linux-kernel - Re: [PATCH v4 6/8] media: imx274: add helper function to fill a reg

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Date:   Wed, 27 Jun 2018 10:13:12 +0200
From:   Luca Ceresoli <luca@...aceresoli.net>
To:     Sakari Ailus <sakari.ailus@....fi>
Cc:     linux-media@...r.kernel.org,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Leon Luo <leonl@...pardimaging.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 6/8] media: imx274: add helper function to fill a reg_8
 table chunk

Hi Sakari,

On 26/06/2018 14:20, Sakari Ailus wrote:
> Hi Luca,
> 
> On Mon, Jun 11, 2018 at 01:35:37PM +0200, Luca Ceresoli wrote:
>> Tables of struct reg_8 are used to simplify multi-byte register
>> assignment. However filling these snippets with values computed at
>> runtime is currently implemented by very similar functions doing the
>> needed shift & mask manipulation.
>>
>> Replace all those functions with a unique helper function to fill
>> reg_8 tables in a simple and clean way.
> 
> What's the purpose of writing these registers as multiple I²C writes, when
> this can be done as a single write (i.e. the address followed by two or
> three octets of data)?

Good point. The for loops applying the register values (the lines just
after those changed by my patch) defuse the regmap bulk write capability.

I guess this could be improved not filling any table, but directly
calling regmap_bulk_write(), passing the u16 or u32 register value with
proper endianness. No tables, less code. This would replace the present
patch with a shorter and more effective one. Is it what you was suggesting?

I'll try that.
-- 
Luca