linux-kernel - Re: [PATCH] driver/i2c/mux: Add register based mux i2c-mux-reg

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Message-ID: <55827A1E.4020608@nokia.com>
Date:	Thu, 18 Jun 2015 09:58:22 +0200
From:	Alexander Sverdlin <alexander.sverdlin@...ia.com>
To:	ext York Sun <yorksun@...escale.com>, wsa@...-dreams.de
Cc:	linux-kernel@...r.kernel.org, linux-i2c@...r.kernel.org,
	Peter Korsgaard <peter.korsgaard@...co.com>
Subject: Re: [PATCH] driver/i2c/mux: Add register based mux i2c-mux-reg

Hello!

On 17/06/15 18:43, ext York Sun wrote:
>> > Yeah, this is really bad idea. You maybe want something like
>> > __iomem "cookie" here instead of this bare pointer.
> Let me try.
> 

Could you think about different access widths, please?
Not all buses are 32-bits wide and even on 64-bit CPUs one might have 16-bit bus
and 32 bits accesses are not allowed or perform two accesses, etc...

So to cover the use-cases which I see one needs to have a possibility to select between
__raw_writeb()/__raw_writew()/__raw_writel()/__raw_writeq() (now that I'm thinking about
it, I think these native-Endianness functions are preferred and if one has a bus with
different Endianness he should think about the conversion in the reg property of subnodes).

Very important is readback with corresponding __raw_read*(), but maybe you want to do
this optional via additional DT property...

-- 
Best regards,
Alexander Sverdlin.
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