On Wed, Jul 15, 2026 at 12:11:12PM -0400, Michael S. Tsirkin wrote: > On Wed, Jul 15, 2026 at 06:07:56PM +0200, Hari Mishal wrote: > > On Wed, Jul 15, 2026 at 5:50 PM Michael S. Tsirkin <[email protected]> wrote: > > > > > > On Wed, Jul 15, 2026 at 04:22:41PM +0200, Hari Mishal wrote: > > > > nslots is derived from the ABS_MT_SLOT maximum reported by the > > > > virtio device. A device could report a bogus maximum (e.g. -1) > > > > making nslots = 0, which input_mt_init_slots() does not reject; > > > > it returns success without allocating any slot storage, silently > > > > leaving the device registered as multitouch capable with no > > > > backing state. > > > > > > So let's disable multitouch instead? > > > > > > > So rather than failing the whole probe, just warn and clear > > ABS_MT_SLOT from absbit in that case, so the rest of the device > > still registers? I took my lead from input_mt_init_slots(), which > > has its own internal cap and returns -EINVAL when the device > > reports more than 1024 slots. > > Shall I modify that case to get the same "warn and disable > > multitouch" for consistency, or is a hard failure better there since > > it's a different type of bad device data? > > I don't really know enough for sure but generally if the device can > kinda work it's better than not working, and adding > a capability to a device that driver can't use should > generally just ignore the capability, not fail probe.
What is the failure mode if we keep the ABS_MT_SLOT capability? Does the kernel crash? And if this can cause crash then we should fix input_mt_init_slots() to reject requests for 0 slots with -EINVAL. Thanks. -- Dmitry
