Re: [PATCH] fbdev: xilinxfb: request memory region before mapping framebuffer

[Helge Deller]

On 12/15/25 23:53, patdivi...@gmail.com wrote:

From: DiviyamPathak <patdivi...@gmail.com>

The xilinxfb driver maps a physical framebuffer address with ioremap()
without first reserving the memory region. This can conflict with other
drivers accessing the same resource.

Request the memory region with devm_request_mem_region() before mapping
the framebuffer and use managed mappings for proper lifetime handling.

This addresses the fbdev TODO about requesting memory regions and avoids
potential resource conflicts.

Signed-off-by: DiviyamPathak <patdivi...@gmail.com>

Was it tested it on physical hardware?
If not, could someone test?

Helge

---
  drivers/video/fbdev/xilinxfb.c | 30 +++++++++++++++++-------------
  1 file changed, 17 insertions(+), 13 deletions(-)

diff --git a/drivers/video/fbdev/xilinxfb.c b/drivers/video/fbdev/xilinxfb.c
index 0a6e05cd155a..f18437490de8 100644
--- a/drivers/video/fbdev/xilinxfb.c
+++ b/drivers/video/fbdev/xilinxfb.c
@@ -280,19 +280,27 @@ static int xilinxfb_assign(struct platform_device *pdev,
        /* Allocate the framebuffer memory */
        if (pdata->fb_phys) {
                drvdata->fb_phys = pdata->fb_phys;
-               drvdata->fb_virt = ioremap(pdata->fb_phys, fbsize);
+               /* Request the memory region before mapping */
+               if (!devm_request_mem_region(dev, pdata->fb_phys, fbsize,
+                                       DRIVER_NAME)) {
+                       dev_err(dev, "Cannot request framebuffer memory 
region\n");
+                       return -EBUSY;
+               }
+               drvdata->fb_virt = devm_ioremap(dev, pdata->fb_phys, fbsize);
+               if (!drvdata->fb_virt) {
+                       dev_err(dev, "Could not map framebuffer memory\n");
+                       return -ENOMEM;
+               }
        } else {
                drvdata->fb_alloced = 1;
                drvdata->fb_virt = dma_alloc_coherent(dev, PAGE_ALIGN(fbsize),
-                                                     &drvdata->fb_phys,
-                                                     GFP_KERNEL);
-       }
-
-       if (!drvdata->fb_virt) {
-               dev_err(dev, "Could not allocate frame buffer memory\n");
-               return -ENOMEM;
+                                       &drvdata->fb_phys,
+                                       GFP_KERNEL);
+               if (!drvdata->fb_virt) {
+                       dev_err(dev, "Could not allocate frame buffer 
memory\n");
+                       return -ENOMEM;
+               }
        }
-
        /* Clear (turn to black) the framebuffer */
        memset_io((void __iomem *)drvdata->fb_virt, 0, fbsize);

@@ -362,8 +370,6 @@ static int xilinxfb_assign(struct platform_device *pdev,

        if (drvdata->fb_alloced)
                dma_free_coherent(dev, PAGE_ALIGN(fbsize), drvdata->fb_virt,
                                  drvdata->fb_phys);
-       else
-               iounmap(drvdata->fb_virt);

/* Turn off the display */

        xilinx_fb_out32(drvdata, REG_CTRL, 0);
@@ -386,8 +392,6 @@ static void xilinxfb_release(struct device *dev)
        if (drvdata->fb_alloced)
                dma_free_coherent(dev, PAGE_ALIGN(drvdata->info.fix.smem_len),
                                  drvdata->fb_virt, drvdata->fb_phys);
-       else
-               iounmap(drvdata->fb_virt);

/* Turn off the display */

        xilinx_fb_out32(drvdata, REG_CTRL, 0);