4.20-stable review patch. If anyone has any objections, please let me know.
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From: Ivan Mironov mironov.ivan@gmail.com
commit 62d85b3bf9d978ed4b6b2aeef5cf0ccf1423906e upstream.
SDL 1.2 sets all fields related to the pixel format to zero in some cases[1]. Prior to commit db05c48197759 ("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: db05c48197759 ("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... Link: https://patchwork.freedesktop.org/patch/msgid/20190108072353.28078-2-mironov... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/gpu/drm/drm_fb_helper.c | 126 +++++++++++++++++++++++----------------- 1 file changed, 73 insertions(+), 53 deletions(-)
--- a/drivers/gpu/drm/drm_fb_helper.c +++ b/drivers/gpu/drm/drm_fb_helper.c @@ -1621,6 +1621,64 @@ static bool drm_fb_pixel_format_equal(co var_1->transp.msb_right == var_2->transp.msb_right; }
+static void drm_fb_helper_fill_pixel_fmt(struct fb_var_screeninfo *var, + u8 depth) +{ + switch (depth) { + case 8: + var->red.offset = 0; + var->green.offset = 0; + var->blue.offset = 0; + var->red.length = 8; /* 8bit DAC */ + var->green.length = 8; + var->blue.length = 8; + var->transp.offset = 0; + var->transp.length = 0; + break; + case 15: + var->red.offset = 10; + var->green.offset = 5; + var->blue.offset = 0; + var->red.length = 5; + var->green.length = 5; + var->blue.length = 5; + var->transp.offset = 15; + var->transp.length = 1; + break; + case 16: + var->red.offset = 11; + var->green.offset = 5; + var->blue.offset = 0; + var->red.length = 5; + var->green.length = 6; + var->blue.length = 5; + var->transp.offset = 0; + break; + case 24: + var->red.offset = 16; + var->green.offset = 8; + var->blue.offset = 0; + var->red.length = 8; + var->green.length = 8; + var->blue.length = 8; + var->transp.offset = 0; + var->transp.length = 0; + break; + case 32: + var->red.offset = 16; + var->green.offset = 8; + var->blue.offset = 0; + var->red.length = 8; + var->green.length = 8; + var->blue.length = 8; + var->transp.offset = 24; + var->transp.length = 8; + break; + default: + break; + } +} + /** * drm_fb_helper_check_var - implementation for &fb_ops.fb_check_var * @var: screeninfo to check @@ -1651,6 +1709,20 @@ int drm_fb_helper_check_var(struct fb_va }
/* + * Workaround for SDL 1.2, which is known to be setting all pixel format + * fields values to zero in some cases. We treat this situation as a + * kind of "use some reasonable autodetected values". + */ + if (!var->red.offset && !var->green.offset && + !var->blue.offset && !var->transp.offset && + !var->red.length && !var->green.length && + !var->blue.length && !var->transp.length && + !var->red.msb_right && !var->green.msb_right && + !var->blue.msb_right && !var->transp.msb_right) { + drm_fb_helper_fill_pixel_fmt(var, fb->format->depth); + } + + /* * drm fbdev emulation doesn't support changing the pixel format at all, * so reject all pixel format changing requests. */ @@ -1961,59 +2033,7 @@ void drm_fb_helper_fill_var(struct fb_in info->var.yoffset = 0; info->var.activate = FB_ACTIVATE_NOW;
- switch (fb->format->depth) { - case 8: - info->var.red.offset = 0; - info->var.green.offset = 0; - info->var.blue.offset = 0; - info->var.red.length = 8; /* 8bit DAC */ - info->var.green.length = 8; - info->var.blue.length = 8; - info->var.transp.offset = 0; - info->var.transp.length = 0; - break; - case 15: - info->var.red.offset = 10; - info->var.green.offset = 5; - info->var.blue.offset = 0; - info->var.red.length = 5; - info->var.green.length = 5; - info->var.blue.length = 5; - info->var.transp.offset = 15; - info->var.transp.length = 1; - break; - case 16: - info->var.red.offset = 11; - info->var.green.offset = 5; - info->var.blue.offset = 0; - info->var.red.length = 5; - info->var.green.length = 6; - info->var.blue.length = 5; - info->var.transp.offset = 0; - break; - case 24: - info->var.red.offset = 16; - info->var.green.offset = 8; - info->var.blue.offset = 0; - info->var.red.length = 8; - info->var.green.length = 8; - info->var.blue.length = 8; - info->var.transp.offset = 0; - info->var.transp.length = 0; - break; - case 32: - info->var.red.offset = 16; - info->var.green.offset = 8; - info->var.blue.offset = 0; - info->var.red.length = 8; - info->var.green.length = 8; - info->var.blue.length = 8; - info->var.transp.offset = 24; - info->var.transp.length = 8; - break; - default: - break; - } + drm_fb_helper_fill_pixel_fmt(&info->var, fb->format->depth);
info->var.xres = fb_width; info->var.yres = fb_height;