[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+renesas at 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