity to set the correct owner.
+ */
+ fbops = kzalloc(sizeof(*fbops), GFP_KERNEL);
+ if (!fbops)
+ return -ENOMEM;
+
+ *fbops = drm_fb_helper_generic_fbdev_ops;
+ fbops->owner = fb_helper->dev->driver->fops->owner;
+
+ fbi = drm_fb_helper_alloc_fbi(fb_helper);
+ if (IS_ERR(fbi)) {
+ kfree(fbops);
+ return PTR_ERR(fbi);
+ }
+
+ fbi->par = fb_helper;
+ fbi->fbops = fbops;
+ strcpy(fbi->fix.id, "generic");
+
+ /* The rest of the setup is deferred to fb_open */
+
+ atomic_set(&fb_helper->open_count, 0);
+
+ return 0;
+}
+
+static void drm_fb_helper_generic_release(struct drm_fb_helper *fb_helper)
+{
+ struct fb_ops *fbops = fb_helper->fbdev->fbops;
+
+ drm_fb_helper_fini(fb_helper);
+ kfree(fb_helper);
+ kfree(fbops);
+}
+
+static const struct drm_fb_helper_funcs drm_fb_helper_generic_funcs = {
+ .fb_probe = drm_fb_helper_generic_probe,
+ .restore = drm_fb_helper_restore_fbdev_mode_unlocked,
+ .hotplug_event = drm_fb_helper_hotplug_event,
+ .unregister = drm_fb_helper_unregister_fbi,
+ .release = drm_fb_helper_generic_release,
+};
+
+/**
+ * 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.
+ * @max_conn_count: Maximum number of connectors.
+ * @dev->mode_config.num_connector is used if this is zero.
+ *
+ * This function sets up generic fbdev emulation for drivers that supports
+ * dumb buffers which can be exported. The driver doesn't have to do anything
+ * else than to call this function, restore, hotplug events and teardown are
+ * all taken care of.
+ *
+ * Returns:
+ * Zero on success or negative error code on failure.
+ */
+int drm_fb_helper_generic_fbdev_setup(struct drm_device *dev,
+ unsigned int preferred_bpp,
+ unsigned int max_conn_count)
+{
+ struct drm_fb_helper *fb_helper;
+ int ret;
+
+ if (!drm_fbdev_emulation)
+ return 0;
+
+ fb_helper = kzalloc(sizeof(*fb_helper), GFP_KERNEL);
+ if (!fb_helper)
+ return -ENOMEM;
+
+ ret = drm_fb_helper_fbdev_setup(dev, fb_helper,
+ &drm_fb_helper_generic_funcs,
+ preferred_bpp, max_conn_count);
+ if (ret) {
+ kfree(fb_helper);
+ return ret;
+ }
+
+ return 0;
+}
+EXPORT_SYMBOL(drm_fb_helper_generic_fbdev_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 385f967c3552..c6940ab6ffac 100644
--- a/include/drm/drm_fb_helper.h
+++ b/include/drm/drm_fb_helper.h
@@ -279,6 +279,28 @@ struct drm_fb_helper {
* initial value to 0 themselves.
*/
atomic_t open_count;
+
+ /**
+ * @file:
+ *
+ * Optional DRM file. Used by the generic fbdev code.
+ */
+ struct drm_file *file;
+
+ /**
+ * @dma_buf:
+ *
+ * Optional pointer to a DMA buffer object.
+ * Used by the generic fbdev code.
+ */
+ struct dma_buf *dma_buf;
+
+ /**
+ * @sizes:
+ *
+ * Optional surface sizes. Used by the generic fbdev code.
+ */
+ struct drm_fb_helper_surface_size sizes;
};

/**
@@ -380,6 +402,10 @@ 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);
+
+int drm_fb_helper_generic_fbdev_setup(struct drm_device *dev,
+ unsigned int preferred_bpp,
+ unsigned int max_conn_count);
#else
static inline void drm_fb_helper_prepare(struct drm_device *dev,
struct drm_fb_helper *helper,
@@ -624,6 +650,13 @@ static inline void drm_fb_helper_output_poll_changed(struct drm_device *dev)
{
}

+static inline int
+drm_fb_helper_generic_fbdev_setup(struct drm_device *dev,
+ unsigned int preferred_bpp,
+ unsigned int max_conn_count)
+{
+ return 0;
+}
#endif

static inline int
--
2.14.2