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From: Wolfram Sang <wsa@the-dreams.de>
To: Laine Jaakko EXT <ext-jaakko.laine@vaisala.com>
Cc: "michal.simek@xilinx.com" <michal.simek@xilinx.com>,
	Shubhrajyoti Datta <shubhrajyoti.datta@gmail.com>,
	"linux-arm-kernel@lists.infradead.org"
	<linux-arm-kernel@lists.infradead.org>,
	"linux-i2c@vger.kernel.org" <linux-i2c@vger.kernel.org>
Subject: Re: [PATCH] i2c: xiic: Support disabling multi-master in DT
Date: Wed, 1 Apr 2020 16:41:59 +0200	[thread overview]
Message-ID: <20200401143254.GA2409@ninjato> (raw)
In-Reply-To: <AM0PR06MB5185E501349E06428093B62FD4F70@AM0PR06MB5185.eurprd06.prod.outlook.com>


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> The multi-master -binding is documented here as boolean and encodes a
> Boolean by either existing or not existing in device tree. It is also
> used in other drivers so I couldn't do much about it missing meaning
> False.
> https://github.com/torvalds/linux/blob/master/Documentation/devicetree/bindings/i2c/i2c.txt
> I originally had a custom device tree entry where the default was for
> multi-master to be enabled before I noticed the pre-existing binding.
> 
> Maybe if the multi-master binding was changed from Boolean to for
> example a string property (multi-master = "ON" / multi-master =
> "OFF"), code could still just check the existence with
> "of_property_read_bool()" first, where property missing means "OFF"
> and property existing means "ON"(like before) if there is no text
> associated. Xiic driver would then only disable multimaster, if device
> tree explicitly contains multi-master = "OFF".
> 
> This should be able to maintain driver backwards compatibility with
> old device trees, but requires binding documentation change and all
> drivers should likely be updated to also accept the new style of
> multi-master property to be consistent. This is also not as clean as
> the old Boolean property in my opinion.

I agree. I don't want to change the old "multi-master" binding like
above because that would be quite intrusive for other drivers and
confusing when trying to understand the binding.

My best bet is to introduce another binding "single-master" which says
clearly that we are the only bus master on that bus.

Both bindings missing means then "unclear".

I think this matches reality best.

Opinions?


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  parent reply	other threads:[~2020-04-01 14:42 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-18 13:58 [PATCH] i2c: xiic: Support disabling multi-master in DT Laine Jaakko EXT
2020-02-24 10:13 ` Michal Simek
2020-02-25 14:08   ` Laine Jaakko EXT
2020-02-25 14:13     ` Wolfram Sang
2020-02-25 14:27       ` Laine Jaakko EXT
2020-02-25 14:32         ` Wolfram Sang
2020-02-25 14:37           ` Michal Simek
2020-02-25 14:41             ` Wolfram Sang
2020-02-25 14:44               ` Michal Simek
2020-02-25 14:48                 ` Wolfram Sang
2020-02-25 14:49                   ` Michal Simek
2020-03-18 12:20 ` Shubhrajyoti Datta
2020-03-18 16:49   ` Laine Jaakko EXT
2020-03-19  9:34     ` Shubhrajyoti Datta
2020-03-19 10:26       ` Laine Jaakko EXT
2020-04-16 10:42         ` Laine Jaakko EXT
2020-04-01 14:41     ` Wolfram Sang [this message]
2020-04-02  6:16       ` Laine Jaakko EXT
2020-04-02  9:28         ` Wolfram Sang
2020-05-04 12:58           ` Laine Jaakko EXT
2020-05-27 11:07             ` Wolfram Sang
2020-05-27 11:27               ` Laine Jaakko EXT

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