Re: [PATCH 1/3] USB: core: Add routines for endpoint checks in old drivers

[Alan Stern <stern@rowland.harvard.edu>]

On Wed, Apr 12, 2023 at 01:54:12PM +0200, Oliver Neukum wrote:
> On 10.04.23 21:37, Alan Stern wrote:
> 
> Hi,
> > To make this checking as simple as possible, we now add a couple of
> > utility routines to the USB core.  usb_check_bulk_endpoints() and
> > usb_check_int_endpoints() take an interface pointer together with a
> > list of endpoint addresses (numbers and directions).  They check that
> > the interface's current alternate setting includes endpoints with
> > those addresses and that each of these endpoints has the right type:
> > bulk or interrupt, respectively.
> > 
> > Although we already have usb_find_common_endpoints() and related
> > routines meant for a similar purpose, they are not well suited for
> > this kind of checking.  Those routines find endpoints of various
> > kinds, but only one (either the first or the last) of each kind, and
> > they don't verify that the endpoints' addresses agree with what the
> > caller expects.
> 
> these will do the job. Yet this strikes me as unelegant. That is
> if you define a data structure to match against, why not
> add a pointer to it to struct usb_device_id and use that?

Struct usb_device_id doesn't seem like the right place.  Struct 
usb_driver would be more appropriate.  The drivers that need this have 
only one entry in their match table, which means that drivers with large 
match tables (which would require a lot of extra space for the new 
pointers) don't need it.

> Basically the table of endpoints you are creating is a description of
> a device. Why add code for checking it to each probe() method
> that needs it?

True, the checks could be centralized in usb_probe_interface().  What do 
you think about doing it that way?

Alan Stern