Em Mon, 27 Jun 2022 15:18:12 +0100 Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx> escreveu: > On Sun, 26 Jun 2022 23:33:31 +0100 > Mauro Carvalho Chehab <mchehab@xxxxxxxxxx> wrote: > > > Em Sun, 26 Jun 2022 17:55:08 +0100 > > Jonathan Cameron <jic23@xxxxxxxxxx> escreveu: > > > > > From: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx> > > > > > > The kernel build docs do not support having multiple definitions for > > > the same sysfs filename. > > > > Actually, this is not a matter of the docs build system not supporting. > > It is, instead, how the ABI were supposed to work: a given ABI symbol > > should have consistent behavior on all drivers that use it. Failing to > > do that is asking for troubles. > > > > So, having duplicated symbols either mean that: > > > > a) both have the same meaning. They can/should be unified in order to > > remove redundant documentation; > > > > b) the same ABI symbol have different meanings depending on the driver(s) > > that use it. This makes very hard for userspace, as it is harder to > > write a program using it, as the behavior/meaning starts to be > > driver-dependent. > > I think we'll disagree on this. > > There are circumstances where a particular ABI in a particular driver > benefits from additional documentation that would be in the 'impdef > category' for the generic ABI. If a particular driver needs something different, either: 1. the ABI definition was loose or too tight, not being generic enough to cover other hardware needing ABI for the same feature; 2. a different ABI symbol would need, as the two symbols with the same name are mapping completely different ABIs. > For this particular case it extends the info available from 'wire > disconnected' in the generic case, to 'which possible wires are > disconnected' in the specific case. In the specific case of device faults, it could be mapped in a way that would be generic enough, yet providing hardware-specific information, when the hardware supports it. In this specific case, I would probably create a generic ABI (or ABI set) to report hardware issues in a way that it would be more generic. One possibility for this case would be to use something like this: $ cat /sys/bus/iio/devices/iio:deviceX/fault no faults On hardware that can't pinpoint what wire(s) the problem is occurring: $ cat /sys/bus/iio/devices/iio:deviceX/fault fault: open circuit or $ cat /sys/bus/iio/devices/iio:deviceX/fault fault: excessive voltage On more sophisticated hardware that can pinpoint what wires have issues, it may report, instead: $ cat /sys/bus/iio/devices/iio:deviceX/fault fault: open circuit fault at thermocouple wire #2 or $ cat /sys/bus/iio/devices/iio:deviceX/fault fault: excessive voltage at thermocouple wires #0 and #1 or even: $ cat /sys/bus/iio/devices/iio:deviceX/fault fault: open circuit fault at thermocouple wire #2 fault: excessive voltage at thermocouple wires #0 and #1 The above should be generic enough for a program to identify if there isn't any failures if such "fault" ABI would return "no faults". Any value different than that means that there's a fault, and the read value telling what happened could be output to the user before such program aborts due to a hardware error. - The point is that, when the ABI is made to be subsystem-wide since the beginning, it tends to be more generic, as the ABI design should consider that other devices may have different capabilities. > Neither affects what userspace > does with it, but they are useful if you are debugging the hardware. > They are probably not worth expanding the ABI to provide a debugging > guide, so it that info was in the documentation but is now lost > (in this case, non critical as it's probably a case of go read the > datasheet if the hanging wire isn't obvious). > > I don't mind just making this patch description vague: > > Kernel documentation for a given ABI element should not be duplicated > in multiple files, so pull them into one higher level documentation file. Works for me. With that, feel free to add my reviewed-by. Regards, Mauro > > > Hence generalize the documentation a little > > > and pull it out of device specific files and into > > > sysfs-bus-iio-thermocouple > > > > > > These may well be more general and need pulling into a more generic > > > file in the future, but we can do that when it is needed. > > > > > > Signed-off-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx> > > > Cc: Navin Sankar Velliangiri <navin@xxxxxxxxxxx> > > > Cc: Paresh Chaudhary <paresh.chaudhary@xxxxxxxxxxxxxxxxxxx> > > > > Except for the above correction, the patch looks OK to me. > > > > Reviewed-by: Mauro Carvalho Chehab <mchehab@xxxxxxxxxx> > > > > > --- > > > .../sysfs-bus-iio-temperature-max31856 | 31 ------------------- > > > .../sysfs-bus-iio-temperature-max31865 | 12 ------- > > > .../ABI/testing/sysfs-bus-iio-thermocouple | 18 +++++++++++ > > > 3 files changed, 18 insertions(+), 43 deletions(-) > > > > > > diff --git a/Documentation/ABI/testing/sysfs-bus-iio-temperature-max31856 b/Documentation/ABI/testing/sysfs-bus-iio-temperature-max31856 > > > deleted file mode 100644 > > > index e5ef6d8e5da1..000000000000 > > > --- a/Documentation/ABI/testing/sysfs-bus-iio-temperature-max31856 > > > +++ /dev/null > > > @@ -1,31 +0,0 @@ > > > -What: /sys/bus/iio/devices/iio:deviceX/fault_oc > > > -KernelVersion: 5.1 > > > -Contact: linux-iio@xxxxxxxxxxxxxxx > > > -Description: > > > - Open-circuit fault. The detection of open-circuit faults, > > > - such as those caused by broken thermocouple wires. > > > - Reading returns either '1' or '0'. > > > - > > > - === ======================================================= > > > - '1' An open circuit such as broken thermocouple wires > > > - has been detected. > > > - '0' No open circuit or broken thermocouple wires are detected > > > - === ======================================================= > > > - > > > -What: /sys/bus/iio/devices/iio:deviceX/fault_ovuv > > > -KernelVersion: 5.1 > > > -Contact: linux-iio@xxxxxxxxxxxxxxx > > > -Description: > > > - Overvoltage or Undervoltage Input Fault. The internal circuitry > > > - is protected from excessive voltages applied to the thermocouple > > > - cables by integrated MOSFETs at the T+ and T- inputs, and the > > > - BIAS output. These MOSFETs turn off when the input voltage is > > > - negative or greater than VDD. > > > - > > > - Reading returns either '1' or '0'. > > > - > > > - === ======================================================= > > > - '1' The input voltage is negative or greater than VDD. > > > - '0' The input voltage is positive and less than VDD (normal > > > - state). > > > - === ======================================================= > > > diff --git a/Documentation/ABI/testing/sysfs-bus-iio-temperature-max31865 b/Documentation/ABI/testing/sysfs-bus-iio-temperature-max31865 > > > index 4b072da92218..349089e4f2d6 100644 > > > --- a/Documentation/ABI/testing/sysfs-bus-iio-temperature-max31865 > > > +++ b/Documentation/ABI/testing/sysfs-bus-iio-temperature-max31865 > > > @@ -1,15 +1,3 @@ > > > -What: /sys/bus/iio/devices/iio:deviceX/fault_ovuv > > > -KernelVersion: 5.11 > > > -Contact: linux-iio@xxxxxxxxxxxxxxx > > > -Description: > > > - Overvoltage or Undervoltage Input fault. The internal circuitry > > > - is protected from excessive voltages applied to the thermocouple > > > - cables at FORCE+, FORCE2, RTDIN+ & RTDIN-. This circuitry turn > > > - off when the input voltage is negative or greater than VDD. > > > - > > > - Reading returns '1' if input voltage is negative or greater > > > - than VDD, otherwise '0'. > > > - > > > What: /sys/bus/iio/devices/iio:deviceX/in_filter_notch_center_frequency > > > KernelVersion: 5.11 > > > Contact: linux-iio@xxxxxxxxxxxxxxx > > > diff --git a/Documentation/ABI/testing/sysfs-bus-iio-thermocouple b/Documentation/ABI/testing/sysfs-bus-iio-thermocouple > > > new file mode 100644 > > > index 000000000000..01259df297ca > > > --- /dev/null > > > +++ b/Documentation/ABI/testing/sysfs-bus-iio-thermocouple > > > @@ -0,0 +1,18 @@ > > > +What: /sys/bus/iio/devices/iio:deviceX/fault_ovuv > > > +KernelVersion: 5.1 > > > +Contact: linux-iio@xxxxxxxxxxxxxxx > > > +Description: > > > + Overvoltage or Undervoltage Input Fault. The internal circuitry > > > + is protected from excessive voltages applied to the thermocouple > > > + cables. The device can also detect if such a condition occurs. > > > + > > > + Reading returns '1' if input voltage is negative or greater > > > + than VDD, otherwise '0'. > > > + > > > +What: /sys/bus/iio/devices/iio:deviceX/fault_oc > > > +KernelVersion: 5.1 > > > +Contact: linux-iio@xxxxxxxxxxxxxxx > > > +Description: > > > + Open-circuit fault. The detection of open-circuit faults, > > > + such as those caused by broken thermocouple wires. > > > + Reading returns '1' if fault, '0' otherwise. >
