On 11/20/23 22:54, Thomas Zimmermann via openSUSE Factory wrote:
Hi
Am 20.11.23 um 13:18 schrieb Simon Lees:
On 11/20/23 21:45, Michal Suchánek wrote:
On Mon, Nov 20, 2023 at 12:42:02PM +1030, Simon Lees wrote:
On 11/14/23 18:36, Thomas Zimmermann via openSUSE Factory wrote:
Hi
Am 02.11.23 um 07:45 schrieb Simon Lees:
Hi,
Sorry I missed this thread while I was travelling
On 10/10/23 18:56, Thomas Zimmermann via openSUSE Factory wrote: > tl;dr: Disable fbdev userspace interfaces on TW > > Hi, > > the upcoming Linux kernel v6.6 will contain the option to > disable fbdev userspace interfaces in the kernel configuration. > [1] I intent to enable this and thereby switch off /dev/fb0 et > al. The tracker bug is boo#1212947. [2] > > * Why? The old fbdev subsystem is an endless source of bugs. > For example, we recently had an out-of-bounds access in the > fbdev emulation, where userspace could write beyond the end of > the framebuffer memory. [3] Fbdev is under-maintained. I've been > doing improvements in recent kernel releases, but only where it > benefits the DRM subsystem. > Disabling fbdev userspace interfaces will also help weeding out > any programs that still contain hard dependencies on them. > > * What changes? Enabling the new kernel option disables all > fbdev userspace interfaces. These are > > * the device files, such as /dev/fb0 > * the sys files under /sys/class/graphics/fb[0-9]+ > * /proc/fb > > * What are the effects on userspace programs? Userspace > applications run on the desktop via Wayland or X. There will be > no change to them. Xorg and Wayland compositors run on DRM > interfaces. A few programs run on SDL, which has no dependency > on fbdev either. Any fbdev support in these mid-layer > components should be disabled as well. > > There's one known affected program: TW's text-mode installer can > use the tool fbiterm to display CJK symbols during installation. > This comes from a time when some low-end systems where not able > to boot graphics installation. fbiterm has been unmaintained for >> 15 years and is ready for retirement. But there's no good > drop-in replacement. I propose to simply remove fbiterm and let > the graphics installer handle CJK. > > * What about the framebuffer console? The kernel-provided > framebuffer console does not change. The kernel will still show > the regular console. > Userspace interfaces in /sys/class/graphics/fbcon are still > available. > > For questions and discussion, please comment here or in boo#1212947. I have usecases with raspberry pi's and other similar devices where I have used SPI based TFT displays outputting directly to /dev/fb0, In particular I have used "fbi" to draw images directly to the framebuffer, efl (Enlightenment Foundation Libraries) apps can also render directly to the framebuffer.
I haven't had mine working that recently so I can't comment on the state of the driver I was using but given the prevalence of such devices in the raspberry pi ecosystem it probably makes alot of sense to keep this feature enabled atleast for ARM kernels.
Which displays (brand, model) do you use?
Do you need a new driver for the displays? Or do you need a user space that does not require /dev/fb?
Sorry for taking a while to get back to you, i'm using a 3.2" waveshare spotpear [1], I last had it running with the fbdev driver (its a while since I updated the project.
Generally I have been using it with programs that can directly use /dev/fb1 rather then running a full X11 instance because its mostly just for displaying status messages etc, although during testing I setup a full X11 environment but generally most X11 desktop's don't work well on a screen that small and it makes my life simpler because I just setup X11 on the rpi's hdmi port for if I really want it to use more advanced debugging tools or to setup the network configuration etc.
Hello,
does the driver for this display sypport DRM?
Not last time I checked, hence the need for /dev/fb*
Which driver are you using?
Currently fbdev, i've seen similarly designed newer displays using tinyDRM, so that maybe an alternative but to date I couldn't find any information of someone implementing support for this display in that driver. -- Simon Lees (Simotek) http://simotek.net Emergency Update Team keybase.io/simotek SUSE Linux Adelaide Australia, UTC+10:30 GPG Fingerprint: 5B87 DB9D 88DC F606 E489 CEC5 0922 C246 02F0 014B