Re: [PATCH 1/2] fbdev: fbmem: add a helper to determine if an aperture is used by a fw fb

[Thomas Zimmermann]

Hi

Am 27.12.21 um 19:25 schrieb Alex Deucher:

Add a function for drivers to check if the a firmware initialized
fb is corresponds to their aperture.  This allows drivers to check if the
device corresponds to what the firmware set up as the display device.

Best regards
Thomas

If simpledrm is in use, it will register via DRM aperture helpers. You probably need a similar function in drm_aperture.c to handle this.

Bug: https://bugzilla.kernel.org/show_bug.cgi?id=215203
Bug: https://gitlab.freedesktop.org/drm/amd/-/issues/1840
Signed-off-by: Alex Deucher <alexander.deuc...@amd.com>
---
  drivers/video/fbdev/core/fbmem.c | 47 ++++++++++++++++++++++++++++++++
  include/linux/fb.h               |  1 +
  2 files changed, 48 insertions(+)

diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c
index 826175ad88a2..0fa7ede94fa6 100644
--- a/drivers/video/fbdev/core/fbmem.c
+++ b/drivers/video/fbdev/core/fbmem.c
@@ -1762,6 +1762,53 @@ int remove_conflicting_framebuffers(struct 
apertures_struct *a,
  }
  EXPORT_SYMBOL(remove_conflicting_framebuffers);

+ * is_firmware_framebuffer - detect if firmware-configured framebuffer matches
+ * @a: memory range, users of which are to be checked
+ *
+ * This function checks framebuffer devices (initialized by 
firmware/bootloader)
+ * which use memory range described by @a. If @a matchesm the function returns
+ * true, otherwise false.
+ */
+bool is_firmware_framebuffer(struct apertures_struct *a)
+{
+       bool do_free = false;
+       bool found = false;
+       int i;
+
+       if (!a) {
+               a = alloc_apertures(1);
+               if (!a)
+                       return false;
+
+               a->ranges[0].base = 0;
+               a->ranges[0].size = ~0;
+               do_free = true;
+       }
+
+       mutex_lock(&registration_lock);
+       /* check all firmware fbs and kick off if the base addr overlaps */
+       for_each_registered_fb(i) {
+               struct apertures_struct *gen_aper;
+
+               if (!(registered_fb[i]->flags & FBINFO_MISC_FIRMWARE))
+                       continue;
+
+               gen_aper = registered_fb[i]->apertures;
+               if (fb_do_apertures_overlap(gen_aper, a)) {
+                       found = true;
+                       break;
+               }
+       }
+       mutex_unlock(&registration_lock);
+
+       if (do_free)
+               kfree(a);
+
+       return found;
+}
+EXPORT_SYMBOL(is_firmware_framebuffer);
+
  /**
   * remove_conflicting_pci_framebuffers - remove firmware-configured 
framebuffers for PCI devices
   * @pdev: PCI device
diff --git a/include/linux/fb.h b/include/linux/fb.h
index 6f3db99ab990..3da95842b207 100644
--- a/include/linux/fb.h
+++ b/include/linux/fb.h
@@ -610,6 +610,7 @@ extern int remove_conflicting_pci_framebuffers(struct 
pci_dev *pdev,
                                               const char *name);
  extern int remove_conflicting_framebuffers(struct apertures_struct *a,
                                           const char *name, bool primary);
+extern bool is_firmware_framebuffer(struct apertures_struct *a);
  extern int fb_prepare_logo(struct fb_info *fb_info, int rotate);
  extern int fb_show_logo(struct fb_info *fb_info, int rotate);
  extern char* fb_get_buffer_offset(struct fb_info *info, struct fb_pixmap 
*buf, u32 size);

+/**

--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Ivo Totev

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