From: Thomas Zimmermann <tzimmermann@suse.de>
To: Arnd Bergmann <arnd@arndb.de>, Helge Deller <deller@gmx.de>,
Daniel Vetter <daniel@ffwll.ch>, Dave Airlie <airlied@gmail.com>
Cc: linux-hyperv@vger.kernel.org, linux-efi@vger.kernel.org,
linux-ia64@vger.kernel.org, linux-sh@vger.kernel.org,
Peter Zijlstra <peterz@infradead.org>,
Dave Hansen <dave.hansen@linux.intel.com>,
linux-fbdev@vger.kernel.org, dri-devel@lists.freedesktop.org,
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Borislav Petkov <bp@alien8.de>,
loongarch@lists.linux.dev, Thomas Gleixner <tglx@linutronix.de>,
linux-arm-kernel@lists.infradead.org, x86@kernel.org,
linux-kernel@vger.kernel.org,
Juerg Haefliger <juerg.haefliger@canonical.com>,
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Andrew Morton <akpm@linux-foundation.org>,
linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH 07/12] arch/x86: Declare edid_info in <asm/screen_info.h>
Date: Wed, 5 Jul 2023 10:18:18 +0200 [thread overview]
Message-ID: <150c0fa2-bff2-0644-d6e5-c4dab7f79048@suse.de> (raw)
In-Reply-To: <dd5aa01e-afad-48d2-bf4c-4a58b74f1644@app.fastmail.com>
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Hi Arnd
Am 30.06.23 um 13:53 schrieb Arnd Bergmann:
> On Fri, Jun 30, 2023, at 09:46, Thomas Zimmermann wrote:
>> Am 29.06.23 um 15:21 schrieb Arnd Bergmann:
>>> On Thu, Jun 29, 2023, at 15:01, Thomas Zimmermann wrote:
>>>> Am 29.06.23 um 14:35 schrieb Arnd Bergmann:
>>>>> On Thu, Jun 29, 2023, at 13:45, Thomas Zimmermann wrote:
>>
>>>>
>>>> FIRMWARE_EDID is a user-selectable feature, while ARCH_HAS_EDID_INFO
>>>> announces an architecture feature. They do different things.
>>>
>>> I still have trouble seeing the difference.
>>
>> The idea here is that ARCH_HAS_ signals the architecture's support for
>> the feature. Drivers set 'depends on' in their Kconfig.
>>
>> Another Kconfig token, VIDEO_SCREEN_INFO or FIRMWARE_EDID, would then
>> actually enable the feature. Drivers select VIDEO_SCREEN_INFO or
>> FIRMWARE_EDID and the architectures contains code like
>
> Fair enough. In that case, I guess FIRMWARE_EDID will just depend on
> ARCH_HAS_EDID_INFO, or possibly "depends on FIRMWARE_EDID || EFI"
> after it starts calling into an EFI specific function, right?
>
>> #ifdef VIDEO_SCREEN_INFO
>> struct screen_info screen_info = {
>> /* set values here */
>> }
>> #endif
>>
>> This allows us to disable code that requires screen_info/edid_info, but
>> also disable screen_info/edid_info unless such code has been enabled in
>> the kernel config.
>>
>> Some architectures currently mimic this by guarding screen_info with
>> ifdef CONFIG_VT or similar. I'd like to make this more flexible. The
>> cost of a few more internal Kconfig tokens seems negligible.
>
> I definitely get it for the screen_info, which needs the complexity.
> For ARCHARCH_HAS_EDID_INFO I would hope that it's never selected by
> anything other than x86, so I would still go with just a dependency
> on x86 for simplicity, but I don't mind having the extra symbol if that
> keeps it more consistent with how the screen_info is handled.
Well, I'd like to add edid_info to platforms with EFI. What would be
arm/arm64 and loongarch, I guess. See below for the future plans.
>
>>> I suppose you could use FIRMWARE_EDID on EFI or OF systems without
>>> the need for a global edid_info structure, but that would not
>>> share any code with the current fb_firmware_edid() function.
>>
>> The current code is build on top of screen_info and edid_info. I'd
>> preferably not replace that, if possible.
>
> One way I could imagine this looking in the end would be
> something like
>
> struct screen_info *fb_screen_info(struct device *dev)
> {
> struct screen_info *si = NULL;
>
> if (IS_ENABLED(CONFIG_EFI))
> si = efi_get_screen_info(dev);
>
> if (IS_ENABLED(CONFIG_ARCH_HAS_SCREEN_INFO) && !si)
> si = screen_info;
>
> return si;
> }
>
> corresponding to fb_firmware_edid(). With this, any driver
> that wants to access screen_info would call this function
> instead of using the global pointer, plus either NULL pointer
> check or a CONFIG_ARCH_HAS_SCREEN_INFO dependency.
>
> This way we could completely eliminate the global screen_info
> on arm64, riscv, and loongarch but still use the efi and
> hyperv framebuffer/drm drivers.
If possible, I'd like to remove global screen_info and edid_info
entirely from fbdev and the various consoles.
We currently use screen_info to set up the generic framebuffer device in
drivers/firmware/sysfb.c. I'd like to use edid_info here as well, so
that the generic graphics drivers can get EDID information.
For the few fbdev drivers and consoles that require the global
screen_info/edid_info, I'd rather provide lookup functions in sysfb
(e.g., sysfb_get_screen_info(), sysfb_get_edid_info()). The global
screen_info/edid_info state would then become an internal artifact of
the sysfb code.
Hopefully that explains some of the decisions made in this patchset.
Best regards
Thomas
>
> Arnd
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nuernberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
HRB 36809 (AG Nuernberg)
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next prev parent reply other threads:[~2023-07-05 8:18 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-29 11:45 [PATCH 00/12] arch,fbdev: Move screen_info into arch/ Thomas Zimmermann
2023-06-29 11:45 ` [PATCH 01/12] efi: Do not include <linux/screen_info.h> from EFI header Thomas Zimmermann
2023-07-04 16:23 ` Javier Martinez Canillas
2023-07-05 1:40 ` [01/12] " Sui Jingfeng
2023-07-05 8:00 ` Thomas Zimmermann
2023-06-29 11:45 ` [PATCH 02/12] fbdev/sm712fb: Do not include <linux/screen_info.h> Thomas Zimmermann
2023-07-04 16:25 ` Javier Martinez Canillas
2023-06-29 11:45 ` [PATCH 03/12] sysfb: Do not include <linux/screen_info.h> from sysfb header Thomas Zimmermann
2023-07-04 16:26 ` Javier Martinez Canillas
2023-07-05 1:41 ` [03/12] " Sui Jingfeng
2023-06-29 11:45 ` [PATCH 04/12] staging/sm750fb: Do not include <linux/screen_info.h> Thomas Zimmermann
2023-07-04 16:27 ` Javier Martinez Canillas
2023-06-29 11:45 ` [PATCH 05/12] arch: Remove trailing whitespaces Thomas Zimmermann
2023-07-04 16:27 ` Javier Martinez Canillas
2023-07-05 1:25 ` [05/12] " Sui Jingfeng
2023-06-29 11:45 ` [PATCH 06/12] arch: Declare screen_info in <asm/screen_info.h> Thomas Zimmermann
2023-06-29 12:55 ` WANG Xuerui
2023-06-29 13:03 ` Arnd Bergmann
2023-06-29 13:18 ` Thomas Zimmermann
2023-07-05 1:21 ` [06/12] " Sui Jingfeng
2023-07-05 8:02 ` Thomas Zimmermann
2023-08-18 14:04 ` suijingfeng
2023-08-18 14:18 ` suijingfeng
2023-06-29 11:45 ` [PATCH 07/12] arch/x86: Declare edid_info " Thomas Zimmermann
2023-06-29 12:35 ` Arnd Bergmann
2023-06-29 13:01 ` Thomas Zimmermann
2023-06-29 13:21 ` Arnd Bergmann
2023-06-30 7:46 ` Thomas Zimmermann
2023-06-30 11:53 ` Arnd Bergmann
2023-07-05 8:18 ` Thomas Zimmermann [this message]
2023-07-18 14:47 ` Arnd Bergmann
2023-06-29 11:45 ` [PATCH 08/12] drivers/firmware: Remove trailing whitespaces Thomas Zimmermann
2023-07-05 1:26 ` [08/12] " Sui Jingfeng
2023-07-05 7:46 ` [PATCH 08/12] " Javier Martinez Canillas
2023-06-29 11:45 ` [PATCH 09/12] drivers: Add dependencies on CONFIG_ARCH_HAS_SCREEN_INFO Thomas Zimmermann
2023-06-29 11:45 ` [PATCH 10/12] fbdev/core: Use fb_is_primary_device() in fb_firmware_edid() Thomas Zimmermann
2023-07-05 8:02 ` Javier Martinez Canillas
2023-06-29 11:45 ` [PATCH 11/12] fbdev/core: Protect edid_info with CONFIG_ARCH_HAS_EDID_INFO Thomas Zimmermann
2023-07-05 1:43 ` [11/12] " Sui Jingfeng
2023-06-29 11:45 ` [PATCH 12/12] fbdev/core: Define empty fb_firmware_edid() in <linux/fb.h> Thomas Zimmermann
2023-06-29 13:31 ` [PATCH 00/12] arch,fbdev: Move screen_info into arch/ Arnd Bergmann
2023-06-29 14:15 ` Thomas Zimmermann
2023-06-29 14:42 ` Arnd Bergmann
2023-06-29 14:29 ` Arnd Bergmann
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