Re: [Libusb-devel] HID Report Descriptor

[Greg KH <gr...@kr...>]

On Fri, Jan 21, 2011 at 10:39:15AM -0500, Alan Stern wrote:
> On Fri, 21 Jan 2011, Alan Ott wrote:
> 
> > > It would make more sense to export the report descriptors as binary
> > > blobs (rather than ASCII hex dumps), since that what they are.  And
> > > that's what programs expect to read.
> > >    
> > 
> > I agree. However, I thought there was a policy regarding sysfs about 
> > data being plain text? I thought I read that on LWN at one point. Maybe 
> > I'm wrong.
> 
> Yes, you're wrong.  See the usage of bin_attribute in fs/sysfs/bin.c.  
> For an example of a binary attribute, see the dev_bin_attr_descriptors
> stuff in drivers/usb/core/sysfs.c.

To be a bit more clear, binary attributes in sysfs are allowed, as long
as the kernel is only a "conduit" to the data, and it does not intrepret
it or modify it in any way.  For example, "raw" USB descriptor data, PCI
descriptor data, firmware files, etc, are all binary sysfs files.  HID
descriptor files would also be fine in sysfs as binary if the kernel
isn't trying to modify them in any manner.

thanks,

greg k-h