Re: [PATCH 2/2] staging: comedi: addi_apci_1564: use addi_watchdog module to init watchdog subdevice

From: Ian Abbott
Date: Tue Jul 15 2014 - 06:15:30 EST

On 2014-07-15 05:00, Chase Southwood wrote:
On Mon, Jul 14, 2014 at 4:22 AM, Ian Abbott <abbotti@xxxxxxxxx> wrote:
On 2014-07-12 23:44, Chase Southwood wrote:

Use the addi_watchdog module to provide support for the watchdog

Also, rearrange the subdevice init blocks so that the order makes sense.
Digital input/output subdevices and subdevices for DI/DO interrupt
support, followed by timer/counter/watchdog subdevices is the new order.

Signed-off-by: Chase Southwood <chase.southwood@xxxxxxxxx>
Cc: Ian Abbott <abbotti@xxxxxxxxx>
Cc: H Hartley Sweeten <hsweeten@xxxxxxxxxxxxxxxxxxx>
drivers/staging/comedi/drivers/addi_apci_1564.c | 34
1 file changed, 20 insertions(+), 14 deletions(-)

I don't think the subdevice order matters that much, and I prefer to keep
them stable, but since this driver is in such a state of flux, it doesn't
really matter.

Hi Ian!
Quick question here about this. First off, duly noted that grouping
subdevices by function isn't necessary and I won't shuffle them around
like this in the future. Second, the reason I stuck the watchdog at
the end is because it causes an early return if addi_watchdog_init()
returns an error and it seemed appropriate at the end so it doesn't
prevent the initialization of any other subdevices if that call should
fail. Now I realize that it is very unlikely that that call fails,
but in any case should I put future subdevice inits above the watchdog
for the same reason (so they aren't at risk of not getting
initialized), or does that count for subdevice order not being stable
and you would prefer them all to go at the end?

Since you return an error from the auto_attach handler apci1564_auto_attach() when addi_watchdog_init() fails, it makes little difference what order the subdevices are initialized in. The error from auto_attach handler causes the comedi core to call the detach handler apci1564_detach() and tear everything down. Ultimately, comedi_pci_auto_attach() will return an error back to the PCI probe function apci1564_pci_probe(), which will propagate it to the PCI subsystem.

In general, if adding a new subdevice, either add it to the end or replace an "unused" subdevice.

-=( Ian Abbott @ MEV Ltd. E-mail: <abbotti@xxxxxxxxx> )=-
-=( Tel: +44 (0)161 477 1898 FAX: +44 (0)161 718 3587 )=-
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