On Mon, May 27, 2024 at 03:55:57PM -0400, Jason Andryuk wrote: > From: Dmitry Torokhov <dmitry.torokhov@xxxxxxxxx> > > commit 0774d19038c496f0c3602fb505c43e1b2d8eed85 upstream. > > If an input device declares too many capability bits then modalias > string for such device may become too long and not fit into uevent > buffer, resulting in failure of sending said uevent. This, in turn, > may prevent userspace from recognizing existence of such devices. > > This is typically not a concern for real hardware devices as they have > limited number of keys, but happen with synthetic devices such as > ones created by xen-kbdfront driver, which creates devices as being > capable of delivering all possible keys, since it doesn't know what > keys the backend may produce. > > To deal with such devices input core will attempt to trim key data, > in the hope that the rest of modalias string will fit in the given > buffer. When trimming key data it will indicate that it is not > complete by placing "+," sign, resulting in conversions like this: > > old: k71,72,73,74,78,7A,7B,7C,7D,8E,9E,A4,AD,E0,E1,E4,F8,174, > new: k71,72,73,74,78,7A,7B,7C,+, > > This should allow existing udev rules continue to work with existing > devices, and will also allow writing more complex rules that would > recognize trimmed modalias and check input device characteristics by > other means (for example by parsing KEY= data in uevent or parsing > input device sysfs attributes). > > Note that the driver core may try adding more uevent environment > variables once input core is done adding its own, so when forming > modalias we can not use the entire available buffer, so we reduce > it by somewhat an arbitrary amount (96 bytes). > > Reported-by: Jason Andryuk <jandryuk@xxxxxxxxx> > Reviewed-by: Peter Hutterer <peter.hutterer@xxxxxxxxx> > Tested-by: Jason Andryuk <jandryuk@xxxxxxxxx> > Link: https://lore.kernel.org/r/ZjAWMQCJdrxZkvkB@xxxxxxxxxx > Cc: stable@xxxxxxxxxxxxxxx > Signed-off-by: Dmitry Torokhov <dmitry.torokhov@xxxxxxxxx> > [ Apply to linux-6.1.y ] > Signed-off-by: Jason Andryuk <jason.andryuk@xxxxxxx> > --- > Patch did not automatically apply to 6.1.y because > input_print_modalias_parts() does not have const on *id. > > Tested on 6.1. Seems to also apply and build on 5.4 and 4.19. How was this tested? It blows up the build on all branches, 6.1 and older kernels with a ton of errors like: drivers/input/input.c: In function ‘input_print_modalias_parts’: drivers/input/input.c:1397:40: error: passing argument 4 of ‘input_print_modalias_bits’ discards ‘const’ qualifier from pointer target type [-Werror=discarded-qualifiers] 1397 | 'e', id->evbit, 0, EV_MAX); | ~~^~~~~~~ And so on. Are you sure you sent the right patch? thanks, greg k-h
