On 06/30/2014 02:25 PM, Christopher Friedt wrote: > On Mon, Jun 30, 2014 at 7:48 AM, Thomas Hellstrom <thellst...@vmware.com> > wrote: >> I don't think we can blame video-vmware for this. A kernel driver change >> that breaks existing user-space is by definition a kernel driver bug, >> regardless whether exisiting user-space is doing something horrendously >> stupid. > I wouldn't be so quick to say it's a kernel bug. The fbdev contract > hasn't changed. Also xf86-video-vmware isn't using the fbdev driver, > and the fbdev driver code is obviously correct (see screenshots in > link submitted with initial patch).
As I said. A kernel change that breaks existing user-space is ALWAYS BY DEFINITION a kernel bug. kernel changes are NOT ALLOWED to break existing user-space. The only exception I can see here is if someone uses the old non-kms driver which is not intended to work if vmware fbdev is loaded but that's not the case here, from what I can tell? > >> So the fix must IMO be a kernel driver fix. My initial guess is that >> once we set the bytes per line register, it might not be automatically >> updated when the screen width is changed, but the documentation is poor. >> I see if I can shed some light over this. > Having dumped all of the svga registers while hacking on vmwgfx, I > noticed that the BYTES_PER_LINE field is initially incorrectly set to > something way off. My initial reaction is that video-vmware doesn't > properly compute the bytes-per-line register, and therefore that it is > a video-vmware bug that has always existed. xf86-video-vmware in kms mode uses the kernel driver to set these registers. FWIW, the modesetting part of the kernel driver uses SVGA_REG_PITCHLOCK instead of SVGA_REG_BYTES_PER_LINE to set the pitch. That's probably where the clash happens. /Thomas > > I'm reproducing the problem and providing a fix for video-vmware as I > write this. > > C -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
