linux-kernel - Re: [PATCH v2] rtc: isl12026: Add driver.

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Date:   Thu, 15 Feb 2018 14:45:11 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     David Daney <david.daney@...ium.com>
Cc:     Alessandro Zummo <a.zummo@...ertech.it>,
        Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>, linux-rtc@...r.kernel.org,
        devicetree <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] rtc: isl12026: Add driver.

On Wed, Feb 14, 2018 at 2:55 AM, David Daney <david.daney@...ium.com> wrote:
> The ISL12026 is a combination RTC and EEPROM device with I2C
> interface.  The standard RTC driver interface is provided.  The EEPROM
> is accessed via the NVMEM interface via the "eeprom0" directory in the
> sysfs entry for the device.

Thanks for an update, my comments below.

> +struct isl12026 {
> +       struct rtc_device *rtc;
> +       struct i2c_client *nvm_client;
> +       struct nvmem_config nvm_cfg;
> +       /*
> +        * RTC write operations require that multiple messages be
> +        * transmitted, we hold the lock for all accesses to the
> +        * device so that these sequences cannot be disrupted.  Also,

> +        * the write cycle to the nvmem takes many mS during which the

What mS means? milliseconds? The standard abbreviation for it 'ms'.

> +        * device does not respond to commands, so holding the lock
> +        * also prevents access during these times.
> +        */
> +       struct mutex lock;
> +};

> +static int isl12026_read_reg(struct i2c_client *client, int reg)
> +{

> +       ret = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
> +       if (ret != ARRAY_SIZE(msgs)) {
> +               dev_err(&client->dev, "read reg error, ret=%d\n", ret);
> +               ret = ret < 0 ? ret : -EIO;
> +       } else {
> +               ret = val;
> +       }

> +       return val;

Something wrong. ret is not used after all.

> +}

Check entire code for such.

> +       /* 2 bytes of address, most significant first */
> +       addr[0] = (offset >> 8) & 0xff;
> +       addr[1] = offset & 0xff;

Consider to drop '& 0xff', they are pointless (you have u8 type).

> +               payload[0] = (offset >> 8) & 0xff;
> +               payload[1] = offset & 0xff;

Ditto.

> +static void isl12026_force_power_modes(struct i2c_client *client)
> +{
> +       int ret;
> +       int pwr, requested_pwr;
> +       u32 bsw_val, sbib_val;

> +       bool set_bsw, set_sbib;
> +

> +       ret = of_property_read_u32(client->dev.of_node,
> +                                  "isil,pwr-bsw", &bsw_val);
> +       set_bsw = (ret == 0);

Which is not fully correct. Better to do

set_bsw = of_property_present();

ret = of_property_read...();
if (ret)
  return ret;

> +
> +       ret = of_property_read_u32(client->dev.of_node,
> +                                  "isil,pwr-sbib", &sbib_val);
> +       set_sbib = (ret == 0);

Ditto.

> +
> +       /* Check if PWR.BSW and/or PWR.SBIB need specified values */
> +

> +       if (set_bsw || set_sbib) {

if (!x && !y)
 return;

> +               pwr = isl12026_read_reg(client, ISL12026_REG_PWR);
> +               if (pwr < 0) {
> +                       dev_err(&client->dev,
> +                               "Error: Failed to read PWR %d\n", pwr);
> +                       return;
> +               }
> +
> +               requested_pwr = pwr;
> +
> +               if (set_bsw) {
> +                       if (bsw_val)
> +                               requested_pwr |= ISL12026_REG_PWR_BSW;
> +                       else
> +                               requested_pwr &= ~ISL12026_REG_PWR_BSW;
> +               }

Undefined state if no value?

> +               if (set_sbib) {
> +                       if (sbib_val)
> +                               requested_pwr |= ISL12026_REG_PWR_SBIB;
> +                       else
> +                               requested_pwr &= ~ISL12026_REG_PWR_SBIB;
> +               }

Ditto.

> +
> +               if (pwr >= 0 && pwr != requested_pwr) {

> +                       dev_info(&client->dev, "PWR: %02x\n", (u8)pwr);
> +                       dev_info(&client->dev,
> +                                "Updating PWR to: %02x\n", (u8)requested_pwr);
> +                       isl12026_write_reg(client,
> +                                          ISL12026_REG_PWR, requested_pwr);

If you do explicit casting in printf() parameters you are doing
something wrong in 99.9% cases.

> +               }
> +       }
> +}

> +static int isl12026_probe_new(struct i2c_client *client)
> +{
> +       struct isl12026 *priv;
> +       int ret;


> +       /* The NVMem array responds at i2c address 0x57 */
> +       priv->nvm_client = i2c_new_dummy(client->adapter, 0x57);

Magic. Make it #define and put comment there.

> +       if (!priv->nvm_client)
> +               return -ENOMEM;

> +}

> +#ifdef CONFIG_OF

Remove this ugly #ifdef. Your driver OF only one.

> +static const struct of_device_id isl12026_dt_match[] = {
> +       { .compatible = "isil,isl12026" },
> +       { },
> +};
> +MODULE_DEVICE_TABLE(of, isl12026_dt_match);

> +#endif

> +               .of_match_table = of_match_ptr(isl12026_dt_match),

Drop of_match_ptr().

-- 
With Best Regards,
Andy Shevchenko