From: Thierry Reding <firstname.lastname@example.org> To: Lee Jones <email@example.com> Cc: Rob Herring <firstname.lastname@example.org>, email@example.com, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, email@example.com Subject: Re: [PATCH v3 20/20] dt-bindings: pwm: sti: Update DT bindings with recent changes Date: Fri, 10 Jun 2016 15:18:55 +0200 [thread overview] Message-ID: <20160610131855.GG27142@ulmo.ba.sec> (raw) In-Reply-To: <20160609114107.GB1388@dell> [-- Attachment #1: Type: text/plain, Size: 2821 bytes --] On Thu, Jun 09, 2016 at 12:41:07PM +0100, Lee Jones wrote: > On Wed, 08 Jun 2016, Rob Herring wrote: > > > On Wed, Jun 08, 2016 at 10:21:35AM +0100, Lee Jones wrote: > > > We're renaming the 'st,pwm-num-chan' binding to 'st,pwm-num-devs' to > > > be more inline with the naming conventions of the subsystem. Where > > > we used to treat each line as a channel, the PWM convention is to > > > describe them as devices. > > > > That's all linux implementation details and you are breaking > > compatibility. > > Normally I'd agree with you, but I happen to know that a) this IP is > currently unused and b) up until this point (and probably beyond), ST > always ship the DTB with the kernel, so there will be no breakage. Heh... I've long given up on trying to make that argument go anywhere. The general rule is that once we support a binding in a kernel release we have to support it indefinitely. If you really want to go ahead with this change (I don't think you should), you'd at least have to document both properties and support st,pwm-num-chan in the driver for backwards compatibility. > > > The second documentation adaption entails adding support for PWM > > > capture devices. A new clock is required as well as an IRQ line. > > > We're also adding a new property similar to the one described > > > above, but for capture channels. Typically, there will be less > > > capture channels than PWM-out, since all channels have the latter > > > capability, but only some have capture support. > > > > Humm, sounds like all of this should be implied from compatible strings. > > You mean have a bunch of of_machine_is_compatibles() scattered around? I don't understand why you need this at all. Quite frankly I don't even know why st,pwm-num-devs exists. I probably missed it back at the time. Usually, like Rob suggests, this should be inferred from the compatible string. One commonly used way to avoid scattering explicit checks for the compatible string is to add this information to the of_device_id table. See a bunch of existing drivers for reference. Also, why make a separation of output vs. capture channels at this point? Could you not simply obtain the total number of PWM channels, preferably from SoC data associated with the compatible string, and check at ->capture() time whether or not the particular PWM supports this? As-is, you imply that you have n (output) + m (capture) channels, and that 0..n-1 are output and n..n+m-1 are capture channels. What if that no longer holds true, but 0 and 2 are the only ones that support capture? If you check for this at runtime you can avoid complicated DT parsing code, but still get the safety check which should be enough to encourage people to use the right channels in DT. Thierry [-- Attachment #2: signature.asc --] [-- Type: application/pgp-signature, Size: 819 bytes --]
next prev parent reply other threads:[~2016-06-10 13:19 UTC|newest] Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top 2016-06-08 9:21 [PATCH v3 00/20] pwm: Add support for PWM Capture Lee Jones 2016-06-08 9:21 ` [PATCH v3 01/20] ARM: dts: STi: Rename properites in line with PWM naming conventions Lee Jones 2016-06-08 9:21 ` [PATCH v3 02/20] ARM: dts: STiH407: Supply PWM Capture IRQ Lee Jones 2016-06-08 9:21 ` [PATCH v3 03/20] ARM: dts: STiH407: Declare PWM Capture data lines via Pinctrl Lee Jones 2016-06-08 9:21 ` [PATCH v3 04/20] ARM: dts: STiH416: Supply PWM Capture IRQs Lee Jones 2016-06-08 9:21 ` [PATCH v3 05/20] ARM: dts: STiH416: Declare PWM Capture data lines via Pinctrl Lee Jones 2016-06-08 9:21 ` [PATCH v3 06/20] ARM: dts: STiH416: Define PWM Capture clock Lee Jones 2016-06-08 9:21 ` [PATCH v3 07/20] ARM: dts: STiH416: Define the number of PWM Capture channels Lee Jones 2016-06-08 9:21 ` [PATCH v3 08/20] pwm: Add PWM Capture support Lee Jones 2016-06-10 13:53 ` Thierry Reding 2016-06-10 14:38 ` Lee Jones 2016-06-10 16:39 ` Thierry Reding 2016-06-20 11:14 ` Lee Jones 2016-06-08 9:21 ` [PATCH v3 09/20] pwm: sti: Rename channel => device Lee Jones 2016-06-08 9:21 ` [PATCH v3 10/20] pwm: sysfs: Add PWM Capture support Lee Jones 2016-06-10 14:04 ` Thierry Reding 2016-06-10 14:36 ` Lee Jones 2016-06-08 9:21 ` [PATCH v3 11/20] pwm: sti: Reorganise register names in preparation for new functionality Lee Jones 2016-06-08 9:21 ` [PATCH v3 12/20] pwm: sti: Only request clock rate when you need to Lee Jones 2016-06-08 9:21 ` [PATCH v3 13/20] pwm: sti: Supply PWM Capture register addresses and bit locations Lee Jones 2016-06-08 9:21 ` [PATCH v3 14/20] pwm: sti: Supply PWM Capture clock handling Lee Jones 2016-06-08 9:21 ` [PATCH v3 15/20] pwm: sti: Initialise PWM Capture device data Lee Jones 2016-06-08 9:21 ` [PATCH v3 16/20] pwm: sti: Add support for PWM Capture IRQs Lee Jones 2016-06-08 9:21 ` [PATCH v3 17/20] pwm: sti: Add PWM Capture call-back Lee Jones 2016-06-08 9:21 ` [PATCH v3 18/20] pwm: sti: It's now valid for number of PWM channels to be zero Lee Jones 2016-06-08 9:21 ` [PATCH v3 19/20] pwm: sti: Take the opportunity to conduct a little house keeping Lee Jones 2016-06-08 9:21 ` [PATCH v3 20/20] dt-bindings: pwm: sti: Update DT bindings with recent changes Lee Jones 2016-06-08 20:51 ` Rob Herring 2016-06-09 11:41 ` Lee Jones 2016-06-10 13:18 ` Thierry Reding [this message] 2016-06-10 14:06 ` Lee Jones 2016-06-10 14:53 ` Thierry Reding 2016-06-10 15:19 ` Lee Jones 2016-07-13 9:02 ` Lee Jones 2016-06-10 13:10 ` Thierry Reding
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