Re: [PATCH v2 7/7] drm/panic: Add support for drawing a monochrome graphical logo

[Jocelyn Falempe]

On 13/06/2024 21:18, Geert Uytterhoeven wrote:
Re-use the existing support for boot-up logos to draw a monochrome
graphical logo in the DRM panic handler.  When no suitable graphical
logo is available, the code falls back to the ASCII art penguin logo.

Note that all graphical boot-up logos are freed during late kernel
initialization, hence a copy must be made for later use.

Signed-off-by: Geert Uytterhoeven <geert+rene...@glider.be>
---
v2:
   - Rebased,
   - Inline trivial draw_logo_mono().
---
  drivers/gpu/drm/drm_panic.c | 65 +++++++++++++++++++++++++++++++++----
  drivers/video/logo/Kconfig  |  2 ++
  2 files changed, 60 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/drm_panic.c b/drivers/gpu/drm/drm_panic.c
index f7e22b69bb25d3be..af30f243b2802ad7 100644
--- a/drivers/gpu/drm/drm_panic.c
+++ b/drivers/gpu/drm/drm_panic.c
@@ -7,11 +7,15 @@
   */
  
  #include <linux/font.h>
+#include <linux/init.h>
  #include <linux/iosys-map.h>
  #include <linux/kdebug.h>
  #include <linux/kmsg_dump.h>
+#include <linux/linux_logo.h>
  #include <linux/list.h>
+#include <linux/math.h>
  #include <linux/module.h>
+#include <linux/overflow.h>
  #include <linux/printk.h>
  #include <linux/types.h>
  
@@ -88,6 +92,42 @@ static const struct drm_panic_line logo_ascii[] = {
        PANIC_LINE(" \\___)=(___/"),
  };
  
+#ifdef CONFIG_LOGO
+static const struct linux_logo *logo_mono;
+
+static int drm_panic_setup_logo(void)
+{
+       const struct linux_logo *logo = fb_find_logo(1);
+       const unsigned char *logo_data;
+       struct linux_logo *logo_dup;
+
+       if (!logo || logo->type != LINUX_LOGO_MONO)
+               return 0;
+
+       /* The logo is __init, so we must make a copy for later use */
+       logo_data = kmemdup(logo->data,
+                           size_mul(DIV_ROUND_UP(logo->width, BITS_PER_BYTE), 
logo->height),
+                           GFP_KERNEL);
+       if (!logo_data)
+               return -ENOMEM;
+
+       logo_dup = kmemdup(logo, sizeof(*logo), GFP_KERNEL);
+       if (!logo_dup) {
+               kfree(logo_data);
+               return -ENOMEM;
+       }
+
+       logo_dup->data = logo_data;
+       logo_mono = logo_dup;
+
+       return 0;
+}
+
+device_initcall(drm_panic_setup_logo);
+#else
+#define logo_mono      ((const struct linux_logo *)NULL)
+#endif

I didn't notice that the first time, but the core drm can be built as a 
module.
That means this will leak memory each time the module is removed.

But to solve the circular dependency between drm_kms_helper and 
drm_panic, one solution is to depends on drm core to be built-in.
In this case there won't be a leak.
So depending on how we solve the circular dependency, it can be acceptable.

--

Jocelyn