From: Javier Martinez Canillas <javierm@redhat.com>
To: Geert Uytterhoeven <geert@linux-m68k.org>,
Thomas Zimmermann <tzimmermann@suse.de>
Cc: daniel.thompson@linaro.org, lee@kernel.org,
linux-sh@vger.kernel.org, jingoohan1@gmail.com, deller@gmx.de,
linux-staging@lists.linux.dev, linux-fbdev@vger.kernel.org,
dri-devel@lists.freedesktop.org, linux-omap@vger.kernel.org,
sam@ravnborg.org
Subject: Re: [PATCH 30/30] fbdev: Make support for userspace interfaces configurable
Date: Thu, 08 Jun 2023 01:07:47 +0200 [thread overview]
Message-ID: <873532eurg.fsf@minerva.mail-host-address-is-not-set> (raw)
In-Reply-To: <CAMuHMdWBUKTgfCD9VLDFh_Tm1J-NJQHpxODs-TuYM7V-dtmGjA@mail.gmail.com>
Geert Uytterhoeven <geert@linux-m68k.org> writes:
Hello Geert and Thomas,
> Hi Thomas,
>
> On Wed, Jun 7, 2023 at 5:15 PM Thomas Zimmermann <tzimmermann@suse.de> wrote:
>> Am 07.06.23 um 10:48 schrieb Geert Uytterhoeven:
>> > On Mon, Jun 5, 2023 at 4:48 PM Thomas Zimmermann <tzimmermann@suse.de> wrote:
>> >> --- a/drivers/video/fbdev/Kconfig
>> >> +++ b/drivers/video/fbdev/Kconfig
>> >> @@ -57,6 +57,15 @@ config FIRMWARE_EDID
>> >> combination with certain motherboards and monitors are known to
>> >> suffer from this problem.
>> >>
>> >> +config FB_DEVICE
>> >> + bool "Provide legacy /dev/fb* device"
>> >
>> > Perhaps "default y if !DRM", although that does not help for a
>> > mixed drm/fbdev kernel build?
>>
>> We could simply set it to "default y". But OTOH is it worth making it a
>> default? Distributions will set it to the value they need/want. The very
>> few people that build their own kernels to get certain fbdev drivers
>> will certainly be able to enable the option by hand as well.
>
> Defaulting to "n" (the default) means causing regressions when these
> few people use an existing defconfig.
>
Having "dfault y if !DRM" makes sense to me. I guess is a corner case but
at least it won't silently be disabled for users that only want fbdev as
Geert mentioned.
I wouldn't call it a regression though, because AFAIK the Kconfig options
are not a stable API ?
>> > Or reserve "FB" for real fbdev drivers, and introduce a new FB_CORE,
>> > to be selected by both FB and DRM_FBDEV_EMULATION?
>> > Then FB_DEVICE can depend on FB_CORE, and default to y if FB.
Funny that you mention because it's exactly what I attempted in the past:
https://lore.kernel.org/all/20210827100531.1578604-1-javierm@redhat.com/T/#u
>>
>> That wouldn't work. In Tumbleweed, we still have efifb and vesafb
>> enabled under certain conditions; merely for the kernel console. We'd
>> have to enable CONFIG_FB, which would bring back the device.
>
> "Default y" does not mean that you cannot disable FB_DEVICE, so
> you are not forced to bring back the device?
>
I think we can have both to make the kernel more configurable:
1) Allow to only disable fbdev user-space APIs (/dev/fb?, /proc/fb, etc),
which is what the series is doing with the new FB_DEVICE config symbol.
2) Allow to disable all "native" fbdev drivers and only keep the DRM fbdev
emulation layer. That's what my series attempted to do with the FB_CORE
Kconfig symbol.
I believe that there are use cases for both, for example as Thomas' said
many distros are disabling all the fbdev drivers and their user-space only
requires DRM/KMS, so makes sense to not expose any fbdev uAPI at all.
But may be that other users want the opposite, they have an old user-space
that requires fbdev, but is running on newer hardware that only have a DRM
driver. So they will want DRM fbdev emulation but none fbdev driver at all.
That's why I think that FB_DEVICE and FB_CORE are complementary and we can
support any combination of the two, if you agree there are uses for either.
--
Best regards,
Javier Martinez Canillas
Core Platforms
Red Hat
WARNING: multiple messages have this Message-ID (diff)
From: Javier Martinez Canillas <javierm@redhat.com>
To: Geert Uytterhoeven <geert@linux-m68k.org>,
Thomas Zimmermann <tzimmermann@suse.de>
Cc: daniel.thompson@linaro.org, linux-staging@lists.linux.dev,
linux-sh@vger.kernel.org, jingoohan1@gmail.com, deller@gmx.de,
lee@kernel.org, dri-devel@lists.freedesktop.org,
linux-fbdev@vger.kernel.org, linux-omap@vger.kernel.org,
sam@ravnborg.org
Subject: Re: [PATCH 30/30] fbdev: Make support for userspace interfaces configurable
Date: Thu, 08 Jun 2023 01:07:47 +0200 [thread overview]
Message-ID: <873532eurg.fsf@minerva.mail-host-address-is-not-set> (raw)
In-Reply-To: <CAMuHMdWBUKTgfCD9VLDFh_Tm1J-NJQHpxODs-TuYM7V-dtmGjA@mail.gmail.com>
Geert Uytterhoeven <geert@linux-m68k.org> writes:
Hello Geert and Thomas,
> Hi Thomas,
>
> On Wed, Jun 7, 2023 at 5:15 PM Thomas Zimmermann <tzimmermann@suse.de> wrote:
>> Am 07.06.23 um 10:48 schrieb Geert Uytterhoeven:
>> > On Mon, Jun 5, 2023 at 4:48 PM Thomas Zimmermann <tzimmermann@suse.de> wrote:
>> >> --- a/drivers/video/fbdev/Kconfig
>> >> +++ b/drivers/video/fbdev/Kconfig
>> >> @@ -57,6 +57,15 @@ config FIRMWARE_EDID
>> >> combination with certain motherboards and monitors are known to
>> >> suffer from this problem.
>> >>
>> >> +config FB_DEVICE
>> >> + bool "Provide legacy /dev/fb* device"
>> >
>> > Perhaps "default y if !DRM", although that does not help for a
>> > mixed drm/fbdev kernel build?
>>
>> We could simply set it to "default y". But OTOH is it worth making it a
>> default? Distributions will set it to the value they need/want. The very
>> few people that build their own kernels to get certain fbdev drivers
>> will certainly be able to enable the option by hand as well.
>
> Defaulting to "n" (the default) means causing regressions when these
> few people use an existing defconfig.
>
Having "dfault y if !DRM" makes sense to me. I guess is a corner case but
at least it won't silently be disabled for users that only want fbdev as
Geert mentioned.
I wouldn't call it a regression though, because AFAIK the Kconfig options
are not a stable API ?
>> > Or reserve "FB" for real fbdev drivers, and introduce a new FB_CORE,
>> > to be selected by both FB and DRM_FBDEV_EMULATION?
>> > Then FB_DEVICE can depend on FB_CORE, and default to y if FB.
Funny that you mention because it's exactly what I attempted in the past:
https://lore.kernel.org/all/20210827100531.1578604-1-javierm@redhat.com/T/#u
>>
>> That wouldn't work. In Tumbleweed, we still have efifb and vesafb
>> enabled under certain conditions; merely for the kernel console. We'd
>> have to enable CONFIG_FB, which would bring back the device.
>
> "Default y" does not mean that you cannot disable FB_DEVICE, so
> you are not forced to bring back the device?
>
I think we can have both to make the kernel more configurable:
1) Allow to only disable fbdev user-space APIs (/dev/fb?, /proc/fb, etc),
which is what the series is doing with the new FB_DEVICE config symbol.
2) Allow to disable all "native" fbdev drivers and only keep the DRM fbdev
emulation layer. That's what my series attempted to do with the FB_CORE
Kconfig symbol.
I believe that there are use cases for both, for example as Thomas' said
many distros are disabling all the fbdev drivers and their user-space only
requires DRM/KMS, so makes sense to not expose any fbdev uAPI at all.
But may be that other users want the opposite, they have an old user-space
that requires fbdev, but is running on newer hardware that only have a DRM
driver. So they will want DRM fbdev emulation but none fbdev driver at all.
That's why I think that FB_DEVICE and FB_CORE are complementary and we can
support any combination of the two, if you agree there are uses for either.
--
Best regards,
Javier Martinez Canillas
Core Platforms
Red Hat
next prev parent reply other threads:[~2023-06-07 23:07 UTC|newest]
Thread overview: 190+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-05 14:47 [PATCH 00/30] fbdev: Make userspace interfaces optional Thomas Zimmermann
2023-06-05 14:47 ` Thomas Zimmermann
2023-06-05 14:47 ` [PATCH 01/30] backlight/bd6107: Compare against struct fb_info.device Thomas Zimmermann
2023-06-05 14:47 ` Thomas Zimmermann
2023-06-07 7:30 ` Javier Martinez Canillas
2023-06-07 7:30 ` Javier Martinez Canillas
2023-06-07 7:34 ` Javier Martinez Canillas
2023-06-07 7:34 ` Javier Martinez Canillas
2023-06-05 14:47 ` [PATCH 02/30] backlight/gpio_backlight: " Thomas Zimmermann
2023-06-05 14:47 ` Thomas Zimmermann
2023-06-05 20:19 ` Ruhl, Michael J
2023-06-05 20:23 ` Sam Ravnborg
2023-06-05 20:23 ` Sam Ravnborg
2023-06-05 20:41 ` Ruhl, Michael J
2023-06-05 20:41 ` Ruhl, Michael J
2023-06-06 7:24 ` Thomas Zimmermann
2023-06-06 7:49 ` Dan Carpenter
2023-06-06 7:49 ` Dan Carpenter
2023-06-06 8:05 ` Thomas Zimmermann
2023-06-06 8:05 ` Thomas Zimmermann
2023-06-05 14:47 ` [PATCH 03/30] backlight/lv5207lp: " Thomas Zimmermann
2023-06-05 14:47 ` Thomas Zimmermann
2023-06-07 7:35 ` Javier Martinez Canillas
2023-06-05 14:47 ` [PATCH 04/30] fbdev/atyfb: Reorder backlight and framebuffer init/cleanup Thomas Zimmermann
2023-06-05 14:47 ` Thomas Zimmermann
2023-06-07 7:36 ` Javier Martinez Canillas
2023-06-07 7:36 ` Javier Martinez Canillas
2023-06-05 14:47 ` [PATCH 05/30] fbdev/atyfb: Use hardware device as backlight parent Thomas Zimmermann
2023-06-05 14:47 ` Thomas Zimmermann
2023-06-07 7:41 ` Javier Martinez Canillas
2023-06-07 7:41 ` Javier Martinez Canillas
2023-06-05 14:47 ` [PATCH 06/30] fbdev/aty128fb: Reorder backlight and framebuffer init/cleanup Thomas Zimmermann
2023-06-05 14:47 ` Thomas Zimmermann
2023-06-07 7:42 ` Javier Martinez Canillas
2023-06-07 7:42 ` Javier Martinez Canillas
2023-06-05 14:47 ` [PATCH 07/30] fbdev/aty128fb: Use hardware device as backlight parent Thomas Zimmermann
2023-06-05 14:47 ` Thomas Zimmermann
2023-06-07 7:55 ` Javier Martinez Canillas
2023-06-07 7:55 ` Javier Martinez Canillas
2023-06-05 14:47 ` [PATCH 08/30] fbdev/broadsheetfb: Call device_remove_file() with hardware device Thomas Zimmermann
2023-06-05 14:47 ` Thomas Zimmermann
2023-06-07 7:55 ` Javier Martinez Canillas
2023-06-05 14:47 ` [PATCH 09/30] fbdev/ep93xx-fb: Alloc DMA memory from " Thomas Zimmermann
2023-06-05 14:47 ` Thomas Zimmermann
2023-06-07 8:47 ` Javier Martinez Canillas
2023-06-07 8:47 ` Javier Martinez Canillas
2023-06-05 14:47 ` [PATCH 10/30] fbdev/ep93xx-fb: Output messages with fb_info() and fb_err() Thomas Zimmermann
2023-06-05 14:47 ` Thomas Zimmermann
2023-06-07 8:59 ` Javier Martinez Canillas
2023-06-07 8:59 ` Javier Martinez Canillas
2023-06-05 14:47 ` [PATCH 11/30] fbdev/ep93xx-fb: Do not assign to struct fb_info.dev Thomas Zimmermann
2023-06-05 14:47 ` Thomas Zimmermann
2023-06-06 5:26 ` Dan Carpenter
2023-06-06 5:26 ` Dan Carpenter
2023-06-07 9:00 ` Javier Martinez Canillas
2023-06-07 9:00 ` Javier Martinez Canillas
2023-06-05 14:47 ` [PATCH 12/30] fbdev/mb862xxfb: Output messages with fb_dbg() and fb_err() Thomas Zimmermann
2023-06-05 14:47 ` Thomas Zimmermann
2023-06-07 9:00 ` Javier Martinez Canillas
2023-06-07 9:00 ` Javier Martinez Canillas
2023-06-05 14:47 ` [PATCH 13/30] fbdev/metronomefb: Use hardware device for dev_err() Thomas Zimmermann
2023-06-05 14:47 ` Thomas Zimmermann
2023-06-07 9:01 ` Javier Martinez Canillas
2023-06-07 9:01 ` Javier Martinez Canillas
2023-06-05 14:47 ` [PATCH 14/30] fbdev/nvidiafb: Reorder backlight and framebuffer init/cleanup Thomas Zimmermann
2023-06-05 14:47 ` Thomas Zimmermann
2023-06-07 9:02 ` Javier Martinez Canillas
2023-06-07 9:02 ` Javier Martinez Canillas
2023-06-05 14:47 ` [PATCH 15/30] fbdev/nvidiafb: Use hardware device as backlight parent Thomas Zimmermann
2023-06-05 14:47 ` Thomas Zimmermann
2023-06-07 9:02 ` Javier Martinez Canillas
2023-06-07 9:02 ` Javier Martinez Canillas
2023-06-05 14:47 ` [PATCH 16/30] fbdev/pxa168fb: Do not assign to struct fb_info.dev Thomas Zimmermann
2023-06-05 14:47 ` Thomas Zimmermann
2023-06-07 9:09 ` Javier Martinez Canillas
2023-06-07 9:09 ` Javier Martinez Canillas
2023-06-05 14:47 ` [PATCH 17/30] fbdev/radeonfb: Reorder backlight and framebuffer cleanup Thomas Zimmermann
2023-06-05 14:47 ` Thomas Zimmermann
2023-06-07 9:09 ` Javier Martinez Canillas
2023-06-07 9:09 ` Javier Martinez Canillas
2023-06-05 14:48 ` [PATCH 18/30] fbdev/radeonfb: Use hardware device as backlight parent Thomas Zimmermann
2023-06-05 14:48 ` Thomas Zimmermann
2023-06-06 5:28 ` Dan Carpenter
2023-06-06 5:28 ` Dan Carpenter
2023-06-06 7:30 ` Thomas Zimmermann
2023-06-06 7:30 ` Thomas Zimmermann
2023-06-07 9:10 ` Javier Martinez Canillas
2023-06-07 9:10 ` Javier Martinez Canillas
2023-06-05 14:48 ` [PATCH 19/30] fbdev/rivafb: Reorder backlight and framebuffer init/cleanup Thomas Zimmermann
2023-06-05 14:48 ` Thomas Zimmermann
2023-06-07 9:11 ` Javier Martinez Canillas
2023-06-05 14:48 ` [PATCH 20/30] fbdev/rivafb: Use hardware device as backlight parent Thomas Zimmermann
2023-06-05 14:48 ` Thomas Zimmermann
2023-06-07 9:11 ` Javier Martinez Canillas
2023-06-07 9:11 ` Javier Martinez Canillas
2023-06-05 14:48 ` [PATCH 21/30] fbdev/sm501fb: Output message with fb_err() Thomas Zimmermann
2023-06-05 14:48 ` Thomas Zimmermann
2023-06-07 9:12 ` Javier Martinez Canillas
2023-06-05 14:48 ` [PATCH 22/30] fbdev/smscufx: Detect registered fb_info from refcount Thomas Zimmermann
2023-06-05 14:48 ` Thomas Zimmermann
2023-06-07 22:22 ` Javier Martinez Canillas
2023-06-07 22:22 ` Javier Martinez Canillas
2023-06-12 10:19 ` Thomas Zimmermann
2023-06-12 10:40 ` Javier Martinez Canillas
2023-06-05 14:48 ` [PATCH 23/30] fbdev/tdfxfb: Set i2c adapter parent to hardware device Thomas Zimmermann
2023-06-05 14:48 ` Thomas Zimmermann
2023-06-07 22:23 ` Javier Martinez Canillas
2023-06-07 22:23 ` Javier Martinez Canillas
2023-06-05 14:48 ` [PATCH 24/30] fbdev/core: Pass Linux device to pm_vt_switch_*() functions Thomas Zimmermann
2023-06-05 14:48 ` Thomas Zimmermann
2023-06-07 19:25 ` Sam Ravnborg
2023-06-07 19:25 ` Sam Ravnborg
2023-06-05 14:48 ` [PATCH 25/30] fbdev/core: Move framebuffer and backlight helpers into separate files Thomas Zimmermann
2023-06-05 14:48 ` Thomas Zimmermann
2023-06-07 19:38 ` Sam Ravnborg
2023-06-07 19:38 ` Sam Ravnborg
2023-06-09 7:19 ` Thomas Zimmermann
2023-06-09 7:19 ` Thomas Zimmermann
2023-06-05 14:48 ` [PATCH 26/30] fbdev/core: Add fb_device_{create,destroy}() Thomas Zimmermann
2023-06-05 14:48 ` Thomas Zimmermann
2023-06-07 19:45 ` Sam Ravnborg
2023-06-07 19:45 ` Sam Ravnborg
2023-06-05 14:48 ` [PATCH 27/30] fbdev/core: Move procfs code to separate file Thomas Zimmermann
2023-06-05 14:48 ` Thomas Zimmermann
2023-06-07 20:33 ` Sam Ravnborg
2023-06-07 20:33 ` Sam Ravnborg
2023-06-05 14:48 ` [PATCH 28/30] fbdev/core: Move file-I/O code into " Thomas Zimmermann
2023-06-05 14:48 ` Thomas Zimmermann
2023-06-05 21:35 ` kernel test robot
2023-06-05 21:35 ` kernel test robot
2023-06-07 20:48 ` Sam Ravnborg
2023-06-07 20:48 ` Sam Ravnborg
2023-06-12 10:35 ` Thomas Zimmermann
2023-06-12 10:35 ` Thomas Zimmermann
2023-06-07 22:28 ` Javier Martinez Canillas
2023-06-07 22:28 ` Javier Martinez Canillas
2023-06-05 14:48 ` [PATCH 29/30] fbdev/core: Rework fb init code Thomas Zimmermann
2023-06-05 14:48 ` Thomas Zimmermann
2023-06-07 20:51 ` Sam Ravnborg
2023-06-07 20:51 ` Sam Ravnborg
2023-06-05 14:48 ` [PATCH 30/30] fbdev: Make support for userspace interfaces configurable Thomas Zimmermann
2023-06-05 14:48 ` Thomas Zimmermann
2023-06-05 15:03 ` Greg KH
2023-06-05 15:03 ` Greg KH
2023-06-05 21:45 ` kernel test robot
2023-06-05 21:45 ` kernel test robot
2023-06-07 8:48 ` Geert Uytterhoeven
2023-06-07 8:48 ` Geert Uytterhoeven
2023-06-07 15:15 ` Thomas Zimmermann
2023-06-07 15:15 ` Thomas Zimmermann
2023-06-07 15:24 ` Geert Uytterhoeven
2023-06-07 15:24 ` Geert Uytterhoeven
2023-06-07 23:07 ` Javier Martinez Canillas [this message]
2023-06-07 23:07 ` Javier Martinez Canillas
2023-06-09 7:09 ` Thomas Zimmermann
2023-06-09 7:09 ` Thomas Zimmermann
2023-06-09 7:29 ` Geert Uytterhoeven
2023-06-09 7:29 ` Geert Uytterhoeven
2023-06-09 8:00 ` Thomas Zimmermann
2023-06-09 8:00 ` Thomas Zimmermann
2023-06-09 9:14 ` Geert Uytterhoeven
2023-06-09 9:14 ` Geert Uytterhoeven
2023-06-09 11:04 ` Thomas Zimmermann
2023-06-09 11:04 ` Thomas Zimmermann
2023-06-09 11:22 ` Geert Uytterhoeven
2023-06-09 11:22 ` Geert Uytterhoeven
2023-06-09 9:59 ` Javier Martinez Canillas
2023-06-09 9:59 ` Javier Martinez Canillas
2023-06-09 10:10 ` Geert Uytterhoeven
2023-06-09 10:10 ` Geert Uytterhoeven
2023-06-09 10:24 ` Javier Martinez Canillas
2023-06-09 10:24 ` Javier Martinez Canillas
2023-06-09 11:27 ` Javier Martinez Canillas
2023-06-09 11:27 ` Javier Martinez Canillas
2023-06-11 16:37 ` Sam Ravnborg
2023-06-11 16:37 ` Sam Ravnborg
2023-06-12 6:47 ` Thomas Zimmermann
2023-06-12 6:47 ` Thomas Zimmermann
2023-06-12 7:00 ` Thomas Zimmermann
2023-06-12 7:00 ` Thomas Zimmermann
2023-06-07 8:35 ` [PATCH 00/30] fbdev: Make userspace interfaces optional Geert Uytterhoeven
2023-06-07 8:35 ` Geert Uytterhoeven
2023-06-12 10:46 ` Thomas Zimmermann
2023-06-12 10:46 ` Thomas Zimmermann
2023-06-07 12:06 ` Markus Elfring
2023-06-07 12:06 ` Markus Elfring
2023-06-07 12:21 ` Thomas Zimmermann
2023-06-07 12:21 ` Thomas Zimmermann
2023-06-07 14:08 ` Markus Elfring
2023-06-07 14:08 ` Markus Elfring
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