Re: [PATCH v5 2/4] mfd: Add driver for Embedded Controller found on Acer Iconia Tab A500

From: Lee Jones <lee.jones@linaro.org>
To: Dmitry Osipenko <digetx@gmail.com>
Cc: Rob Herring <robh+dt@kernel.org>,
	Thierry Reding <thierry.reding@gmail.com>,
	Jonathan Hunter <jonathanh@nvidia.com>,
	Dan Murphy <dmurphy@ti.com>, Sebastian Reichel <sre@kernel.org>,
	devicetree@vger.kernel.org, linux-tegra@vger.kernel.org,
	linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v5 2/4] mfd: Add driver for Embedded Controller found on Acer Iconia Tab A500
Date: Mon, 16 Nov 2020 10:29:01 +0000	[thread overview]
Message-ID: <20201116102901.GO3718728@dell> (raw)
In-Reply-To: <0e795281-ca18-fca6-1585-a487bcfabb86@gmail.com>

On Mon, 16 Nov 2020, Dmitry Osipenko wrote:
> ...
> >>>> +	while (retries-- > 0) {
> >>>> +		ret = i2c_smbus_read_word_data(client, reg);
> >>>> +		if (ret >= 0)
> >>>> +			break;
> >>>> +
> >>>> +		msleep(A500_EC_I2C_ERR_TIMEOUT);
> >>>> +	}
> ...
> >>> I'm surprised there isn't a generic function which does this kind of
> >>> read.  Seems like pretty common/boilerplate stuff.
> >>
> >> I'm not quite sure that this is a really very common pattern which
> >> deserves a generic helper.
> > 
> > What?  Read from I2C a few times, then sleep sounds like a pretty
> > common pattern to me.
> 
> Maybe the read_poll_timeout() helper could be used for that, but I think
> the open-coded variant is much easier to perceive, don't you agree?

I haven't looked into it.  My comment was more general in nature.

As a general rule, helpers are better than open coding, but there are
always exceptions.  There may not even be a suitable helper for this
use-case.  As I say, the comment was more of a passing remark.

[...]

> >> These are the values which controller's firmware wants to see, otherwise
> >> it will reject command as invalid. I'll add a clarifying comment to the
> >> code.
> > 
> > Thanks.  Hopefully with a bit more information as to why the firmware
> > expects to see them.  Hopefully they're not random.
> 
> These are the firmware-defined specific command opcodes, I'll add
> defines for them to make it more clear, thanks.

That'll do.

-- 
Lee Jones [李琼斯]
Senior Technical Lead - Developer Services
Linaro.org │ Open source software for Arm SoCs
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