framebuffer: Support nonstandard stride

- Add new (optional) stride field in the fb_ctx_t description, pass it to the FDT
- Calculate framebuffer region size accordingly
- This allows direct mapping of unusual framebuffers on the host

src/devices/framebuffer.c

@@ -36,7 +36,7 @@ static rvvm_mmio_type_t fb_dev_type = {
 PUBLIC void framebuffer_init(rvvm_machine_t* machine, rvvm_addr_t addr, const fb_ctx_t* fb)
 {
     rvvm_mmio_dev_t fb_region = {0};
-    
+
     // Map the framebuffer into physical memory
     fb_region.data = fb->buffer;
     fb_region.addr = addr;
@@ -66,7 +66,7 @@ PUBLIC void framebuffer_init(rvvm_machine_t* machine, rvvm_addr_t addr, const fb
     }
     fdt_node_add_prop_u32(fb_fdt, "width",  fb->width);
     fdt_node_add_prop_u32(fb_fdt, "height", fb->height);
-    fdt_node_add_prop_u32(fb_fdt, "stride", fb->width * rgb_format_bytes(fb->format));
+    fdt_node_add_prop_u32(fb_fdt, "stride", framebuffer_stride(fb));
 
     fdt_node_add_child(rvvm_get_fdt_soc(machine), fb_fdt);
 #endif

src/devices/framebuffer.h

@@ -33,6 +33,7 @@ typedef struct {
     void*     buffer;
     uint32_t  width;
     uint32_t  height;
+    uint32_t  stride;
     rgb_fmt_t format;
 } fb_ctx_t;
 
@@ -64,9 +65,14 @@ static inline size_t rgb_format_from_bpp(size_t bpp)
     return RGB_FMT_INVALID;
 }
 
+static inline uint32_t framebuffer_stride(const fb_ctx_t* fb)
+{
+    return fb->stride ? fb->stride : fb->width * rgb_format_bytes(fb->format);
+}
+
 static inline size_t framebuffer_size(const fb_ctx_t* fb)
 {
-    return rgb_format_bytes(fb->format) * fb->width * fb->height;
+    return framebuffer_stride(fb) * fb->height;
 }
 
 // Attach initialized framebuffer context to the machine