On Fri, Jan 15, 2021 at 04:26:21PM +0100, Alexander Potapenko wrote: > > sysfs is "one value per file" > What about existing interfaces that even export binary blobs through > sysfs (e.g. /sys/firmware, /sys/boot_params)? > What qualifies as a "value" in that case? binary files are fine as the kernel is just a "pipe" through to the hardware / firmware. No translation or parsing happens in the kernel. And that's NOT trace events :) > > please put something like this in > > tracefs, as there is no such rules there. Or debugfs, but please, not > > sysfs. > Does tracefs have anything similar to sysfs_notify() or any other way > to implement a poll() handler? Don't know, look and see! > Our main goal is to let users wait on poll(), so that they don't have > to check the file for new contents every now and then. Is it possible > with tracefs or debugfs? debugfs, yes, you can do whatever you want. tracefs probably has this, otherwise how would trace tools work? :) > Also, for our goal debugfs isn't a particularly good fit, as Android > kernels do not enable debugfs. Do you care about Android kernels? If so, yes, debugfs is not good. And have you asked the Android kernel team about this? > Not sure about tracefs, they seem to have it, need to check. It should be there. > Do you think it is viable to keep > /sys/kernel/error_report/report_count in sysfs and use it for > notifications, but move last_report somewhere else? No, not at all, please keep it out of sysfs. > (I'd probably prefer procfs, but it could be tracefs as well, if you > find that better). If it does not have to do with processes, it does not belong in procfs. Again, this seems to fit in with tracing, so please use tracefs. > This way it will still be possible to easily notify userspace about > new reports, but the report itself won't have any atomicity > guarantees. Users will have to check the report count to ensure it > didn't change under their feet. Again, use a file in tracefs. thanks, greg k-h
