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Ivan Mironov
8b99f1705b
commit62d85b3bf9upstream. SDL 1.2 sets all fields related to the pixel format to zero in some cases[1]. Prior to commitdb05c48197("drm: fb-helper: Reject all pixel format changing requests"), there was an unintentional workaround for this that existed for more than a decade. First in device-specific DRM drivers, then here in drm_fb_helper.c. Previous code containing this workaround just ignores pixel format fields from userspace code. Not a good thing either, as this way, driver may silently use pixel format different from what client actually requested, and this in turn will lead to displaying garbage on the screen. I think that returning EINVAL to userspace in this particular case is the right option, so I decided to left code from problematic commit untouched instead of just reverting it entirely. Here is the steps required to reproduce this problem exactly: 1) Compile fceux[2] with SDL 1.2.15 and without GTK or OpenGL support. SDL should be compiled with fbdev support (which is on by default). 2) Create /etc/fb.modes with following contents (values seems not used, and just required to trigger problematic code in SDL): mode "test" geometry 1 1 1 1 1 timings 1 1 1 1 1 1 1 endmode 3) Create ~/.fceux/fceux.cfg with following contents: SDL.Hotkeys.Quit = 27 SDL.DoubleBuffering = 1 4) Ensure that screen resolution is at least 1280x960 (e.g. append "video=Virtual-1:1280x960-32" to the kernel cmdline for qemu/QXL). 5) Try to run fceux on VT with some ROM file[3]: # ./fceux color_test.nes [1] SDL 1.2.15 source code, src/video/fbcon/SDL_fbvideo.c, FB_SetVideoMode() [2] http://www.fceux.com [3] Example ROM: https://github.com/bokuweb/rustynes/blob/master/roms/color_test.nes Reported-by: saahriktu <mail@saahriktu.org> Suggested-by: saahriktu <mail@saahriktu.org> Cc: stable@vger.kernel.org Fixes:db05c48197("drm: fb-helper: Reject all pixel format changing requests") Signed-off-by: Ivan Mironov <mironov.ivan@gmail.com> [danvet: Delete misleading comment.] Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch> Link: https://patchwork.freedesktop.org/patch/msgid/20190108072353.28078-2-mironov.ivan@gmail.com Link: https://patchwork.freedesktop.org/patch/msgid/20190108072353.28078-2-mironov.ivan@gmail.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.