On Thu, Sep 30, 2021 at 8:00 AM Alan Stern [off-list ref] wrote:

On Wed, Sep 29, 2021 at 06:55:12PM -0700, Dan Williams wrote:

quoted

On Wed, Sep 29, 2021 at 6:43 PM Alan Stern [off-list ref] wrote:

quoted

On Wed, Sep 29, 2021 at 06:05:06PM -0700, Kuppuswamy Sathyanarayanan wrote:

quoted

Currently bus drivers like "USB" or "Thunderbolt" implement a custom
version of device authorization to selectively authorize the driver
probes. Since there is a common requirement, move the "authorized"
attribute support to the driver core in order to allow it to be used
by other subsystems / buses.

Similar requirements have been discussed in the PCI [1] community for
PCI bus drivers as well.

No functional changes are intended. It just converts authorized
attribute from int to bool and moves it to the driver core. There
should be no user-visible change in the location or semantics of
attributes for USB devices.

Regarding thunderbolt driver, although it declares sw->authorized as
"int" and allows 0,1,2 as valid values for sw->authorized attribute,
but within the driver, in all authorized attribute related checks,
it is treated as bool value. So when converting the authorized
attribute from int to bool value, there should be no functional
changes other than value 2 being not visible to the user.

[1]: https://lore.kernel.org/all/CACK8Z6E8pjVeC934oFgr=VB3pULx_GyT2NkzAogdRQJ9TKSX9A@mail.gmail.com/ (local)

Reviewed-by: Dan Williams <redacted>
Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>

Since you're moving the authorized flag from the USB core to the
driver core, the corresponding sysfs attribute functions should be
moved as well.

Unlike when 'removable' moved from USB to the driver core there isn't
a common definition for how the 'authorized' sysfs-attribute behaves
across buses. The only common piece is where this flag is stored in
the data structure, i.e. the 'authorized' sysfs interface is
purposefully left bus specific.

How about implementing "library" versions of show_authorized() and
store_authorized() that the bus-specific attribute routines can call?
These library routines would handle parsing the input values, storing
the new flag, and displaying the stored flag value.  That way at
least the common parts of these APIs would be centralized in the
driver core, and any additional functionality could easily be added
by the bus-specific attribute routine.

While show_authorized() seems like it could be standardized, have a
look at what the different store_authorized() implementations do.
Thunderbolt wants "switch approval" vs "switch challenge" and USB has
a bunch of bus-specific work to do when the authorization state
changes. I don't see much room for a library to help there as more
buses add authorization support. That said I do think it would be
useful to have a common implementation available for generic probe
authorization to toggle the flag if the bus does not have any
authorization work to do, but that seems a follow-on once this core is
accepted.
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