[PATCH 5/6] drm/msm: fbdev: Use a DRM client buffer

Thomas Zimmermann
2026-04-21T12:57:54Z

Replace the internal DRM framebuffer with a DRM client buffer. The
client buffer allocates the DRM framebuffer on a file and also uses
GEM object handles via the regular ADDFB2 interfaces.

Using client-buffer interfaces unifies framebuffer allocation for
DRM clients in user space and msm's internal fbdev emulation. It
also simplifies the clean-up side of the fbdev emulation.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
---
drivers/gpu/drm/msm/msm_fbdev.c | 55 +++++++++++++++++++--------------
1 file changed, 32 insertions(+), 23 deletions(-)

diff --git a/drivers/gpu/drm/msm/msm_fbdev.c b/drivers/gpu/drm/msm/msm_fbdev.c
index 5532c5779f17..f14db46aa51e 100644
--- a/drivers/gpu/drm/msm/msm_fbdev.c
+++ b/drivers/gpu/drm/msm/msm_fbdev.c
@@ -41,17 +41,15 @@ static int msm_fbdev_mmap(struct fb_info *info, struct vm_area_struct *vma)
static void msm_fbdev_fb_destroy(struct fb_info *info)
{
struct drm_fb_helper *helper = (struct drm_fb_helper *)info->par;
- struct drm_framebuffer *fb = helper->fb;
- struct drm_gem_object *bo = msm_framebuffer_bo(fb, 0);
+ struct drm_gem_object *bo = msm_framebuffer_bo(helper->fb, 0);

DBG();

drm_fb_helper_fini(helper);

- /* this will free the backing object */
msm_gem_put_vaddr(bo);
- drm_framebuffer_remove(fb);

+ drm_client_buffer_delete(helper->buffer);
drm_client_release(&helper->client);
}

@@ -90,15 +88,16 @@ static const struct drm_fb_helper_funcs msm_fbdev_helper_funcs = {
int msm_fbdev_driver_fbdev_probe(struct drm_fb_helper *helper,
struct drm_fb_helper_surface_size *sizes)
{
- struct drm_device *dev = helper->dev;
+ struct drm_client_dev *client = &helper->client;
+ struct drm_device *dev = client->dev;
+ struct drm_file *file = client->file;
struct msm_drm_private *priv = dev->dev_private;
struct fb_info *fbi = helper->info;
- struct drm_mode_fb_cmd2 mode_cmd = { };
- struct drm_framebuffer *fb = NULL;
const struct drm_format_info *format;
- u32 fourcc, pitch;
+ u32 fourcc, pitch, handle;
u64 size;
struct drm_gem_object *bo;
+ struct drm_client_buffer *buffer;
uint64_t paddr;
int ret;

@@ -127,16 +126,15 @@ int msm_fbdev_driver_fbdev_probe(struct drm_fb_helper *helper,

msm_gem_object_set_name(bo, "stolenfb");

- mode_cmd.pixel_format = fourcc;
- mode_cmd.width = sizes->surface_width;
- mode_cmd.height = sizes->surface_height;
- mode_cmd.pitches[0] = pitch;
-
- fb = msm_framebuffer_init(dev, format, &mode_cmd, &bo);
- if (IS_ERR(fb)) {
- drm_err(dev, "failed to allocate fb\n");
- ret = PTR_ERR(fb);
+ ret = drm_gem_handle_create(file, bo, &handle);
+ if (ret)
goto err_drm_gem_object_put;
+
+ buffer = drm_client_buffer_create(client, sizes->surface_width, sizes->surface_height,
+ fourcc, handle, pitch);
+ if (IS_ERR(buffer)) {
+ ret = PTR_ERR(buffer);
+ goto err_drm_gem_handle_delete;
}

/*
@@ -147,13 +145,14 @@ int msm_fbdev_driver_fbdev_probe(struct drm_fb_helper *helper,
ret = msm_gem_get_and_pin_iova(bo, priv->kms->vm, &paddr);
if (ret) {
drm_err(dev, "failed to get buffer obj iova: %d\n", ret);
- goto err_drm_framebuffer_remove;
+ goto err_drm_client_buffer_delete;
}

DBG("fbi=%p, dev=%p", fbi, dev);

helper->funcs = &msm_fbdev_helper_funcs;
- helper->fb = fb;
+ helper->buffer = buffer;
+ helper->fb = buffer->fb;

fbi->fbops = &msm_fb_ops;

@@ -162,19 +161,29 @@ int msm_fbdev_driver_fbdev_probe(struct drm_fb_helper *helper,
fbi->screen_buffer = msm_gem_get_vaddr(bo);
if (IS_ERR(fbi->screen_buffer)) {
ret = PTR_ERR(fbi->screen_buffer);
- goto err_drm_framebuffer_remove;
+ goto err_msm_gem_put_vaddr;
}
fbi->screen_size = bo->size;
fbi->fix.smem_start = paddr;
fbi->fix.smem_len = bo->size;

DBG("par=%p, %dx%d", fbi->par, fbi->var.xres, fbi->var.yres);
- DBG("allocated %dx%d fb", fb->width, fb->height);
+ DBG("allocated %dx%d fb", buffer->fb->width, buffer->fb->height);
+
+ /* The handle is only needed for creating the framebuffer. */
+ drm_gem_handle_delete(file, handle);
+
+ /* The framebuffer still holds a reference on the GEM object. */
+ drm_gem_object_put(bo);

return 0;

-err_drm_framebuffer_remove:
- drm_framebuffer_remove(fb);
+err_msm_gem_put_vaddr:
+ msm_gem_put_vaddr(bo);
+err_drm_client_buffer_delete:
+ drm_client_buffer_delete(buffer);
+err_drm_gem_handle_delete:
+ drm_gem_handle_delete(file, handle);
err_drm_gem_object_put:
drm_gem_object_put(bo);
return ret;
--
2.53.0