From 933d309fe7987b3cc08bea94f380669f20c1ea4b Mon Sep 17 00:00:00 2001
From: xinbingnan <xinbingnan@xiaomi.com>
Date: Sun, 27 Apr 2025 22:30:21 +0800
Subject: [PATCH] examples/fb: support for complete non-/consecutive fbdev mmap
 processing

Enhance fbdev mmap handling to support both consecutive and
non-consecutive
memory layouts. The implementation now correctly calculates memory
offsets
and performs mmap operations for the second framebuffer plane based on
the
physical memory addresses returned by the driver.

Key changes:
- Retrieve physical memory addresses for both display planes
- Detect consecutive vs non-consecutive memory layouts
- Calculate proper offset for mmap operations
- Adjust framebuffer length based on memory layout
- Improve error handling and resource cleanup

Signed-off-by: xinbingnan <xinbingnan@xiaomi.com>
---
 examples/fb/fb_main.c | 79 +++++++++++++++++++++++++++----------------
 1 file changed, 50 insertions(+), 29 deletions(-)

diff --git a/examples/fb/fb_main.c b/examples/fb/fb_main.c
index bd7d457e1c7..7220c1fb641 100644
--- a/examples/fb/fb_main.c
+++ b/examples/fb/fb_main.c
@@ -195,30 +195,41 @@ static int fbdev_get_pinfo(int fd, FAR struct fb_planeinfo_s *pinfo)
 
 static int fb_init_mem2(FAR struct fb_state_s *state)
 {
-  int ret;
-  uintptr_t buf_offset;
   struct fb_planeinfo_s pinfo;
-  FAR void *fbmem;
+  FAR void * phy_mem1;
+  FAR void * phy_mem2;
+  bool is_consecutive;
+  uintptr_t offset;
+  uint32_t fblen;
+  int ret;
+
+  /* Get display[0] planeinfo */
 
   memset(&pinfo, 0, sizeof(pinfo));
-  pinfo.display = state->pinfo.display + 1;
+  pinfo.display = state->pinfo.display;
 
   if ((ret = fbdev_get_pinfo(state->fd, &pinfo)) < 0)
     {
-      return EXIT_FAILURE;
+      return ret;
     }
 
-  fbmem = mmap(NULL, pinfo.fblen, PROT_READ | PROT_WRITE,
-               MAP_SHARED | MAP_FILE, state->fd, 0);
+  phy_mem1 = pinfo.fbmem;
 
-  if (fbmem == MAP_FAILED)
+  /* Get display[1] planeinfo */
+
+  memset(&pinfo, 0, sizeof(pinfo));
+  pinfo.display = state->pinfo.display + 1;
+
+  if ((ret = fbdev_get_pinfo(state->fd, &pinfo)) < 0)
     {
-      int errcode = errno;
-      fprintf(stderr, "ERROR: ioctl(FBIOGET_PLANEINFO) failed: %d\n",
-              errcode);
-      return EXIT_FAILURE;
+      return ret;
     }
 
+  phy_mem2 = pinfo.fbmem;
+
+  offset = (uintptr_t)phy_mem2 - (uintptr_t)phy_mem1;
+  is_consecutive = offset == 0;
+
   /* Check bpp */
 
   if (pinfo.bpp != state->pinfo.bpp)
@@ -231,37 +242,44 @@ static int fb_init_mem2(FAR struct fb_state_s *state)
    * It needs to be divisible by pinfo.stride
    */
 
-  buf_offset = fbmem - state->fbmem;
-
-  if ((buf_offset % state->pinfo.stride) != 0)
+  if ((offset % state->pinfo.stride) != 0)
     {
       fprintf(stderr, "ERROR: It is detected that buf_offset(%" PRIuPTR ") "
               "and stride(%d) are not divisible, please ensure "
               "that the driver handles the address offset by itself.\n",
-              buf_offset, state->pinfo.stride);
+              offset, state->pinfo.stride);
     }
 
   /* Calculate the address and yoffset of fbmem2 */
 
-  if (buf_offset == 0)
+  if (is_consecutive)
     {
-      /* Use consecutive fbmem2. */
-
       state->mem2_yoffset = state->vinfo.yres;
-      state->fbmem2 = fbmem + state->mem2_yoffset * pinfo.stride;
-      printf("Use consecutive fbmem2 = %p, yoffset = %" PRIu32"\n",
-             state->fbmem2, state->mem2_yoffset);
+      offset = state->vinfo.yres * pinfo.stride;
     }
   else
     {
-      /* Use non-consecutive fbmem2. */
+      state->mem2_yoffset = offset / state->pinfo.stride;
+    }
+
+  fblen = is_consecutive ? pinfo.fblen / 2 : pinfo.fblen;
+  void * mem2 = mmap(NULL, fblen,
+                    PROT_READ | PROT_WRITE,
+                    MAP_SHARED | MAP_FILE,
+                    state->fd, offset);
 
-      state->mem2_yoffset = buf_offset / state->pinfo.stride;
-      state->fbmem2 = fbmem;
-      printf("Use non-consecutive fbmem2 = %p, yoffset = %" PRIu32"\n",
-             state->fbmem2, state->mem2_yoffset);
+  if (mem2 == MAP_FAILED)
+    {
+      fprintf(stderr, "ERROR: mmap failed: %d, offset: %" PRIuPTR,
+            errno, offset);
+      return -errno;
     }
 
+  state->fbmem2 = mem2;
+  fprintf(stderr, "Use of %sconsecutive mem2 = %p, yoffset = %" PRIu32,
+          is_consecutive ? "" : "non-", state->fbmem2,
+          state->mem2_yoffset);
+
   return 0;
 }
 
@@ -648,7 +666,9 @@ int main(int argc, FAR char *argv[])
     {
       if ((ret = fb_init_mem2(&state)) < 0)
         {
-          goto out;
+          munmap(state.fbmem, state.pinfo.fblen);
+          close(state.fd);
+          return ret;
         }
     }
 
@@ -689,8 +709,9 @@ int main(int argc, FAR char *argv[])
 
   printf("Test finished\n");
   ret = EXIT_SUCCESS;
-out:
+
   munmap(state.fbmem, state.pinfo.fblen);
+  munmap(state.fbmem2, state.pinfo.fblen);
   close(state.fd);
   return ret;
 }