Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753930AbbG2REI (ORCPT ); Wed, 29 Jul 2015 13:04:08 -0400 Received: from xes-mad.com ([216.165.139.218]:33622 "EHLO xes-mad.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751164AbbG2REH (ORCPT ); Wed, 29 Jul 2015 13:04:07 -0400 Date: Wed, 29 Jul 2015 12:00:52 -0500 (CDT) From: Aaron Sierra To: Guenter Roeck Cc: Lee Jones , Matt Fleming , Wim Van Sebroeck , linux-kernel@vger.kernel.org, linux-watchdog@vger.kernel.org, Mika Westerberg , Andy Shevchenko , Jean Delvare , Wolfram Sang , Matt Fleming , Peter Tyser , Samuel Ortiz Message-ID: <1406016742.308627.1438189252821.JavaMail.zimbra@xes-inc.com> In-Reply-To: <55B90170.6080000@roeck-us.net> References: <1438004292-16382-1-git-send-email-matt@codeblueprint.co.uk> <20150728113721.GU14943@x1> <72454140.319490.1438109162683.JavaMail.zimbra@xes-inc.com> <20150729073841.GF2284@x1> <2115196252.256986.1438181571315.JavaMail.zimbra@xes-inc.com> <20150729153226.GB9319@x1> <1571539887.303369.1438186805578.JavaMail.zimbra@xes-inc.com> <55B90170.6080000@roeck-us.net> Subject: Re: [PATCH 1/5] iTCO_wdt: Expose watchdog properties using platform data MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-Originating-IP: [10.52.16.65] X-Mailer: Zimbra 8.0.6_GA_5922 (ZimbraWebClient - FF39 (Linux)/8.0.6_GA_5922) Thread-Topic: iTCO_wdt: Expose watchdog properties using platform data Thread-Index: djQRSR9aedsVz4v9fdwARkQp4oIz/Q== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4715 Lines: 118 ----- Original Message ----- > From: "Guenter Roeck" > Sent: Wednesday, July 29, 2015 11:38:08 AM > > On 07/29/2015 09:20 AM, Aaron Sierra wrote: > >> From: "Lee Jones" > >> Sent: Wednesday, July 29, 2015 10:32:26 AM > >> > >> On Wed, 29 Jul 2015, Aaron Sierra wrote: > >> > >>>> From: "Lee Jones" > >>>> Sent: Wednesday, July 29, 2015 2:38:41 AM > >>>> > >>>> On Tue, 28 Jul 2015, Aaron Sierra wrote: > >>>> > >>>>>>>>> @@ -933,7 +956,7 @@ gpe0_done: > >>>>>>>>> lpc_chipset_info[priv->chipset].use_gpio = ret; > >>>>>>>>> lpc_ich_enable_gpio_space(dev); > >>>>>>>>> > >>>>>>>>> - lpc_ich_finalize_cell(dev, &lpc_ich_cells[LPC_GPIO]); > >>>>>>>>> + lpc_ich_finalize_gpio_cell(dev); > >>>>>>>>> ret = mfd_add_devices(&dev->dev, PLATFORM_DEVID_AUTO, > >>>>>>>>> &lpc_ich_cells[LPC_GPIO], 1, NULL, 0, NULL); > >>>>>>>>> > >>>>>>>>> @@ -1007,7 +1030,10 @@ static int lpc_ich_init_wdt(struct > >>>>>>>>> pci_dev > >>>>>>>>> *dev) > >>>>>>>>> res->end = base_addr + ACPIBASE_PMC_END; > >>>>>>>>> } > >>>>>>>>> > >>>>>>>>> - lpc_ich_finalize_cell(dev, &lpc_ich_cells[LPC_WDT]); > >>>>>>>>> + ret = lpc_ich_finalize_wdt_cell(dev); > >>>>>>>>> + if (ret) > >>>>>>>>> + goto wdt_done; > >>>>>>>>> + > >>>>>>>>> ret = mfd_add_devices(&dev->dev, PLATFORM_DEVID_AUTO, > >>>>>>>>> &lpc_ich_cells[LPC_WDT], 1, NULL, 0, NULL); > >>>>>>>> > >>>>>>>> Why do you have an mfd_add_devices() call for each device? > >>>>>>> > >>>>>>> Good question. This call has been present since March 2012 when > >>>>>>> support > >>>>>>> was first added for iTCO_wdt in commit 887c8ec7219f ("watchdog: > >>>>>>> Convert > >>>>>>> iTCO_wdt driver to mfd model"). > >>>>>>> > >>>>>>> There's no good reason that I can see. Aaron? > >>>>> > >>>>> I chose to call mfd_add_devices() in each device init function > >>>>> because I thought it was the easiest way to avoid registering an > >>>>> incomplete/invalid MFD cell should an error occur during init. > >>>>> > >>>>> That way device registration wouldn't be an all-or-nothing affair. > >>>>> > >>>>> Doesn't mfd_add_devices() bail out after the first unsuccessful > >>>>> mfd to platform device translation? > >>>> > >>>> Right, as it should. > >>>> > >>>> Under what circumstance would an error occur and you'd wish to carry > >>>> on registering devices? > >>> > >>> Lee, > >>> > >>> The two devices that this driver is responsible for are conceptually > >>> independent; they simply are lumped together in one PCI device. No > >>> failure while preparing resources for the watchdog device should > >>> prevent the GPIO device from being registered. > >> > >> This makes me think that perhaps this isn't an MFD at all then? > >> > >> Perhaps I should invest some time to looking into that. > >> > >>> The most common real world circumstance that I experience is when a > >>> BIOS reserves resources associated with the GPIO device, thus > >>> preventing the GPIO resources (ICH_RES_GPE0 and/or ICH_RES_GPIO) from > >>> being fully prepared. > >>> > >>> I have not experienced issues with the watchdog device, but a similar > >>> issue would exist if the RCBA were disabled in a "v2" device. > >>> > >>> It seems like a dangerous change to simply attempt to register both > >>> of these devices with a single call, when one or both of them could > >>> be incomplete. > >>> > >>> Perhaps your real issue with this driver structure is that these > >>> cells are elements of a single lpc_ich_cells array for no clear > >>> reason. If each had a dedicated mfd_cell variable, would that be > >>> more acceptable to you? > >>> > >>> -static struct mfd_cell lpc_ich_cells[] = { > >>> +static struct mfd_cell lpc_ich_wdt_cell = { > >>> ... > >>> +static struct mfd_cell lpc_ich_gpio_cell = { > >>> > >>> That would eliminate the need for the lpc_cells enum, too. > >> > >> Yes, that would make more sense. Also consider using mfd_add_device() > >> instead of mfd_add_devices(), as you are only attempting registration > >> for a single device. > >> > > > > I can submit a patch the splits up the array elements, but I > > only see mfd_add_device() as a static function in mfd-core.c; > > Is that being exported in a development branch somewhere? > > > > Sure you want to do that ? You might have to move usage count > handling into the calling driver, and also provide mfd_remove_device(). Nope, just the array split-up! Thanks Guenter. -Aaron S. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/