Re: [PATCH v8 1/2] mfd: bd71837: mfd driver for ROHM BD71837 PMIC

[Matti Vaittinen]

On Wed, Jul 04, 2018 at 11:39:11AM +0300, Matti Vaittinen wrote:
> On Tue, Jul 03, 2018 at 11:26:00AM +0200, Enric Balletbo Serra wrote:
> > Missatge de Matti Vaittinen <matti.vaittinen@xxxxxxxxxxxxxxxxx> del
> > dia dv., 29 de juny 2018 a les 11:47:
> > 
> > Now that you use devm calls and you don't need to unwind things I
> > think is better to use plain returns. So,
> > 
> > return -ENOMEM;
> 
> I have never really understood why use of gotos in error handling is
> discouraged. Personally I would always choose single point of exit from
> a function when it is simple enough to achieve (like in this case). I've
> written and fixed way too many functions which leak resources or
> accidentally keep a lock when exiting from error branches. But I know
> many colleagues like you who prefer not to have gotos but  in place returns
> instead. So I guess I'll leave the final call on this to the one who is
> maintainer for this code. And it is true there is no things to unwind
> now - which does not mean that next updater won't add such. But as I
> said, I know plenty of people share your view - and even though I rather
> maintain code with only one exit the final call is on subsystem maintainer
> here.

Actually, If it was completely my call the probe would look something
like this:

+static int bd71837_i2c_probe(struct i2c_client *i2c,
+                           const struct i2c_device_id *id)
+{
+       struct bd71837 *bd71837;
+       struct bd71837_board *board_info;
+       int gpio_intr = 0;
+
+       const char *errstr = "No IRQ configured";
+       int ret = -EINVAL;
+
+       bd71837 = devm_kzalloc(&i2c->dev, sizeof(struct bd71837), GFP_KERNEL);
+
+       if (bd71837 == NULL)
+               return -ENOMEM;
+
+       board_info = dev_get_platdata(&i2c->dev);
+
+       if (!board_info)
+               gpio_intr = i2c->irq;
+       else
+               gpio_intr = board_info->gpio_intr;
+
+       if (!gpio_intr)
+               goto err_out;
+
+       i2c_set_clientdata(i2c, bd71837);
+       bd71837->dev = &i2c->dev;
+       bd71837->i2c_client = i2c;
+       bd71837->chip_irq = gpio_intr;
+
+       errstr = "regmap initialization failed";
+
+       bd71837->regmap = devm_regmap_init_i2c(i2c, &bd71837_regmap_config);
+       ret = PTR_ERR(bd71837->regmap);
+       if (IS_ERR(bd71837->regmap))
+               goto err_out;
+
+       errstr = "Read BD71837_REG_DEVICE failed";
+       ret = bd71837_reg_read(bd71837, BD71837_REG_REV);
+       if (ret < 0)
+               goto err_out;
+
+       errstr = "Failed to add irq_chip";
+       ret = devm_regmap_add_irq_chip(&i2c->dev, bd71837->regmap,
+                                      bd71837->chip_irq, IRQF_ONESHOT, 0,
+                                      &bd71837_irq_chip, &bd71837->irq_data);
+       if (ret < 0)
+               goto err_out;
+
+       errstr = "Failed to configure button short press timeout";
+       ret = regmap_update_bits(bd71837->regmap,
+                                BD71837_REG_PWRONCONFIG0,
+                                BD718XX_PWRBTN_PRESS_DURATION_MASK,
+                                BD718XX_PWRBTN_SHORT_PRESS_10MS);
+       if (ret < 0)
+               goto err_out;
+
+       /* According to BD71847 datasheet the HW default for long press
+        * detection is 10ms. So lets change it to 10 sec so we can actually
+        * get the short push and allow gracefull shut down
+        */
+       ret = regmap_update_bits(bd71837->regmap,
+                                BD71837_REG_PWRONCONFIG1,
+                                BD718XX_PWRBTN_PRESS_DURATION_MASK,
+                                BD718XX_PWRBTN_LONG_PRESS_10S);
+
+       errstr = "Failed to configure button long press timeout";
+       if (ret < 0)
+               goto err_out;
+
+       btns[0].irq = regmap_irq_get_virq(bd71837->irq_data,
+                                         BD71837_INT_PWRBTN_S);
+
+       errstr = "Failed to get the IRQ";
+       ret = btns[0].irq;
+       if (btns[0].irq < 0)
+               goto err_out;
+
+       errstr = "Failed to create subdevices";
+       ret = devm_mfd_add_devices(bd71837->dev, PLATFORM_DEVID_AUTO,
+                                  bd71837_mfd_cells,
+                                  ARRAY_SIZE(bd71837_mfd_cells), NULL, 0,
+                                  regmap_irq_get_domain(bd71837->irq_data));
+       if (ret) {
+err_out:
+               if (errstr)
+                       dev_err(&i2c->dev, "%s (%d)\n", errstr, ret);
+       }
+
+       return ret;
+}

What do you think of this? To my eye it is nice. It keeps single point of
exit and introduces only simple if-statements without the need of curly
brackets. And finally the error prints string works as a comment too.
I've seen bunch of constructs like this on the networking side but I
have no idea if this is frowned on this subsystem =) Oh, and probe abowe
is just to illustrate the idea, I did not even try compiling it yet.

Best Regards
    Matti Vaittinen