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

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Message-ID: <20180627093055.fn6gqpaodzxmhhx3@valkosipuli.retiisi.org.uk>
Date:   Wed, 27 Jun 2018 12:30:55 +0300
From:   Sakari Ailus <sakari.ailus@....fi>
To:     Luca Ceresoli <luca@...aceresoli.net>
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

On Wed, Jun 27, 2018 at 10:13:12AM +0200, Luca Ceresoli wrote:
> 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?

Yes, please.

-- 
Sakari Ailus
e-mail: sakari.ailus@....fi