On Tue, Sep 26, 2017 at 05:50:55PM +0200, Federico Vaga wrote: > Hello, > > I'm writing a sysfs binary attribute that makes use of the `mmap` operation.
Eeek, why? What are you using that for? sysfs binary attributes are for dumping binary data that the kernel doesn't touch/parse, through to hardware. Why use mmap for this? Do you have a pointer to your code somewhere? > I would like to implement my own `open()` and `close()` `vm_ops` but > apparently I'm not allowed to do it. Nope, you are not, not in sysfs :) > > -------- kernfs/file.c - kernfs_fop_mmap () - modern kernel ----- > -------- sysfs/bin.c - mmap () - old kernel ----- > > /* > * It is not possible to successfully wrap close. > * So error if someone is trying to use close. > */ > rc = -EINVAL; > if (vma->vm_ops && vma->vm_ops->close) > goto out_put; > ---------------------------------------------------------- > > What is the reason behind this choice? > Why "it is not possible to successfully wrap close" ? Because you shouldn't be doing that :) > Is there an alternative/hack in order to be notified when the mmap is not > used > anymore and I can properly release my resources? Don't use mmap in sysfs :) > Due to HW resources limitation I "cannot" keep the device memory mapped when > nobody is using it, that's why I would like to be able to use > vm_ops->close(). > In general, I would like to run my routine that release resources when the > user does `munmap` or `close` Don't use mmap in sysfs :) What problem are you trying to solve here that mmap seemed like the correct solution? thanks, greg k-h
