From: Mark Brown <broonie-yzvPICuk2AATkU/dhu1WVueM+bqZidxxQQ4Iyu8u01E@public.gmane.org> To: Grant Likely <grant.likely-s3s/WqlpOiPyB63q8FvJNQ@public.gmane.org> Cc: "davinci-linux-open-source-VycZQUHpC/PFrsHnngEfi1aTQe2KTcn/@public.gmane.org" <davinci-linux-open-source-VycZQUHpC/PFrsHnngEfi1aTQe2KTcn/@public.gmane.org>, "dbrownell-Rn4VEauK+AKRv+LV9MX5uipxlwaOVQ5f@public.gmane.org" <dbrownell-Rn4VEauK+AKRv+LV9MX5uipxlwaOVQ5f@public.gmane.org>, "sameo-VuQAYsv1563Yd54FQh9/CA@public.gmane.org" <sameo-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>, "khilman-1D3HCaltpLuhEniVeURVKkEOCMrvLtNR@public.gmane.org" <khilman-1D3HCaltpLuhEniVeURVKkEOCMrvLtNR@public.gmane.org>, Greg Kroah-Hartman <gregkh-l3A5Bk7waGM@public.gmane.org>, "Rafael J. Wysocki" <rjw-KKrjLPT3xs0@public.gmane.org>, "rpurdie-Fm38FmjxZ/leoWH0uzbU5w@public.gmane.org" <rpurdie-Fm38FmjxZ/leoWH0uzbU5w@public.gmane.org>, "linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org" <linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org>, Cyril Chemparathy <cyril-l0cyMroinI0@public.gmane.org>, "spi-devel-general-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org" <spi-devel-general-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org>, "akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org" <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>, "alan-qBU/x9rampVanCEyBjwyrvXRex20P6io@public.gmane.org" <alan-qBU/x9rampVanCEyBjwyrvXRex20P6io@public.gmane.org>, "lrg-kDsPt+C1G03kYMGBc/C6ZA@public.gmane.org" <lrg-kDsPt+C1G03kYMGBc/C6ZA@public.gmane.org> Subject: Re: [PATCH v5 04/12] spi: add ti-ssp spi master driver Date: Wed, 17 Nov 2010 17:23:58 +0000 [thread overview] Message-ID: <20101117172357.GC19488@rakim.wolfsonmicro.main> (raw) In-Reply-To: <20101117161130.GC5757-MrY2KI0G/OVr83L8+7iqerDks+cytr/Z@public.gmane.org> On Wed, Nov 17, 2010 at 09:11:30AM -0700, Grant Likely wrote: > To start, I'm not a fan of matching by name. It's fragile because it > makes assumptions about how devices will be names when they actually > appear (ie. Sometimes .id is dynamically assigned). Ideally I'd > prefer to have direct references (ie. pointers) to the devices that > need to be registered, which *shouldn't* be difficult to handle. That Pointers are a complete pain for buses where things are dynamically instantiated, the things you have to point at in machine data aren't the things that end up appearing during device registration when the struct device gets dynamically allocated so you need some way of translating them. This is why everyone ends up using dev_name for this sort of thing ATM, it's easy to put into the code and match against the actual struct device at runtime without needing to know about bus types. > guarantees that the correct device is always referenced. (aside: the > device-tree use case provides this information by having direct > 'phandle' references between dependencies.) Device tree makes this a lot easier. > Option 1: Add a list of prerequisite devices to struct device and > modify driver core so that it defers binding to a driver until all the > prerequisites are already bound. This can probably be implemented > in a way that works for all bus types transparently. Before binding > a driver, the driver core would increase the ref count on each of the > prereq devices, and decrease it again when the driver is removed. > Option 2: On a per-bus_type basis have a separate registration and the > bus type code would hold the device unregistered in a pending list. > This option would also add a prerequisites list to struct device. Per bus type sounds like a lot of hassle going through all the bus types but we may need to do that to handle autoprobable buses like USB. I do like the idea that the core would know what's going on so that things do become visible for the debuggabilty reasons you mention, though helpers could also provide similar infrastructure. > Option 3: Don't try to handle it in the bus_type or driver core code > at all, but rather provide board support code with helpers to make > waiting for other devices easy. Even in this case I think it is > probably still a good idea for the dependant devices to increment > the refcount of the prereq devices. Agreed on the refcounting. ------------------------------------------------------------------------------ Beautiful is writing same markup. Internet Explorer 9 supports standards for HTML5, CSS3, SVG 1.1, ECMAScript5, and DOM L2 & L3. Spend less time writing and rewriting code and more time creating great experiences on the web. Be a part of the beta today http://p.sf.net/sfu/msIE9-sfdev2dev
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From: broonie@opensource.wolfsonmicro.com (Mark Brown) To: linux-arm-kernel@lists.infradead.org Subject: [PATCH v5 04/12] spi: add ti-ssp spi master driver Date: Wed, 17 Nov 2010 17:23:58 +0000 [thread overview] Message-ID: <20101117172357.GC19488@rakim.wolfsonmicro.main> (raw) In-Reply-To: <20101117161130.GC5757@angua.secretlab.ca> On Wed, Nov 17, 2010 at 09:11:30AM -0700, Grant Likely wrote: > To start, I'm not a fan of matching by name. It's fragile because it > makes assumptions about how devices will be names when they actually > appear (ie. Sometimes .id is dynamically assigned). Ideally I'd > prefer to have direct references (ie. pointers) to the devices that > need to be registered, which *shouldn't* be difficult to handle. That Pointers are a complete pain for buses where things are dynamically instantiated, the things you have to point at in machine data aren't the things that end up appearing during device registration when the struct device gets dynamically allocated so you need some way of translating them. This is why everyone ends up using dev_name for this sort of thing ATM, it's easy to put into the code and match against the actual struct device at runtime without needing to know about bus types. > guarantees that the correct device is always referenced. (aside: the > device-tree use case provides this information by having direct > 'phandle' references between dependencies.) Device tree makes this a lot easier. > Option 1: Add a list of prerequisite devices to struct device and > modify driver core so that it defers binding to a driver until all the > prerequisites are already bound. This can probably be implemented > in a way that works for all bus types transparently. Before binding > a driver, the driver core would increase the ref count on each of the > prereq devices, and decrease it again when the driver is removed. > Option 2: On a per-bus_type basis have a separate registration and the > bus type code would hold the device unregistered in a pending list. > This option would also add a prerequisites list to struct device. Per bus type sounds like a lot of hassle going through all the bus types but we may need to do that to handle autoprobable buses like USB. I do like the idea that the core would know what's going on so that things do become visible for the debuggabilty reasons you mention, though helpers could also provide similar infrastructure. > Option 3: Don't try to handle it in the bus_type or driver core code > at all, but rather provide board support code with helpers to make > waiting for other devices easy. Even in this case I think it is > probably still a good idea for the dependant devices to increment > the refcount of the prereq devices. Agreed on the refcounting.
next prev parent reply other threads:[~2010-11-17 17:23 UTC|newest] Thread overview: 74+ messages / expand[flat|nested] mbox.gz Atom feed top 2010-11-15 19:12 [PATCH v5 00/12] tnetv107x ssp drivers Cyril Chemparathy 2010-11-15 19:12 ` Cyril Chemparathy [not found] ` <1289848334-8695-1-git-send-email-cyril-l0cyMroinI0@public.gmane.org> 2010-11-15 19:12 ` [PATCH v5 01/12] misc: add driver for sequencer serial port Cyril Chemparathy 2010-11-15 19:12 ` Cyril Chemparathy [not found] ` <1289848334-8695-2-git-send-email-cyril-l0cyMroinI0@public.gmane.org> 2010-11-16 7:10 ` Grant Likely 2010-11-16 7:10 ` Grant Likely [not found] ` <20101116071047.GE4074-MrY2KI0G/OVr83L8+7iqerDks+cytr/Z@public.gmane.org> 2010-11-16 16:15 ` Cyril Chemparathy 2010-11-16 16:15 ` Cyril Chemparathy [not found] ` <4CE2AE3C.4040805-l0cyMroinI0@public.gmane.org> 2010-11-16 20:35 ` Grant Likely 2010-11-16 20:35 ` Grant Likely [not found] ` <AANLkTik76EY8Xh01YP2Tep6k1ETPO+3idmNuk3pVikJG-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> 2010-11-16 21:19 ` Cyril Chemparathy 2010-11-16 21:19 ` Cyril Chemparathy 2010-11-16 22:23 ` Russell King - ARM Linux 2010-11-16 22:23 ` Russell King - ARM Linux [not found] ` <20101116222340.GF21926-l+eeeJia6m9vn6HldHNs0ANdhmdF6hFW@public.gmane.org> 2010-11-16 23:57 ` Grant Likely 2010-11-16 23:57 ` Grant Likely 2010-11-15 19:12 ` [PATCH v5 02/12] davinci: add tnetv107x ssp platform device Cyril Chemparathy 2010-11-15 19:12 ` Cyril Chemparathy 2010-11-15 19:12 ` [PATCH v5 03/12] davinci: add ssp config for tnetv107x evm board Cyril Chemparathy 2010-11-15 19:12 ` Cyril Chemparathy 2010-11-15 19:12 ` [PATCH v5 04/12] spi: add ti-ssp spi master driver Cyril Chemparathy 2010-11-15 19:12 ` Cyril Chemparathy 2010-11-15 21:59 ` Ryan Mallon 2010-11-15 21:59 ` Ryan Mallon [not found] ` <1289848334-8695-5-git-send-email-cyril-l0cyMroinI0@public.gmane.org> 2010-11-16 7:22 ` Grant Likely 2010-11-16 7:22 ` Grant Likely [not found] ` <20101116072225.GF4074-MrY2KI0G/OVr83L8+7iqerDks+cytr/Z@public.gmane.org> 2010-11-16 7:47 ` Grant Likely 2010-11-16 7:47 ` Grant Likely 2010-11-16 11:34 ` Mark Brown 2010-11-16 11:34 ` Mark Brown [not found] ` <20101116113409.GH3338-GFdadSzt00ze9xe1eoZjHA@public.gmane.org> 2010-11-16 20:45 ` Grant Likely 2010-11-16 20:45 ` Grant Likely [not found] ` <20101116204554.GB5016-MrY2KI0G/OVr83L8+7iqerDks+cytr/Z@public.gmane.org> 2010-11-16 22:48 ` Mark Brown 2010-11-16 22:48 ` Mark Brown [not found] ` <AANLkTi=utWumLKo9QVWXpkC8WxpgaNJJs+dj=pa2eq-q-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> 2010-11-17 0:17 ` Cyril Chemparathy 2010-11-17 0:17 ` Cyril Chemparathy 2010-11-17 13:31 ` Mark Brown 2010-11-17 13:31 ` Mark Brown [not found] ` <20101117133136.GA19488-HF5t3jzXg/6ND3a5+9QAFujbO/Zr0HzV@public.gmane.org> 2010-11-17 15:25 ` David Brownell 2010-11-17 15:25 ` David Brownell [not found] ` <781931.83221.qm-g47maUHHHF+ORdMXk8NaZPu2YVrzzGjVVpNB7YpNyf8@public.gmane.org> 2010-11-17 17:54 ` Cyril Chemparathy 2010-11-17 17:54 ` Cyril Chemparathy [not found] ` <4CE31F0E.7050103-l0cyMroinI0@public.gmane.org> 2010-11-17 16:11 ` Grant Likely 2010-11-17 16:11 ` Grant Likely [not found] ` <20101117161130.GC5757-MrY2KI0G/OVr83L8+7iqerDks+cytr/Z@public.gmane.org> 2010-11-17 17:23 ` Mark Brown [this message] 2010-11-17 17:23 ` Mark Brown 2010-11-17 17:35 ` Cyril Chemparathy 2010-11-17 17:35 ` Cyril Chemparathy 2010-11-18 5:46 ` Greg KH 2010-11-18 5:46 ` Greg KH 2010-11-25 23:32 ` Rafael J. Wysocki 2010-11-25 23:32 ` Rafael J. Wysocki 2010-11-16 14:19 ` David Brownell 2010-11-16 14:19 ` David Brownell 2010-11-15 19:12 ` [PATCH v5 05/12] davinci: add spi devices on tnetv107x evm Cyril Chemparathy 2010-11-15 19:12 ` Cyril Chemparathy 2010-11-15 19:12 ` [PATCH v5 06/12] regulator: add driver for tps6524x regulator Cyril Chemparathy 2010-11-15 19:12 ` Cyril Chemparathy 2010-11-15 19:12 ` [PATCH v5 07/12] davinci: add tnetv107x evm regulators Cyril Chemparathy 2010-11-15 19:12 ` Cyril Chemparathy 2010-11-15 19:12 ` [PATCH v5 08/12] gpio: add ti-ssp gpio driver Cyril Chemparathy 2010-11-15 19:12 ` Cyril Chemparathy [not found] ` <1289848334-8695-9-git-send-email-cyril-l0cyMroinI0@public.gmane.org> 2010-11-15 22:38 ` Ryan Mallon 2010-11-15 22:38 ` Ryan Mallon [not found] ` <4CE1B651.1060006-7Wk5F4Od5/oYd5yxfr4S2w@public.gmane.org> 2010-11-16 19:38 ` Cyril Chemparathy 2010-11-16 19:38 ` Cyril Chemparathy 2010-11-15 19:12 ` [PATCH v5 09/12] davinci: add tnetv107x evm ti-ssp gpio device Cyril Chemparathy 2010-11-15 19:12 ` Cyril Chemparathy 2010-11-15 19:12 ` [PATCH v5 10/12] backlight: add support for tps6116x controller Cyril Chemparathy 2010-11-15 19:12 ` Cyril Chemparathy 2010-11-15 19:12 ` [PATCH v5 11/12] davinci: add tnetv107x evm backlight device Cyril Chemparathy 2010-11-15 19:12 ` Cyril Chemparathy 2010-11-15 19:12 ` [PATCH v5 12/12] davinci: add tnetv107x evm i2c eeprom device Cyril Chemparathy 2010-11-15 19:12 ` Cyril Chemparathy
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