Build failure: implicit declaration of drm_clflush_virt_range on architecture other than x86

This occurs because the header file <drm/drm_cache.h> is currently included conditionally, restricted only to x86 architectures:

evdi/module/evdi_painter.c

Lines 23 to 25 in 750044c

    
           #if defined(CONFIG_X86) 
        
           #include <drm/drm_cache.h> 
        
           #endif

However, the function copy_primary_pixels_on_xe utilizes drm_clflush_virt_range and drm_memcpy_from_wc (defined in that header), but the function definition itself is not guarded by the same architecture checks:

evdi/module/evdi_painter.c

Lines 178 to 209 in 750044c

    
           #if KERNEL_VERSION(5, 18, 0) <= LINUX_VERSION_CODE || defined(EL8) || defined(EL9) 
        
           static int copy_primary_pixels_on_xe(struct evdi_framebuffer *efb, 
        
           			       char __user *buffer, 
        
           			       int buf_byte_stride, 
        
           			       int const max_x, 
        
           			       int const max_y) 
        
           { 
        
           	int y; 
        
           	struct drm_framebuffer *fb = &efb->base; 
        
           	const int byte_span = max_x * 4; 
        
           	struct iosys_map dst_mapping = IOSYS_MAP_INIT_VADDR(vmalloc(max_x * 4)); 
        
           	for (y = 0; y < max_y; ++y) { 
        
           		const int src_offset = fb->offsets[0] + fb->pitches[0] * y; 
        
           		struct iosys_map src_mapping = IOSYS_MAP_INIT_VADDR((char *)efb->obj->vmapping + src_offset); 
        
           		const int dst_offset = buf_byte_stride * y; 
        
           		char __user *dst = buffer + dst_offset; 
        
           		drm_clflush_virt_range(src_mapping.vaddr, byte_span); 
        
           		drm_memcpy_from_wc(&dst_mapping, &src_mapping, byte_span); 
        
           		if (copy_to_user(dst, dst_mapping.vaddr, byte_span)) 
        
           			return -EFAULT; 
        
           		src_mapping.vaddr += fb->pitches[0]; 
        
           		dst += buf_byte_stride; 
        
           	} 
        
           	vfree(dst_mapping.vaddr); 
        
           	return 0; 
        
           } 
        
           #endif

This mismatch causes the build to fail when targeting non-x86 architectures (such as AArch64), as the compiler cannot find the definitions for the DRM cache functions.

> /build/source/module/evdi_painter.c: In function 'copy_primary_pixels_on_xe':
2026-02-09T14:17:28.3342031Z evdi> /build/source/module/evdi_painter.c:196:17: error: implicit declaration of function 'drm_clflush_virt_range' [-Wimplicit-function-declaration]
2026-02-09T14:17:28.3342707Z evdi>   196 |                 drm_clflush_virt_range(src_mapping.vaddr, byte_span);
2026-02-09T14:17:28.3343032Z evdi>       |                 ^~~~~~~~~~~~~~~~~~~~~~

Ref: NixOS/nixpkgs#488694

This occurs because the header file <drm/drm_cache.h> is currently included conditionally, restricted only to x86 architectures:

I am on Asahi Linux (aarch64), and I can confirm that making the include unconditional gets it to compile for me:

diff --git a/module/evdi_painter.c b/module/evdi_painter.c
index 4a1d2d5..46e11d8 100644
--- a/module/evdi_painter.c
+++ b/module/evdi_painter.c
@@ -20,9 +20,7 @@
 #include <drm/drmP.h>
 #endif
 #include <drm/drm_edid.h>
-#if defined(CONFIG_X86)
 #include <drm/drm_cache.h>
-#endif
 #include "evdi_drm.h"
 #include "evdi_drm_drv.h"
 #include "evdi_cursor.h"

d I can confirm that making the include unconditional gets it to compile for me

Good catch. Can you please submit PR?

Unconditionally include <drm/drm_cache.h>.

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Build failure: implicit declaration of `drm_clflush_virt_range` on architecture other than x86 #555

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	#if KERNEL_VERSION(5, 18, 0) <= LINUX_VERSION_CODE \|\| defined(EL8) \|\| defined(EL9)
	static int copy_primary_pixels_on_xe(struct evdi_framebuffer *efb,
	char __user *buffer,
	int buf_byte_stride,
	int const max_x,
	int const max_y)
	{
	int y;
	struct drm_framebuffer *fb = &efb->base;
	const int byte_span = max_x * 4;
	struct iosys_map dst_mapping = IOSYS_MAP_INIT_VADDR(vmalloc(max_x * 4));

	for (y = 0; y < max_y; ++y) {
	const int src_offset = fb->offsets[0] + fb->pitches[0] * y;
	struct iosys_map src_mapping = IOSYS_MAP_INIT_VADDR((char *)efb->obj->vmapping + src_offset);
	const int dst_offset = buf_byte_stride * y;
	char __user *dst = buffer + dst_offset;

	drm_clflush_virt_range(src_mapping.vaddr, byte_span);
	drm_memcpy_from_wc(&dst_mapping, &src_mapping, byte_span);
	if (copy_to_user(dst, dst_mapping.vaddr, byte_span))
	return -EFAULT;

	src_mapping.vaddr += fb->pitches[0];
	dst += buf_byte_stride;
	}

	vfree(dst_mapping.vaddr);
	return 0;

	}
	#endif

Build failure: implicit declaration of drm_clflush_virt_range on architecture other than x86 #555

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zrhoffman commented on Feb 16, 2026

synaptics-lspintzyk commented on Feb 16, 2026

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Build failure: implicit declaration of `drm_clflush_virt_range` on architecture other than x86 #555