On Fri, May 6, 2016 at 2:10 PM, Christian Lamparter
[off-list ref] wrote:

From: Álvaro Fernández Rojas <redacted>

This patch adds support for defining memory-mapped GPIOs which
are compatible with the existing gpio-mmio interface. The generic
library provides support for many memory-mapped GPIO controllers
that are found in various on-board FPGA and ASIC solutions that
are used to control board's switches, LEDs, chip-selects,
Ethernet/USB PHY power, etc.

For setting GPIO's there are three configurations:
        1. single input/output register resource (named "dat"),
        2. set/clear pair (named "set" and "clr"),
        3. single output register resource and single input resource
           ("set" and dat").

The configuration is detected by which resources are present.
For the single output register, this drives a 1 by setting a bit
and a zero by clearing a bit.  For the set clr pair, this drives
a 1 by setting a bit in the set register and clears it by setting
a bit in the clear register. The configuration is detected by
which resources are present.

For setting the GPIO direction, there are three configurations:
        a. simple bidirectional GPIOs that requires no configuration.
        b. an output direction register (named "dirout")
           where a 1 bit indicates the GPIO is an output.
        c. an input direction register (named "dirin")
           where a 1 bit indicates the GPIO is an input.

The first user for this binding is "wd,mbl-gpio".

Some (mostly) style issues below.

+ empty line

+       /* If ngpio property is not specified, of_property_read_u32
+        * will return -EINVAL. In this case the number of GPIOs is
+        * automatically determined by the register width. Any
+        * other error of of_property_read_u32 is due bad data and
+        * needs to be dealt with.

Couple style issues:
/*
 * First sentence starts here. func() are going with parens.
 */

+        */
+       err = of_property_read_u32(dev->of_node, "ngpio", &pdata->ngpio);
+       if (err && err != -EINVAL)
+               return err;
+
+       if (of_device_is_big_endian(dev->of_node))
+               *flags |= BGPIOF_BIG_ENDIAN_BYTE_ORDER;
+
+       if (of_property_read_bool(dev->of_node, "unreadable-reg-set"))
+               *flags |= BGPIOF_UNREADABLE_REG_SET;
+
+       if (of_property_read_bool(dev->of_node, "unreadable-reg-dir"))
+               *flags |= BGPIOF_UNREADABLE_REG_DIR;
+
+       if (of_property_read_bool(dev->of_node, "big-endian-byte-order"))
+               *flags |= BGPIOF_BIG_ENDIAN;
+
+       if (of_property_read_bool(dev->of_node, "read-output-reg-set"))
+               *flags |= BGPIOF_READ_OUTPUT_REG_SET;
+
+       if (of_property_read_bool(dev->of_node, "no-output"))
+               *flags |= BGPIOF_NO_OUTPUT;
+       return 0;
+}
+
+#define ADD_GPIO_OF(_name, _func) { .compatible = _name, .data = _func }
+
+static const struct of_device_id bgpio_of_match[] = {
+       ADD_GPIO_OF("wd,mbl-gpio", bgpio_basic_mmio_parse_dt),
+       { }
+};
+#undef ADD_GPIO_OF
+MODULE_DEVICE_TABLE(of, bgpio_of_match);
+
+static struct bgpio_pdata *bgpio_parse_dt(struct platform_device *pdev,
+                                         unsigned long *flags)
+{
+       const int (*parse_dt)(struct platform_device *,
+                             struct bgpio_pdata *, unsigned long *);
+       const struct device_node *node = pdev->dev.of_node;
+       const struct of_device_id *of_id;
+       struct bgpio_pdata *pdata;
+       int err = -ENODEV;

(1)

+
+       of_id = of_match_node(bgpio_of_match, node);
+       if (!of_id)
+               return NULL;

(2)

Why so?

+
+       pdata = devm_kzalloc(&pdev->dev, sizeof(struct bgpio_pdata),
+                            GFP_KERNEL);
+       if (!pdata)
+               return ERR_PTR(-ENOMEM);
+
+       parse_dt = (const void *)of_id->data;
+       if (parse_dt)
+               err = parse_dt(pdev, pdata, flags);
+       if (err)
+               return ERR_PTR(err);
+
+       return pdata;
+}
+#else
+static struct bgpio_pdata *bgpio_parse_dt(struct platform_device *pdev,
+                                         unsigned long *flags)
+{
+       return NULL;
+}
+#endif /* CONFIG_OF */

-- 
With Best Regards,
Andy Shevchenko
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