linux-kernel - Re: [PATCH v4 1/3] mfd: Add new mfd device TPS68470

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Date:   Wed, 26 Jul 2017 09:20:39 +0100
From:   Lee Jones <lee.jones@...aro.org>
To:     "Mani, Rajmohan" <rajmohan.mani@...el.com>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        "linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Alexandre Courbot <gnurou@...il.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>,
        "sakari.ailus@...ux.intel.com" <sakari.ailus@...ux.intel.com>,
        Andy Shevchenko <andy.shevchenko@...il.com>
Subject: Re: [PATCH v4 1/3] mfd: Add new mfd device TPS68470

On Tue, 25 Jul 2017, Mani, Rajmohan wrote:

> Hi Lee,
> 
> > Subject: Re: [PATCH v4 1/3] mfd: Add new mfd device TPS68470
> > 
> > On Fri, 21 Jul 2017, Mani, Rajmohan wrote:
> > > > On Wed, 19 Jul 2017, Rajmohan Mani wrote:
> > > >
> > > > > The TPS68470 device is an advanced power management unit that
> > > > > powers
> > > > a
> > > > > Compact Camera Module (CCM), generates clocks for image sensors,
> > > > > drives a dual LED for Flash and incorporates two LED drivers for
> > > > > general purpose indicators.
> > > > >
> > > > > This patch adds support for TPS68470 mfd device.
> > > > >
> > > > > Signed-off-by: Rajmohan Mani <rajmohan.mani@...el.com>
> > > > > ---
> > > > >  drivers/mfd/Kconfig          |  18 +++++++
> > > > >  drivers/mfd/Makefile         |   1 +
> > > > >  drivers/mfd/tps68470.c       | 110
> > > > +++++++++++++++++++++++++++++++++++++++++++
> > > > >  include/linux/mfd/tps68470.h |  97
> > > > > ++++++++++++++++++++++++++++++++++++++
> > > > >  4 files changed, 226 insertions(+)  create mode 100644
> > > > > drivers/mfd/tps68470.c  create mode 100644
> > > > > include/linux/mfd/tps68470.h
> > 
> > [...]
> > 
> > > > > +static const struct regmap_config tps68470_regmap_config = {
> > > > > +	.reg_bits = 8,
> > > > > +	.val_bits = 8,
> > > > > +	.max_register = TPS68470_REG_MAX, };
> > > > > +
> > > > > +static int tps68470_chip_init(struct device *dev, struct regmap
> > > > > +*regmap) {
> > > > > +	unsigned int version;
> > > > > +	int ret;
> > > > > +
> > > > > +	/* Force software reset */
> > > > > +	ret = regmap_write(regmap, TPS68470_REG_RESET,
> > > > TPS68470_REG_RESET_MASK);
> > > > > +	if (ret < 0)
> > > >
> > > > Will 'if (!ret)' do?
> > > >
> > >
> > > We intend to check error conditions and bail out. So, if (ret < 0) works for
> > this.
> > 
> > Yes, 'if (!ret)' does that too.
> > 
> 
> regmap_write() and regmap_read() functions return 0 on success. Hence we can not use 'if (!ret)' here, since we check for error conditions.

Sorry, this was a typo.

It should be 'if (ret)'.

What I'm trying to get at is the " < 0" is not required.

> > > > > +		return ret;
> > > > > +
> > > > > +	ret = regmap_read(regmap, TPS68470_REG_REVID, &version);
> > > > > +	if (ret < 0) {
> > > >
> > > > Same
> > > >
> > >
> > > We intend to check error conditions and bail out. So, if (ret < 0) works for
> > this.
> > 
> > As above.
> > 
> 
> Same as above
> 
> > > > > +		dev_err(dev, "Failed to read revision register: %d\n", ret);
> > > > > +		return ret;
> > > > > +	}
> > > > > +
> > > > > +	dev_info(dev, "TPS68470 REVID: 0x%x\n", version);
> > > > > +
> > > > > +	return 0;
> > > > > +}
> > > > > +
> > > > > +static int tps68470_probe(struct i2c_client *client) {
> > > > > +	struct device *dev = &client->dev;
> > > > > +	struct regmap *regmap;
> > > > > +	int ret;
> > > > > +
> > > > > +	regmap = devm_regmap_init_i2c(client, &tps68470_regmap_config);
> > > > > +	if (IS_ERR(regmap)) {
> > > > > +		dev_err(dev, "devm_regmap_init_i2c Error %ld\n",
> > > > > +			PTR_ERR(regmap));
> > > > > +		return PTR_ERR(regmap);
> > > > > +	}
> > > > > +
> > > > > +	i2c_set_clientdata(client, regmap);
> > > > > +
> > > > > +	ret = tps68470_chip_init(dev, regmap);
> > > > > +	if (ret < 0) {
> > > >
> > > > Same
> > > >
> > >
> > > We intend to check error conditions and bail out. So, if (ret < 0) works for
> > this.
> > 
> > As above.
> > 
> 
> Same as above

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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