From: Sasha Levin <sashal@kernel.org>
To: stable@vger.kernel.org
Cc: Thomas Zimmermann <tzimmermann@suse.de>,
Javier Martinez Canillas <javierm@redhat.com>,
Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.15.y 1/6] fbdev: Put mmap for deferred I/O into drivers
Date: Mon, 7 Sep 2026 21:18:10 -0400 [thread overview]
Message-ID: <20260908011815.1729727-1-sashal@kernel.org> (raw)
In-Reply-To: <2026090351-mantra-reunion-82ab@gregkh>
From: Thomas Zimmermann <tzimmermann@suse.de>
[ Upstream commit 5905585103276b7c14bb9a7de4b575216cb6dac4 ]
The fbdev mmap function fb_mmap() unconditionally overrides the
driver's implementation if deferred I/O has been activated. This
makes it hard to implement mmap with anything but a vmalloc()'ed
software buffer. That is specifically a problem for DRM, where
video memory is maintained by a memory manager.
Leave the mmap handling to drivers and expect them to call the
helper for deferred I/O by thmeselves.
v4:
* unlock mm_lock in fb_mmap() error path (Dan)
v3:
* fix warning if fb_mmap is missing (kernel test robot)
v2:
* print a helpful error message if the defio setup is
incorrect (Javier)
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220429100834.18898-2-tzimmermann@suse.de
Stable-dep-of: 9ad709afdfa3 ("fbdev: ssd1307fb: defer I2C transfers from damage callbacks")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/gpu/drm/drm_fb_helper.c | 4 +++-
drivers/gpu/drm/vmwgfx/vmwgfx_fb.c | 1 +
drivers/hid/hid-picolcd_fb.c | 1 +
drivers/staging/fbtft/fbtft-core.c | 1 +
drivers/video/fbdev/broadsheetfb.c | 1 +
drivers/video/fbdev/core/fb_defio.c | 1 +
drivers/video/fbdev/core/fbmem.c | 22 ++++++++++++----------
drivers/video/fbdev/hecubafb.c | 1 +
drivers/video/fbdev/hyperv_fb.c | 1 +
drivers/video/fbdev/metronomefb.c | 1 +
drivers/video/fbdev/sh_mobile_lcdcfb.c | 6 ++++++
drivers/video/fbdev/smscufx.c | 3 +++
drivers/video/fbdev/ssd1307fb.c | 1 +
drivers/video/fbdev/udlfb.c | 3 +++
drivers/video/fbdev/xen-fbfront.c | 1 +
15 files changed, 37 insertions(+), 11 deletions(-)
diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index bc265aa0f692b..7dc10cb90d4e5 100644
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -2090,7 +2090,9 @@ static int drm_fbdev_fb_mmap(struct fb_info *info, struct vm_area_struct *vma)
{
struct drm_fb_helper *fb_helper = info->par;
- if (fb_helper->dev->driver->gem_prime_mmap)
+ if (drm_fbdev_use_shadow_fb(fb_helper))
+ return fb_deferred_io_mmap(info, vma);
+ else if (fb_helper->dev->driver->gem_prime_mmap)
return fb_helper->dev->driver->gem_prime_mmap(fb_helper->buffer->gem, vma);
else
return -ENODEV;
diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_fb.c b/drivers/gpu/drm/vmwgfx/vmwgfx_fb.c
index 79b08e927f769..8c1e9205937d1 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_fb.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_fb.c
@@ -626,6 +626,7 @@ static const struct fb_ops vmw_fb_ops = {
.fb_imageblit = vmw_fb_imageblit,
.fb_pan_display = vmw_fb_pan_display,
.fb_blank = vmw_fb_blank,
+ .fb_mmap = fb_deferred_io_mmap,
};
int vmw_fb_init(struct vmw_private *vmw_priv)
diff --git a/drivers/hid/hid-picolcd_fb.c b/drivers/hid/hid-picolcd_fb.c
index 8a0d1365cd723..de61c08fabea9 100644
--- a/drivers/hid/hid-picolcd_fb.c
+++ b/drivers/hid/hid-picolcd_fb.c
@@ -428,6 +428,7 @@ static const struct fb_ops picolcdfb_ops = {
.fb_imageblit = picolcd_fb_imageblit,
.fb_check_var = picolcd_fb_check_var,
.fb_set_par = picolcd_set_par,
+ .fb_mmap = fb_deferred_io_mmap,
};
diff --git a/drivers/staging/fbtft/fbtft-core.c b/drivers/staging/fbtft/fbtft-core.c
index 67604a4d9a39f..0e5b3f627fff2 100644
--- a/drivers/staging/fbtft/fbtft-core.c
+++ b/drivers/staging/fbtft/fbtft-core.c
@@ -653,6 +653,7 @@ struct fb_info *fbtft_framebuffer_alloc(struct fbtft_display *display,
fbops->fb_imageblit = fbtft_fb_imageblit;
fbops->fb_setcolreg = fbtft_fb_setcolreg;
fbops->fb_blank = fbtft_fb_blank;
+ fbops->fb_mmap = fb_deferred_io_mmap;
fbdefio->delay = HZ / fps;
fbdefio->sort_pagereflist = true;
diff --git a/drivers/video/fbdev/broadsheetfb.c b/drivers/video/fbdev/broadsheetfb.c
index 786fe6116405b..fd66e18fd58a5 100644
--- a/drivers/video/fbdev/broadsheetfb.c
+++ b/drivers/video/fbdev/broadsheetfb.c
@@ -1054,6 +1054,7 @@ static const struct fb_ops broadsheetfb_ops = {
.fb_fillrect = broadsheetfb_fillrect,
.fb_copyarea = broadsheetfb_copyarea,
.fb_imageblit = broadsheetfb_imageblit,
+ .fb_mmap = fb_deferred_io_mmap,
};
static struct fb_deferred_io broadsheetfb_defio = {
diff --git a/drivers/video/fbdev/core/fb_defio.c b/drivers/video/fbdev/core/fb_defio.c
index e348f4c15d81a..20f3f9c5242b1 100644
--- a/drivers/video/fbdev/core/fb_defio.c
+++ b/drivers/video/fbdev/core/fb_defio.c
@@ -321,6 +321,7 @@ int fb_deferred_io_mmap(struct fb_info *info, struct vm_area_struct *vma)
return 0;
}
+EXPORT_SYMBOL_GPL(fb_deferred_io_mmap);
/* workqueue callback */
static void fb_deferred_io_work(struct work_struct *work)
diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c
index 130fa827eee32..78303cf740701 100644
--- a/drivers/video/fbdev/core/fbmem.c
+++ b/drivers/video/fbdev/core/fbmem.c
@@ -1352,7 +1352,6 @@ static int
fb_mmap(struct file *file, struct vm_area_struct * vma)
{
struct fb_info *info = file_fb_info(file);
- int (*fb_mmap_fn)(struct fb_info *info, struct vm_area_struct *vma);
unsigned long mmio_pgoff;
unsigned long start;
u32 len;
@@ -1361,14 +1360,7 @@ fb_mmap(struct file *file, struct vm_area_struct * vma)
return -ENODEV;
mutex_lock(&info->mm_lock);
- fb_mmap_fn = info->fbops->fb_mmap;
-
-#if IS_ENABLED(CONFIG_FB_DEFERRED_IO)
- if (info->fbdefio)
- fb_mmap_fn = fb_deferred_io_mmap;
-#endif
-
- if (fb_mmap_fn) {
+ if (info->fbops->fb_mmap) {
int res;
/*
@@ -1376,9 +1368,19 @@ fb_mmap(struct file *file, struct vm_area_struct * vma)
* SME protection is removed ahead of the call
*/
vma->vm_page_prot = pgprot_decrypted(vma->vm_page_prot);
- res = fb_mmap_fn(info, vma);
+ res = info->fbops->fb_mmap(info, vma);
mutex_unlock(&info->mm_lock);
return res;
+#if IS_ENABLED(CONFIG_FB_DEFERRED_IO)
+ } else if (info->fbdefio) {
+ /*
+ * FB deferred I/O wants you to handle mmap in your drivers. At a
+ * minimum, point struct fb_ops.fb_mmap to fb_deferred_io_mmap().
+ */
+ dev_warn_once(info->dev, "fbdev mmap not set up for deferred I/O.\n");
+ mutex_unlock(&info->mm_lock);
+ return -ENODEV;
+#endif
}
/*
diff --git a/drivers/video/fbdev/hecubafb.c b/drivers/video/fbdev/hecubafb.c
index 3c3cd45c1908f..962a155a5b3d0 100644
--- a/drivers/video/fbdev/hecubafb.c
+++ b/drivers/video/fbdev/hecubafb.c
@@ -203,6 +203,7 @@ static const struct fb_ops hecubafb_ops = {
.fb_fillrect = hecubafb_fillrect,
.fb_copyarea = hecubafb_copyarea,
.fb_imageblit = hecubafb_imageblit,
+ .fb_mmap = fb_deferred_io_mmap,
};
static struct fb_deferred_io hecubafb_defio = {
diff --git a/drivers/video/fbdev/hyperv_fb.c b/drivers/video/fbdev/hyperv_fb.c
index 5fd1b33d11238..ccc2e41275dd0 100644
--- a/drivers/video/fbdev/hyperv_fb.c
+++ b/drivers/video/fbdev/hyperv_fb.c
@@ -915,6 +915,7 @@ static const struct fb_ops hvfb_ops = {
.fb_copyarea = hvfb_cfb_copyarea,
.fb_imageblit = hvfb_cfb_imageblit,
.fb_blank = hvfb_blank,
+ .fb_mmap = fb_deferred_io_mmap,
};
diff --git a/drivers/video/fbdev/metronomefb.c b/drivers/video/fbdev/metronomefb.c
index f79f8cc41f33b..ed73769f2ecdb 100644
--- a/drivers/video/fbdev/metronomefb.c
+++ b/drivers/video/fbdev/metronomefb.c
@@ -563,6 +563,7 @@ static const struct fb_ops metronomefb_ops = {
.fb_fillrect = metronomefb_fillrect,
.fb_copyarea = metronomefb_copyarea,
.fb_imageblit = metronomefb_imageblit,
+ .fb_mmap = fb_deferred_io_mmap,
};
static struct fb_deferred_io metronomefb_defio = {
diff --git a/drivers/video/fbdev/sh_mobile_lcdcfb.c b/drivers/video/fbdev/sh_mobile_lcdcfb.c
index 74a013c398b14..91a5803b2ebde 100644
--- a/drivers/video/fbdev/sh_mobile_lcdcfb.c
+++ b/drivers/video/fbdev/sh_mobile_lcdcfb.c
@@ -1483,6 +1483,9 @@ sh_mobile_lcdc_overlay_mmap(struct fb_info *info, struct vm_area_struct *vma)
{
struct sh_mobile_lcdc_overlay *ovl = info->par;
+ if (info->fbdefio)
+ return fb_deferred_io_mmap(info, vma);
+
return dma_mmap_coherent(ovl->channel->lcdc->dev, vma, ovl->fb_mem,
ovl->dma_handle, ovl->fb_size);
}
@@ -1957,6 +1960,9 @@ sh_mobile_lcdc_mmap(struct fb_info *info, struct vm_area_struct *vma)
{
struct sh_mobile_lcdc_chan *ch = info->par;
+ if (info->fbdefio)
+ return fb_deferred_io_mmap(info, vma);
+
return dma_mmap_coherent(ch->lcdc->dev, vma, ch->fb_mem,
ch->dma_handle, ch->fb_size);
}
diff --git a/drivers/video/fbdev/smscufx.c b/drivers/video/fbdev/smscufx.c
index 071448eba2465..61c1556bf7c5f 100644
--- a/drivers/video/fbdev/smscufx.c
+++ b/drivers/video/fbdev/smscufx.c
@@ -780,6 +780,9 @@ static int ufx_ops_mmap(struct fb_info *info, struct vm_area_struct *vma)
unsigned long offset = vma->vm_pgoff << PAGE_SHIFT;
unsigned long page, pos;
+ if (info->fbdefio)
+ return fb_deferred_io_mmap(info, vma);
+
if (vma->vm_pgoff > (~0UL >> PAGE_SHIFT))
return -EINVAL;
if (size > info->fix.smem_len)
diff --git a/drivers/video/fbdev/ssd1307fb.c b/drivers/video/fbdev/ssd1307fb.c
index 212494b0a4ba8..1604529a565d9 100644
--- a/drivers/video/fbdev/ssd1307fb.c
+++ b/drivers/video/fbdev/ssd1307fb.c
@@ -368,6 +368,7 @@ static const struct fb_ops ssd1307fb_ops = {
.fb_fillrect = ssd1307fb_fillrect,
.fb_copyarea = ssd1307fb_copyarea,
.fb_imageblit = ssd1307fb_imageblit,
+ .fb_mmap = fb_deferred_io_mmap,
};
static void ssd1307fb_deferred_io(struct fb_info *info, struct list_head *pagereflist)
diff --git a/drivers/video/fbdev/udlfb.c b/drivers/video/fbdev/udlfb.c
index 3c17049de9540..a16cf3bd6a9a4 100644
--- a/drivers/video/fbdev/udlfb.c
+++ b/drivers/video/fbdev/udlfb.c
@@ -348,6 +348,9 @@ static int dlfb_ops_mmap(struct fb_info *info, struct vm_area_struct *vma)
unsigned long page, pos;
struct dlfb_data *dlfb = info->par;
+ if (info->fbdefio)
+ return fb_deferred_io_mmap(info, vma);
+
if (vma->vm_pgoff > (~0UL >> PAGE_SHIFT))
return -EINVAL;
if (size > info->fix.smem_len)
diff --git a/drivers/video/fbdev/xen-fbfront.c b/drivers/video/fbdev/xen-fbfront.c
index 37e3f226f78ce..91f0a9ceede1a 100644
--- a/drivers/video/fbdev/xen-fbfront.c
+++ b/drivers/video/fbdev/xen-fbfront.c
@@ -338,6 +338,7 @@ static const struct fb_ops xenfb_fb_ops = {
.fb_imageblit = xenfb_imageblit,
.fb_check_var = xenfb_check_var,
.fb_set_par = xenfb_set_par,
+ .fb_mmap = fb_deferred_io_mmap,
};
static irqreturn_t xenfb_event_handler(int rq, void *dev_id)
--
2.53.0
next prev parent reply other threads:[~2026-09-08 1:18 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-03 13:41 FAILED: patch "[PATCH] fbdev: ssd1307fb: defer I2C transfers from damage callbacks" failed to apply to 5.15-stable tree gregkh
2026-09-08 1:18 ` Sasha Levin [this message]
2026-09-08 1:18 ` [PATCH 5.15.y 2/6] fbdev: Don't re-validate info->state in fb_ops implementations Sasha Levin
2026-09-08 1:18 ` [PATCH 5.15.y 3/6] fbdev: Validate info->screen_{base, buffer} " Sasha Levin
2026-09-08 1:18 ` [PATCH 5.15.y 4/6] fbdev: Add initializer macros for struct fb_ops Sasha Levin
2026-09-08 1:18 ` [PATCH 5.15.y 5/6] fbdev/ssd1307fb: Generate deferred I/O ops Sasha Levin
2026-09-08 1:18 ` [PATCH 5.15.y 6/6] fbdev: ssd1307fb: defer I2C transfers from damage callbacks Sasha Levin
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