[PATCH] drm/sysfb: efidrm: Fix framebuffer mapping error handling

[Chen Ni]

devm_memremap() returns an error pointer on failure, not NULL. Using
!screen_base to check for errors will miss error codes and treat invalid
pointers as valid addresses.

devm_memremap() returns system memory pointers (void *), while
devm_ioremap() returns I/O memory pointers (void __iomem *). The current
code incorrectly passes system memory pointers to
iosys_map_set_vaddr_iomem(), which expects I/O memory.

Fix these issues by:
- Properly checking IS_ERR() for devm_memremap() return values.
- Using iosys_map_set_vaddr_iomem() for I/O memory mappings (WC/UC).
- Using iosys_map_set_vaddr() for system memory mappings (WT/WB).

Fixes: 32ae90c66fb6 ("drm/sysfb: Add efidrm for EFI displays")
Signed-off-by: Chen Ni <nic...@iscas.ac.cn>
---
 drivers/gpu/drm/sysfb/efidrm.c | 42 ++++++++++++++++++++++++----------
 1 file changed, 30 insertions(+), 12 deletions(-)

diff --git a/drivers/gpu/drm/sysfb/efidrm.c b/drivers/gpu/drm/sysfb/efidrm.c
index 1114359a1e62..a1da841a8dd4 100644
--- a/drivers/gpu/drm/sysfb/efidrm.c
+++ b/drivers/gpu/drm/sysfb/efidrm.c
@@ -158,6 +158,7 @@ static struct efidrm_device *efidrm_device_create(struct 
drm_driver *drv,
        struct drm_device *dev;
        struct resource *mem = NULL;
        void __iomem *screen_base = NULL;
+       void *sys_base = NULL;
        struct drm_plane *primary_plane;
        struct drm_crtc *crtc;
        struct drm_encoder *encoder;
@@ -165,6 +166,7 @@ static struct efidrm_device *efidrm_device_create(struct 
drm_driver *drv,
        unsigned long max_width, max_height;
        size_t nformats;
        int ret;
+       bool is_iomem = false;
 
        dpy = dev_get_platdata(&pdev->dev);
        if (!dpy)
@@ -244,21 +246,37 @@ static struct efidrm_device *efidrm_device_create(struct 
drm_driver *drv,
 
        mem_flags = efidrm_get_mem_flags(dev, res->start, vsize);
 
-       if (mem_flags & EFI_MEMORY_WC)
+       if (mem_flags & EFI_MEMORY_WC) {
                screen_base = devm_ioremap_wc(&pdev->dev, mem->start, 
resource_size(mem));
-       else if (mem_flags & EFI_MEMORY_UC)
+               is_iomem = true;
+               if (!screen_base)
+                       return ERR_PTR(-ENOMEM);
+       } else if (mem_flags & EFI_MEMORY_UC) {
                screen_base = devm_ioremap(&pdev->dev, mem->start, 
resource_size(mem));
-       else if (mem_flags & EFI_MEMORY_WT)
-               screen_base = devm_memremap(&pdev->dev, mem->start, 
resource_size(mem),
-                                           MEMREMAP_WT);
-       else if (mem_flags & EFI_MEMORY_WB)
-               screen_base = devm_memremap(&pdev->dev, mem->start, 
resource_size(mem),
-                                           MEMREMAP_WB);
-       else
+               is_iomem = true;
+               if (!screen_base)
+                       return ERR_PTR(-ENOMEM);
+       } else if (mem_flags & EFI_MEMORY_WT) {
+               sys_base = devm_memremap(&pdev->dev, mem->start, 
resource_size(mem),
+                                        MEMREMAP_WT);
+               is_iomem = false;
+               if (IS_ERR(sys_base))
+                       return sys_base;
+       } else if (mem_flags & EFI_MEMORY_WB) {
+               sys_base = devm_memremap(&pdev->dev, mem->start, 
resource_size(mem),
+                                        MEMREMAP_WB);
+               is_iomem = false;
+               if (IS_ERR(sys_base))
+                       return sys_base;
+       } else {
                drm_err(dev, "invalid mem_flags: 0x%llx\n", mem_flags);
-       if (!screen_base)
-               return ERR_PTR(-ENOMEM);
-       iosys_map_set_vaddr_iomem(&sysfb->fb_addr, screen_base);
+               return ERR_PTR(-EINVAL);
+       }
+
+       if (is_iomem)
+               iosys_map_set_vaddr_iomem(&sysfb->fb_addr, screen_base);
+       else
+               iosys_map_set_vaddr(&sysfb->fb_addr, sys_base);
 
        /*
         * Modesetting
-- 
2.25.1