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From: Thierry Reding <thierry.reding-RM9K5IK7kjKj5M59NBduVrNAH6kLmebB@public.gmane.org>
To: Russell King - ARM Linux <linux-lFZ/pmaqli7XmaaqVzeoHQ@public.gmane.org>
Cc: Lars-Peter Clausen <lars-Qo5EllUWu/uELgA04lAiVw@public.gmane.org>,
	linux-tegra-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	Mike Frysinger <vapier-aBrp7R+bbdUdnm+yROfE0A@public.gmane.org>,
	Arnd Bergmann <arnd-r2nGTMty4D4@public.gmane.org>,
	devicetree-discuss-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org,
	Mark Brown
	<broonie-yzvPICuk2AATkU/dhu1WVueM+bqZidxxQQ4Iyu8u01E@public.gmane.org>,
	Matthias Kaehlcke
	<matthias-RprLehDfhQ3k1uMJSBkQmQ@public.gmane.org>,
	Rob Herring <rob.herring-bsGFqQB8/DxBDgjK7y7TUQ@public.gmane.org>,
	Grant Likely
	<grant.likely-s3s/WqlpOiPyB63q8FvJNQ@public.gmane.org>,
	Olof Johansson <olof-nZhT3qVonbNeoWH0uzbU5w@public.gmane.org>,
	Richard Purdie <rpurdie-Fm38FmjxZ/leoWH0uzbU5w@public.gmane.org>,
	Colin Cross <ccross-z5hGa2qSFaRBDgjK7y7TUQ@public.gmane.org>,
	Mitch Bradley <wmb-D5eQfiDGL7eakBO8gow8eQ@public.gmane.org>,
	Eric Miao <eric.y.miao-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
	Sascha Hauer <s.hauer-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>,
	linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org,
	Kurt Van Dijck <kurt.van.dijck-/BeEPy95v10@public.gmane.org>
Subject: Re: [PATCH v2 02/10] pwm: Allow chips to support multiple PWMs.
Date: Wed, 8 Feb 2012 12:12:32 +0100	[thread overview]
Message-ID: <20120208111232.GB17615@avionic-0098.mockup.avionic-design.de> (raw)
In-Reply-To: <20120208091327.GH889-l+eeeJia6m9vn6HldHNs0ANdhmdF6hFW@public.gmane.org>

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* Russell King - ARM Linux wrote:
> On Tue, Feb 07, 2012 at 08:04:00AM +0100, Thierry Reding wrote:
> > One of the major problems when converting to a non-global namespace is how to
> > represent the relationship in code. For device tree this should be easy to do
> > because it has all the infrastructure in place. For non-device-tree devices I
> > have no idea yet how this could be done. Perhaps by using something like the
> > clock API and using names for lookup?
> 
> Well, the first step is to make sure that the pwm 'chip' drivers don't
> know anything about the global numberspace.
> 
> That limits the extent of the global numberspace to the pwm core and
> pwm users.  You then don't have to worry about the pwm chip drivers
> while you work out how to solve the other half of the problem.

I see. That would mean that pwm_request() gets a global PWM index, looks up
the corresponding PWM chip and device then pass the chip-relative index to
the driver's ops.

I think that can be simplified even further. For instance if the pwm_device
structure contains a pointer to its parent struct pwm_chip, then that can be
used directly to call into the driver's ops. And the ops could be modified to
take a pwm_device instead of the global PWM index. That would be similar to
how struct irq_data is used.

Thierry

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WARNING: multiple messages have this Message-ID (diff)
From: thierry.reding@avionic-design.de (Thierry Reding)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH v2 02/10] pwm: Allow chips to support multiple PWMs.
Date: Wed, 8 Feb 2012 12:12:32 +0100	[thread overview]
Message-ID: <20120208111232.GB17615@avionic-0098.mockup.avionic-design.de> (raw)
In-Reply-To: <20120208091327.GH889@n2100.arm.linux.org.uk>

* Russell King - ARM Linux wrote:
> On Tue, Feb 07, 2012 at 08:04:00AM +0100, Thierry Reding wrote:
> > One of the major problems when converting to a non-global namespace is how to
> > represent the relationship in code. For device tree this should be easy to do
> > because it has all the infrastructure in place. For non-device-tree devices I
> > have no idea yet how this could be done. Perhaps by using something like the
> > clock API and using names for lookup?
> 
> Well, the first step is to make sure that the pwm 'chip' drivers don't
> know anything about the global numberspace.
> 
> That limits the extent of the global numberspace to the pwm core and
> pwm users.  You then don't have to worry about the pwm chip drivers
> while you work out how to solve the other half of the problem.

I see. That would mean that pwm_request() gets a global PWM index, looks up
the corresponding PWM chip and device then pass the chip-relative index to
the driver's ops.

I think that can be simplified even further. For instance if the pwm_device
structure contains a pointer to its parent struct pwm_chip, then that can be
used directly to call into the driver's ops. And the ops could be modified to
take a pwm_device instead of the global PWM index. That would be similar to
how struct irq_data is used.

Thierry
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  parent reply	other threads:[~2012-02-08 11:12 UTC|newest]

Thread overview: 44+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-02-06 15:19 [PATCH v2 00/10] Add PWM framework and device-tree support Thierry Reding
2012-02-06 15:19 ` Thierry Reding
     [not found] ` <1328541585-24642-1-git-send-email-thierry.reding-RM9K5IK7kjKj5M59NBduVrNAH6kLmebB@public.gmane.org>
2012-02-06 15:19   ` [PATCH v2 01/10] PWM: add pwm framework support Thierry Reding
2012-02-06 15:19     ` Thierry Reding
2012-02-06 15:19   ` [PATCH v2 02/10] pwm: Allow chips to support multiple PWMs Thierry Reding
2012-02-06 15:19     ` Thierry Reding
     [not found]     ` <1328541585-24642-3-git-send-email-thierry.reding-RM9K5IK7kjKj5M59NBduVrNAH6kLmebB@public.gmane.org>
2012-02-06 21:22       ` Lars-Peter Clausen
2012-02-06 21:22         ` Lars-Peter Clausen
     [not found]         ` <4F3044A9.8000202-Qo5EllUWu/uELgA04lAiVw@public.gmane.org>
2012-02-07  7:04           ` Thierry Reding
2012-02-07  7:04             ` Thierry Reding
     [not found]             ` <20120207070400.GA29238-RM9K5IK7kjIQXX3q8xo1gnVAuStQJXxyR5q1nwbD4aMs9pC9oP6+/A@public.gmane.org>
2012-02-07 11:38               ` Mark Brown
2012-02-07 11:38                 ` Mark Brown
2012-02-08  9:13               ` Russell King - ARM Linux
2012-02-08  9:13                 ` Russell King - ARM Linux
     [not found]                 ` <20120208091327.GH889-l+eeeJia6m9vn6HldHNs0ANdhmdF6hFW@public.gmane.org>
2012-02-08 11:12                   ` Thierry Reding [this message]
2012-02-08 11:12                     ` Thierry Reding
2012-02-07 22:53       ` Ryan Mallon
2012-02-07 22:53         ` Ryan Mallon
     [not found]         ` <4F31AB63.3020301-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2012-02-08  8:15           ` Thierry Reding
2012-02-08  8:15             ` Thierry Reding
     [not found]             ` <20120208081508.GA6673-RM9K5IK7kjIQXX3q8xo1gnVAuStQJXxyR5q1nwbD4aMs9pC9oP6+/A@public.gmane.org>
2012-02-08  9:00               ` Sascha Hauer
2012-02-08  9:00                 ` Sascha Hauer
     [not found]                 ` <20120208090055.GP3852-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>
2012-02-08 11:16                   ` Thierry Reding
2012-02-08 11:16                     ` Thierry Reding
2012-02-08  9:17               ` Russell King - ARM Linux
2012-02-08  9:17                 ` Russell King - ARM Linux
     [not found]                 ` <20120208091720.GI889-l+eeeJia6m9vn6HldHNs0ANdhmdF6hFW@public.gmane.org>
2012-02-08 10:31                   ` Thierry Reding
2012-02-08 10:31                     ` Thierry Reding
2012-02-06 15:19   ` [PATCH v2 03/10] of: Add PWM support Thierry Reding
2012-02-06 15:19     ` Thierry Reding
2012-02-06 15:19   ` [PATCH v2 04/10] arm/tegra: Fix PWM clock programming Thierry Reding
2012-02-06 15:19     ` Thierry Reding
2012-02-06 15:19   ` [PATCH v2 05/10] arm/tegra: Provide clock for only one PWM controller Thierry Reding
2012-02-06 15:19     ` Thierry Reding
2012-02-06 15:19   ` [PATCH v2 06/10] pwm: Add NVIDIA Tegra SoC support Thierry Reding
2012-02-06 15:19     ` Thierry Reding
2012-02-06 15:19   ` [PATCH v2 07/10] arm/tegra: Add PWFM controller device tree probing Thierry Reding
2012-02-06 15:19     ` Thierry Reding
2012-02-06 15:19   ` [PATCH v2 08/10] pwm: Add Blackfin support Thierry Reding
2012-02-06 15:19     ` Thierry Reding
2012-02-06 15:19   ` [PATCH v2 09/10] pwm: Add PXA support Thierry Reding
2012-02-06 15:19     ` Thierry Reding
2012-02-06 15:19   ` [PATCH v2 10/10] pwm-backlight: Add rudimentary device tree support Thierry Reding
2012-02-06 15:19     ` Thierry Reding

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