On 06/28/2013 04:11 AM, David Herrmann wrote:
Hi
On Wed, Jun 26, 2013 at 10:49 PM, Stephen Warren swarren@wwwdotorg.org wrote:
On 06/24/2013 04:27 PM, David Herrmann wrote:
The current situation regarding boot-framebuffers (VGA, VESA/VBE, EFI) on x86 causes troubles when loading multiple fbdev drivers. The global "struct screen_info" does not provide any state-tracking about which drivers use the FBs. request_mem_region() theoretically works, but unfortunately vesafb/efifb ignore it due to quirks for broken boards.
Avoid this by creating a "platform-framebuffer" device with a pointer to the "struct screen_info" as platform-data. Drivers can now create platform-drivers and the driver-core will refuse multiple drivers being active simultaneously.
We keep the screen_info available for backwards-compatibility. Drivers can be converted in follow-up patches.
Apart from "platform-framebuffer" devices, this also introduces a compatibility option for "simple-framebuffer" drivers which recently got introduced for OF based systems. If CONFIG_X86_SYSFB is selected, we try to match the screen_info against a simple-framebuffer supported format. If we succeed, we create a "simple-framebuffer" device instead of a platform-framebuffer.
...
diff --git a/arch/x86/kernel/sysfb.c b/arch/x86/kernel/sysfb.c
...
+#else /* CONFIG_X86_SYSFB */
+static bool parse_mode(const struct screen_info *si,
struct simplefb_platform_data *mode)+{
return false;+}
+static int create_simplefb(const struct screen_info *si,
const struct simplefb_platform_data *mode)+{
return -EINVAL;+}
+#endif /* CONFIG_X86_SYSFB */
Following on from my ifdef comment above, I believe those versions of those functions will always cause add_sysfb() to return -ENODEV, so you may as well provide a static inline for add_sysfb() instead.
No. add_sysfb() is supposed to always succeed. However, if parse_mode/create_simplefb fail, it creates a "platform-framebuffer" as fallback. I don't see any way to avoid these ifdefs. Considering the explanation above, could you elaborate how you think this should work?
Ah, I wasn't getting the fallback mechanism; that if creating a simplefb wasn't possible or didn't succeed, a platformfb device would be created instead.
Perhaps the following might be slightly clearer; there are certainly fewer nesting levels:
static __init int add_sysfb(void) { const struct screen_info *si = &screen_info; struct simplefb_platform_data mode; struct platform_device *pd; bool compatible = false; int ret;
compatible = parse_mode(si, &mode); if (compatible) { ret = create_simplefb(si, &mode); if (!ret) return 0; }
pd = platform_device_register_resndata(NULL, "platform-framebuffer", 0, NULL, 0, si, sizeof(*si)); ret = IS_ERR(pd) ? PTR_ERR(pd) : 0;
return ret; }