On 2012-10-24 15:19, Ian Abbott wrote:
On 2012-10-24 05:16, Greg Kroah-Hartman wrote:
On Tue, Oct 23, 2012 at 10:53:22AM +0100, Ian Abbott wrote:
On 2012-10-22 20:44, Greg Kroah-Hartman wrote:
On Mon, Oct 15, 2012 at 01:07:30PM +0100, Ian Abbott wrote:
The auto-configuration/auto-attach mechanism in Comedi used by most of
the low-level PCI and USB Comedi hardware drivers currently uses
separate hooks in `struct comedi_driver` for each bus type -
`->attach_usb()` and `->attach_pci()`. I'd like to move away from that
and use a single auto-attach hook, `->auto_attach()` and make it easy
for an implementation of this hook in a low-level driver to get a
pointer to the `struct pci_dev`, `struct usb_interface` or whatever
device wrapper is relevant to the device being auto-attached to comedi.
Also, the Comedi core exports nice wrapper functions for auto-attaching
PCI or USB devices (`comedi_pci_auto_config()` and
`comedi_usb_auto_config()`) along with functions for auto-detaching
them, but there is currently no way to auto-attach devices on some
arbitrary type of bus. Export functions `comedi_auto_config()`
(different to the current static function of the same name) and
`comedi_auto_unconfig()`) to allow this.
Eventually, there will be nice wrapper functions for some more commonly
used device types such as PCMCIA, but it should be easy enough to
implement those as static inline wrappers around `comedi_auto_config()`
and `comedi_auto_unconfig()`.
This patch series only changes one PCI driver and one USB driver to use
the new `auto_attach()` hook, but it will be easy enough to change the
others. Once that is done, the `attach_pci()` and `attach_usb()` hooks
can be removed from `struct comedi_driver`.
I took the first two patches here only, care to rework the rest and
resend them?
I'm prepared to discuss the patches. One thing I want to allow is
for drivers to call comedi_auto_config() directly using whatever
context value they want (as long as it can be represented by an
unsigned long), and to have the same value passed back in their
auto_attach routine.
Ok, as long as nothing else outside that driver is trying to intrepret
that value as meaning anything.
Only the driver would interpret the context value, although most would
just ignore it. If the driver called comedi_auto_config() directly, it
would get the context back in its ->auto_config() hook. If the driver
used one of the wrappers around comedi_auto_config() such as
comedi_pci_auto_config(), it would get the predefined magic value as the
context "for free"; well, the context parameter would have to be set to
_something_ and some magic value that depends on which wrapper was
called is possibly more useful than a plain old 0 or NULL value.
Having comedi_pci_auto_config() pass a pointer to the `struct pci_dev`
in the context (and similar for other wrappers around
comedi_auto_config() handling different device types) wouldn't be
terribly useful to an ->auto_config() hook that could handle multiple
types of device wrappers as it wouldn't be able to tell what sort of
device type it should be dealing with as one random pointer value looks
pretty much like any other.
Okay, I'm just looking for a final decision before redoing the patches
(if necessary).
(1) Should drivers calling comedi_auto_config() directly be able to pass
a context value and have the same context value passed back via their
auto_attach() method?
(2) If 1, what is the most useful type for that context value?
(3) If 1, should pre-defined wrappers around comedi_auto_config() such
as comedi_pci_auto_config() and comedi_usb_auto_config() pass
pre-defined, "magic" values (which the driver will probably ignore) as
the context value in the driver's auto_attach() method or just pass some
"null" value?
--
-=( Ian Abbott @ MEV Ltd. E-mail: <abbotti@xxxxxxxxx> )=-
-=( Tel: +44 (0)161 477 1898 FAX: +44 (0)161 718 3587 )=-
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