Using binary attributes for configuration sysfs entries

[Jay Aurabind]

On Wed, 13 Mar 2019 at 19:55, Greg KH <greg at kroah.com> wrote:
>
> On Wed, Mar 13, 2019 at 12:02:02PM +0530, Jay Aurabind wrote:
> > Hi,
> >
> > Before I send this patch to actual mailing list, I'd appreciate if
> > someone could tell me if this is a bad idea!
> >
> > The driver in staging for pi433 (a wireless transceiver) uses IOCTLs
> > at the moment. I wish to add a sysfs interface to it that control the
> > various transmission and reception parameters. In the ioctl interface,
> > it uses two structs that have about 40 parameters in total.
> >
> > For the corresponding sysfs interface, since there are a lot of
> > parameters, would it be justified to use the same binary format though
> > sysfs_create_binary_file() ? The rationale is that it would be easier
> > to simply pack all the config options in the struct and send it in
> > once rather than individually write 40 files. This is what the
> > attached patch follows. Interface is added only for reception
> > parameters as of now.
>
> binary sysfs files are only allowed for "pass through" data, where the
> kernel does not touch the information at all and only passes it from the
> hardware, to userspace directly (or the other way around).  It can not
> be used for data that the kernel actually knows about and modifies /
> acts on.
>
> An example of valid binary sysfs files are USB and PCI device
> configuration information (read directly from the hardware), or firmware
> files that are send from userspace directly to the hardware without the
> kernel knowing what the data is.
>
> You can't use a binary sysfs file for ioctl-like data, that's not
> allowed, just use an ioctl for that.  Or better yet, use a common api
> interface for it, to match the other types of devices.

Thank you for the explanation. What API would the most appropriate for
such a wireless transceiver ? If I could make it as a networking
driver, I could probably use setsockopt to pass in these
configuration. Is this recommended ?

>
> hope this helps,
>
> greg k-h


--

Thanks and Regards,
Jay