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SubjectRe: [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@intel.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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