On Tuesday 03 December 2019 00:09:47 Pali Rohár wrote: > On Monday 02 December 2019 11:36:28 Dmitry Torokhov wrote: > > On Mon, Dec 02, 2019 at 07:53:40PM +0100, Pali Rohár wrote: > > > On Monday 02 December 2019 09:54:40 Dmitry Torokhov wrote: > > > > On Mon, Dec 02, 2019 at 09:47:50AM +0100, Pali Rohár wrote: > > > > > On Sunday 01 December 2019 17:23:05 Dmitry Torokhov wrote: > > > > > > Hi Pali, > > > > > > > > > > > > On Sun, Dec 01, 2019 at 03:53:57PM +0100, Pali Rohár wrote: > > > > > > > Hello! > > > > > > > > > > > > > > On Wednesday 27 November 2019 10:51:39 Abhishek Pandit-Subedi wrote: > > > > > > > > Support setting the uniq attribute of the input device. The uniq > > > > > > > > attribute is used as a unique identifier for the connected device. > > > > > > > > > > > > > > > > For example, uinput devices created by BlueZ will store the address of > > > > > > > > the connected device as the uniq property. > > > > > > > > > > > > > > > > Signed-off-by: Abhishek Pandit-Subedi > > > > > > > > > > > > > > ... > > > > > > > > > > > > > > > diff --git a/include/uapi/linux/uinput.h b/include/uapi/linux/uinput.h > > > > > > > > index c9e677e3af1d..d5b7767c1b02 100644 > > > > > > > > --- a/include/uapi/linux/uinput.h > > > > > > > > +++ b/include/uapi/linux/uinput.h > > > > > > > > @@ -145,6 +145,7 @@ struct uinput_abs_setup { > > > > > > > > #define UI_SET_PHYS _IOW(UINPUT_IOCTL_BASE, 108, char*) > > > > > > > > #define UI_SET_SWBIT _IOW(UINPUT_IOCTL_BASE, 109, int) > > > > > > > > #define UI_SET_PROPBIT _IOW(UINPUT_IOCTL_BASE, 110, int) > > > > > > > > +#define UI_SET_UNIQ _IOW(UINPUT_IOCTL_BASE, 111, char*) > > > > > > > > > > > > > > I think that usage of char* as type in _IOW would cause compatibility > > > > > > > problems like it is for UI_SET_PHYS (there is UI_SET_PHYS_COMPAT). Size > > > > > > > of char* pointer depends on userspace (32 vs 64bit), so 32bit process on > > > > > > > 64bit kernel would not be able to call this new UI_SET_UNIQ ioctl. > > > > > > > > > > > > > > I would suggest to define this ioctl as e.g.: > > > > > > > > > > > > > > #define UI_SET_UNIQ _IOW(_IOC_WRITE, UINPUT_IOCTL_BASE, 111, 0) > > > > > > > > > > > > > > And then in uinput.c code handle it as: > > > > > > > > > > > > > > case UI_SET_UNIQ & ~IOCSIZE_MASK: > > > > > > > > > > > > > > as part of section /* Now check variable-length commands */ > > > > > > > > > > > > If we did not have UI_SET_PHYS in its current form, I'd agree with you, > > > > > > but I think there is benefit in having UI_SET_UNIQ be similar to > > > > > > UI_SET_PHYS. > > > > > > > > > > I thought that ioctl is just number, so we can define it as we want. And > > > > > because uinput.c has already switch for variable-length commands it > > > > > would be easy to use it. Final handling can be in separate function like > > > > > for UI_SET_PHYS which can look like same. > > > > > > > > Yes, we can define ioctl number as whatever we want. What I was trying > > > > to say, right now users do this: > > > > > > > > rc = ioctl(fd, UI_SET_PHYS, "whatever"); > > > > ... > > > > > > > > and with UI_SET_UNIQ they expect the following to work: > > > > > > > > rc = ioctl(fd, UI_SET_UNIQ, "whatever"); > > > > ... > > > > > > And would not following definition > > > > > > #define UI_SET_UNIQ _IOW(_IOC_WRITE, UINPUT_IOCTL_BASE, 111, 0) > > > > > > allow userspace to call > > > > > > rc = ioctl(fd, UI_SET_UNIQ, "whatever"); > > > > > > as you want? > > > > OK, so what you are saying is that we can have whatever in the size > > portion of ioctl number and simply ignore it in the driver > > Yes. > > > (and I do not > > think we need to do any of "UI_SET_UNIQ & ~IOCSIZE_MASK" really). > > You are right, we do not need to clear any IOCSIZE_MASK. As ioctl number > would be always sam constant number. So it would be really simple. So > original patch would work if UI_SET_UNIQ define would be changed to > above with _IOW() macro. > > > While this would work, I am not sure it is the best option as I think > > we'd have to comment extensively why we have arbitrary number in place > > of the size. > > Comment can be added. But this is as ioctl is going to accept variable > length array (not fixed array), zero value make sense for me (zero as we > do not know exact size). > > > And we still do not really save anything, as we still have to go through > > compat ioctl handler (since we have it already) and it is very simple to > > add a case for UI_SET_UNIQ there... > > Yes, compat ioctl is still used. But my proposed solution does not > involve to define a new compact ioctl number just for sizeof(char *). > > I'm looking at this particular problem from side, that there is no > reason to define two new ioctl numbers for UI_SET_UNIQ (one normal > number and one compat number), when one number is enough. It is one new > ioctl call, so one ioctl number should be enough. > > And also with my proposed solution with ioctl size=0 it simplify > implementation of UI_SET_UNIQ as it is not needed to implement also > UI_SET_UNIQ_COMPAT ioctl nor touch compat ioct code path. Basically > original patch (with changed UI_SET_UNIQ macro) is enough. > > But of of course, this is my view of this problem and I would not be > against your decision from maintainer position. Both solutions would > work correctly and bring same behavior for userspace applications. Hi Dmitry! I was looking again at those _IOW defines for ioctl calls and I have another argument why not specify 'char *' in _IOW: All ioctls in _IOW() specify as a third macro argument type which is passed as pointer to the third argument for ioctl() syscall. So e.g.: #define EVIOCSCLOCKID _IOW('E', 0xa0, int) is called from userspace as: int val; ioctl(fd, EVIOCSCLOCKID, &val); Or #define EVIOCSMASK _IOW('E', 0x93, struct input_mask) is called as: struct input_mask val; ioctl(fd, EVIOCSMASK, &val); So basically third argument for _IOW specify size of byte buffer passed as third argument for ioctl(). In _IOW is not specified pointer to struct input_mask, but struct input_mask itself. And in case you define #define MY_NEW_IOCTL _IOW(UINPUT_IOCTL_BASE, 200, char*) then you by above usage you should pass data as: char *val = "DATA"; ioctl(fd, MY_NEW_IOCTL, &val); Which is not same as just: ioctl(fd, MY_NEW_IOCTL, "DATA"); As in former case you passed pointer to pointer to data and in later case you passed only pointer to data. It just mean that UI_SET_PHYS is already defined inconsistently which is also reason why compat ioctl for it was introduced. -- Pali Rohár pali.rohar@gmail.com