Messages in this thread | | | Subject | Re: [RFC PATCH 00/14] iio: buffer: add support for multiple buffers | From | Lars-Peter Clausen <> | Date | Mon, 11 May 2020 21:56:40 +0200 |
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On 5/11/20 4:56 PM, Ardelean, Alexandru wrote: > On Mon, 2020-05-11 at 15:58 +0200, Lars-Peter Clausen wrote: >> [External] >> >> On 5/11/20 3:24 PM, Ardelean, Alexandru wrote: >>> On Mon, 2020-05-11 at 13:03 +0000, Ardelean, Alexandru wrote: >>>> [External] >>>> >>>> On Mon, 2020-05-11 at 12:37 +0200, Lars-Peter Clausen wrote: >>>>> [External] >>>>> >>>>> On 5/11/20 12:33 PM, Ardelean, Alexandru wrote: >>>>>> On Sun, 2020-05-10 at 11:09 +0100, Jonathan Cameron wrote: >>>>>>> [External] >>>>>>> >>>>>>> On Sat, 9 May 2020 10:52:14 +0200 >>>>>>> Lars-Peter Clausen <lars@metafoo.de> wrote: >>>>>>> >>>>>>>> On 5/8/20 3:53 PM, Alexandru Ardelean wrote: >>>>>>>>> [...] >>>>>>>>> What I don't like, is that iio:device3 has iio:buffer3:0 (to 3). >>>>>>>>> This is because the 'buffer->dev.parent = &indio_dev->dev'. >>>>>>>>> But I do feel this is correct. >>>>>>>>> So, now I don't know whether to leave it like that or symlink to >>>>>>>>> shorter >>>>>>>>> versions like 'iio:buffer3:Y' -> 'iio:device3/bufferY'. >>>>>>>>> The reason for naming the IIO buffer devices to 'iio:bufferX:Y' >>>>>>>>> is >>>>>>>>> mostly to make the names unique. It would have looked weird to >>>>>>>>> do >>>>>>>>> '/dev/buffer1' if I would have named the buffer devices >>>>>>>>> 'bufferX'. >>>>>>>>> >>>>>>>>> So, now I'm thinking of whether all this is acceptable. >>>>>>>>> Or what is acceptable? >>>>>>>>> Should I symlink 'iio:device3/iio:buffer3:0' -> >>>>>>>>> 'iio:device3/buffer0'? >>>>>>>>> What else should I consider moving forward? >>>>>>>>> What means forward? >>>>>>>>> Where did I leave my beer? >>>>>>>> Looking at how the /dev/ devices are named I think we can provide >>>>>>>> a >>>>>>>> name >>>>>>>> that is different from the dev_name() of the device. Have a look >>>>>>>> at >>>>>>>> device_get_devnode() in drivers/base/core.c. We should be able to >>>>>>>> provide the name for the chardev through the devnode() callback. >>>>>>>> >>>>>>>> While we are at this, do we want to move the new devices into an >>>>>>>> iio >>>>>>>> subfolder? So iio/buffer0:0 instead of iio:buffer0:0? >>>>>>> Possibly on the folder. I can't for the life of me remember why I >>>>>>> decided >>>>>>> not to do that the first time around - I'll leave it at the >>>>>>> mysterious "it may turn out to be harder than you'd think..." >>>>>>> Hopefully not ;) >>>>>> I was also thinking about the /dev/iio subfolder while doing this. >>>>>> I can copy that from /dev/input >>>>>> They seem to do it already. >>>>>> I don't know how difficult it would be. But it looks like a good >>>>>> precedent. >>>>> All you have to do is return "iio/..." from the devnode() callback. >>>> I admit I did not look closely into drivers/input/input.c before >>>> mentioning >>>> this >>>> as as good precedent. >>>> >>>> But, I looks like /dev/inpput is a class. >>>> While IIO devices are a bus_type devices. >>>> Should we start implementing an IIO class? or? >>> What I should have highlighted [before] with this, is that there is no >>> devnode() >>> callback for the bus_type [type]. >> But there is one in device_type :) > Many thanks :) > That worked nicely. > > I now have: > > root@analog:~# ls /dev/iio/* > /dev/iio/iio:device0 /dev/iio/iio:device1 > > /dev/iio/device3: > buffer0 buffer1 buffer2 buffer3 > > /dev/iio/device4: > buffer0 > > > It looks like I can shift these around as needed. > This is just an experiment. > I managed to move the iio devices under /dev/iio, though probably the IIO > devices will still be around as /dev/iio:deviceX for legacy reasons. > > Two things remain unresolved. > 1. The name of the IIO buffer device. > > root@analog:/sys/bus/iio/devices# ls iio\:device3/ > buffer in_voltage0_test_mode name > events in_voltage1_test_mode of_node > iio:buffer:3:0 in_voltage_sampling_frequency power > iio:buffer:3:1 in_voltage_scale scan_elements > iio:buffer:3:2 in_voltage_scale_available subsystem > iio:buffer:3:3 in_voltage_test_mode_available uevent > > > Right now, each buffer device is named 'iio:buffer:X:Y'. > One suggesttion was 'iio:deviceX:bufferY' > I'm suspecting the latter is preferred as when you sort the folders, buffers > come right after the iio:deviceX folders in /sys/bus/iio/devices. > > I don't feel it matters much the device name of the IIO buffer if we symlink it > to a shorter form. > > I'm guessing, we symlink these devices to short-hand 'bufferY' folders in each > 'iio:deviceX'?
I think that would be a bit excessive. Only for the legacy buffer we need to have a symlink.
> [...] > 2. I know this is [still] stupid now; but any suggestions one how to symlink > /dev/iio:device3 -> /dev/iio/device3/buffer0 ? > Does not seem to be possible. Userspace will have to take care of it. This means we need to keep legacy devices in /dev/ and only new buffers in /dev/iio/.
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