.. so that KMSDRM_CreateDevice() can fail and SDL_VideoInit() would
move on to next bootstrap member which is kmsdrm_legacy. hopefully
fixes bug #5393.
Specifically this patch which does not invoke _AC_PATH_X_XMKMF and
_AC_PATH_X_DIRECT internal autoconf routines when cross-compiling:
http://git.savannah.gnu.org/gitweb/?p=autoconf.git;a=commitdiff;h=33c3a47c04ab70a4dd54963fe433a171bc03747f
Without this, CFLAGS would brokenly have system include paths like
-I/usr/include/X11 when cross-compiling e.g. for windows. (And it
also resulted in annoying imake crashes for my setup...)
Substring
I was trying the KMSDRM video backend with some very simple programs that were working ok on 2.0.12. The same code won?t work on the current dev branch and I get:
DEBUG: check_modesetting: probing ?/dev/dri/card0?
DEBUG: /dev/dri/card0 connector, encoder and CRTC counts are: 4 5 6
DEBUG: check_modesetting: probing ?/dev/dri/card0?
DEBUG: /dev/dri/card0 connector, encoder and CRTC counts are: 4 5 6
DEBUG: KMSDRM_VideoInit()
DEBUG: Opening device /dev/dri/card0
DEBUG: Opened DRM FD (3)
DEBUG: no atomic modesetting support.
DEBUG: Video subsystem has not been initialized
INFO: Using SDL video driver: (null)
DEBUG: Video subsystem has not been initialized
After carefully checking, the radeon driver doesn?t support atomic modesetting. That?s not the only problem : the same happens with the amdgpu driver if we disable Display Core (kernel parameter amdgpu.dc=0, which is required to get analogue outputs working).
This is a major regression in the KMSDRM driver.
Using atomic mode setting is great, but having no fallback to the "standard KMS" is bad.
Stephen Broadfoot
I've tracked this down to the following changeset bb65ba8e039b
https://hg.libsdl.org/SDL/diff/bb65ba8e039b/Makefile.in
this changeset renames the rule `build` to `build/.created` but the rule `install-lib` still depends on the rule `build`
This affects users who are trying to install via homebrew who are installing via source and not by the bottle as this invokes `make install`
To be clear, the error I was hitting when running make install is
make: *** No rule to make target `build', needed by `install-lib'. Stop.
pj5085
I added some printf to verify the math being done. Of the three joysticks I have, it works correctly for at least two, and seems to work correctly for the third. I say "seems to" because, for the third joystick, the values never go through the AxisCorrect function, and thus never hit my printf statements, even though they did in the version I wrote my patch against. I'm not sure what's going on there, but it at least seems to be working correctly in as much as I can tell.
I note this result in particular, for an SNES Gamepad (min=0, max=255):
Joystick value 0 becomes -32768
Joystick value 127 becomes 0
Joystick value 255 becomes 32767
Without the code that forces a zero point, the 127 input value would become -129, so I think you see why I added that code to turn it into zero. However, I think Kai Krakow has a point about how SDL shouldn't assume that there should be a center.
Obviously in the majority of cases there actually should be a center, and the code that turns that 127 into an actual 0 is creating only a 0.2% error over 0.4% of this joystick's range. However, what if there is an axis that is some kind of special control, like a 4-position switch, and, for whatever reason, the joystick reports it as an axis with 4 possible values, 0 to 3? In that case, mutilating the two center values to the same value is much more of an error and and turns that 4-position switch into a 3-position switch. If any joystick does this with a 2-position switch, then this code would render that control entirely useless as it would report the same value with the switch in either position. Obviously the code could require that there be at least N possible values, to guess whether something is a proper axis or just some kind of switch, but the choice of N would be arbitrary and that's ugly.
I guess the real problem here is that my gamepad is just kind of broken. It should be reporting a range of -1 to +1 since that's what it actually does. Also, as Kai Krakow points out, it's probably not SDL's place to fix broken hardware. I'll add that, if SDL does fix broken hardware, it should probably actually know that it's broken rather than be merely guessing that it is.
So, to the extent that SDL is able to do stuff like this, perhaps it's something better left for the user to configure in some kind of config file.
configure output is practically unchanged. there are still lots of
AC_TRY_COMPILE/AC_TRY_LINK replacements needed to really eliminate
the warnings, but that's for another time.
pj5085
It occurred to me that my simple patch that comments out a few lines of code does not correctly remove the dead zone since the calculation presumably assumes the dead zone has been cut out of the range. Then, while looking into how to make it output the correct range of values, I realized SDL wasn't returning the correct range of values to begin with.
This line of code was already present:
printf("Values = { %d, %d, %d, %d, %d }\n", absinfo.value, absinfo.minimum, absinfo.maximum, absinfo.fuzz, absinfo.flat);
For my joystick this yeilds:
Values = { 0, -127, 127, 0, 15 }
Then this code calculates the coefficients:
In SDL1:
joystick->hwdata->abs_correct[i].coef[0] = (absinfo.maximum + absinfo.minimum) / 2 - absinfo.flat;
joystick->hwdata->abs_correct[i].coef[1] = (absinfo.maximum + absinfo.minimum) / 2 + absinfo.flat;
t = ((absinfo.maximum - absinfo.minimum) / 2 - 2 * absinfo.flat);
if ( t != 0 ) {
joystick->hwdata->abs_correct[i].coef[2] = (1 << 29) / t;
} else {
joystick->hwdata->abs_correct[i].coef[2] = 0;
}
In SDL2:
joystick->hwdata->abs_correct[i].coef[0] = (absinfo.maximum + absinfo.minimum) - 2 * absinfo.flat;
joystick->hwdata->abs_correct[i].coef[1] = (absinfo.maximum + absinfo.minimum) + 2 * absinfo.flat;
t = ((absinfo.maximum - absinfo.minimum) - 4 * absinfo.flat);
if (t != 0) {
joystick->hwdata->abs_correct[i].coef[2] = (1 << 28) / t;
} else {
joystick->hwdata->abs_correct[i].coef[2] = 0;
}
Neither calculates the correct coefficients for the code in the AxisCorrect function.
In SDL1:
if ( value > correct->coef[0] ) {
if ( value < correct->coef[1] ) {
return 0;
}
value -= correct->coef[1];
} else {
value -= correct->coef[0];
}
value *= correct->coef[2];
value >>= 14;
In SDL2:
value *= 2;
if (value > correct->coef[0]) {
if (value < correct->coef[1]) {
return 0;
}
value -= correct->coef[1];
} else {
value -= correct->coef[0];
}
In SDL1, the calculated coefficients are coef[0]=15, coef[1]=-15 and coef[2]=5534751. So with a full-scale input of 127, it calculates an output value of 37835, which is considerably out of range.
In SDL2, the calculated coefficients are coef[0]=30, coef[1]=-30, and coef[2]=1383687. So with a full-scale input of 127, it calculates the same output value of 37835.
I tested it with the 3 joysticks I have, and it produces out-of-range values for all of them.
Anyway, since dead zones are garbage, I just deleted all of that junk and wrote some code that takes the absinfo.minimum and absinfo.maximum values and uses them to scale the axis range to -32767 through +32767.
I also made it detect when a range doesn't have an integer center point, e.g. the center of -128 to + 127 is -0.5. In such cases, if either value to the side of the center is provided, it zeros it, but it otherwise doesn't implement any kind of dead zone. This seemed important with my gamepad which provides only the values of 0, 127, and 255, since without this hack it would never be centered.
Also, the previous minimum output value was -32768, but as that creates an output range that has no true center, I changed the minimum value to -32767.
I tested it with the 3 joystick devices I have and it seems to create correct values for all of them.
Ozkan Sezer
Manuel Alfayate Corchete
Sam Lantinga
Ethan Lee