Re: [PATCH v2 5/7] drm: Implement struct vga_switcheroo_client_ops.pre_switch

[Thomas Zimmermann]

Am 09.07.26 um 11:36 schrieb sashiko-...@kernel.org:

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) 
to consider:
- [Low] `vga_switcheroo_client_fb_set()` and the `fb_info` field in `struct 
vga_switcheroo_client` are orphaned and remain as dead code.

Patch 7 cleans them up.

--

--- Patch [5]: [PATCH v2 5/7] drm: Implement struct 
vga_switcheroo_client_ops.pre_switch ---
commit d5ba75db20f40c6dde86b90da7c25acad6f23b57
Author: Thomas Zimmermann <tzimmerm...@suse.de>

drm: Implement struct vga_switcheroo_client_ops.pre_switch

This commit implements the pre_switch callback for vga_switcheroo in amdgpu,
i915, nouveau, and radeon drivers. It pushes fbcon updates from vga_switcheroo
into DRM's fbdev emulation and removes calls to vga_switcheroo_client_fb_set()
from fbcon to prevent deadlocks.

diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c
index 9f5c4c101581d..974c7dcf52514 100644
--- a/drivers/video/fbdev/core/fbcon.c
+++ b/drivers/video/fbdev/core/fbcon.c

[ ... ]

@@ -2987,10 +2983,6 @@ static int do_fb_registered(struct fb_info *info)
                }
        }

- /* Set the fb info for vga_switcheroo clients. Does nothing otherwise. */

-       if (info->device && dev_is_pci(info->device))
-               vga_switcheroo_client_fb_set(to_pci_dev(info->device), info);
-

[Severity: Low]
With the removal of these calls from fbcon, are there any remaining users of
vga_switcheroo_client_fb_set()?

It looks like the exported function in drivers/gpu/vga/vga_switcheroo.c is
now completely unused:

void vga_switcheroo_client_fb_set(struct pci_dev *pdev,
                                 struct fb_info *info)
{
        struct vga_switcheroo_client *client;

        mutex_lock(&vgasr_mutex);
        client = find_client_from_pci(&vgasr_priv.clients, pdev);
        if (client)
                client->fb_info = info;
        mutex_unlock(&vgasr_mutex);
}
EXPORT_SYMBOL(vga_switcheroo_client_fb_set);

Because client->fb_info is never populated, does this also leave dead code
in vga_switchto_stage2() where it checks for the fallback?

#if defined(CONFIG_FB)
        else if (new_client->fb_info)
                fb_switch_outputs(new_client->fb_info);
#endif

Would it make sense to remove the orphaned vga_switcheroo_client_fb_set()
function, the fb_info field in struct vga_switcheroo_client, and the
unreachable fallback block to complete the cleanup?

        return ret;
  }

--
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstr. 146, 90461 Nürnberg, Germany, www.suse.com
GF: Jochen Jaser, Andrew McDonald, (HRB 36809, AG Nürnberg)