Hi,
Originally this issue was brought up on linux.org.ru forum by user saahriktu, he is on Cc. He discovered that commit db05c48197759 ("drm: fb-helper: Reject all pixel format changing requests") breaks support of SDL1 programs, like various old games and emulators of old game consoles. First patch contains fix for that commit.
I tried to reproduce the same issue in a VM under qemu, and found yet another part of kernel code which prevents SDL1 apps from running normally. Second patch in this series fixes this problem.
Also, it seems that at least in some cases both problems could be circumvented by adding appropriate modes into /etc/fb.modes. But without examining the kernel code it is not clear which values are correct. I am not sure that such circumvention covers all possible cases, and it is definitely far from any user-frienliness.
First patch in this series fixes a clear regression. Second patch is optional, please read commit message carefully before applying it.
Changes in v1: - Added "Cc: stable" to the patch which fixes known regression. - Added more information and detailed reproduction steps in commit messages.
Changes in v0: - RFC patch series introduced.
Ivan Mironov (2): drm/fb-helper: Bring back workaround for bugs of SDL 1.2 drm/fb-helper: Ignore the value of fb_var_screeninfo.pixclock
drivers/gpu/drm/drm_fb_helper.c | 153 +++++++++++++++++++++----------- 1 file changed, 99 insertions(+), 54 deletions(-)