On Thu, Dec 15, 2016 at 12:12 AM, Sebastien Bourdelin
[off-list ref] wrote:

This driver implements a GPIOs bit-banged bus, called the NBUS by
Technologic Systems. It is used to communicate with the peripherals in
the FPGA on the TS-4600 SoM.

Signed-off-by: Sebastien Bourdelin <redacted>

(...)

+#include <linux/gpio.h>

Use:
#include <linux/gpio/consumer.h>
instead, and deal with the fallout.

+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/of.h>
+#include <linux/of_gpio.h>

Don't use this.

+#include <linux/platform_device.h>
+#include <linux/pwm.h>
+
+static DEFINE_MUTEX(ts_nbus_lock);
+static bool ts_nbus_ready;

Why not move this to the struct ts_nbus state container?

It seems to be per-bus not per-system.

+#define TS_NBUS_READ_MODE  0
+#define TS_NBUS_WRITE_MODE 1
+#define TS_NBUS_DIRECTION_IN  0
+#define TS_NBUS_DIRECTION_OUT 1
+#define TS_NBUS_WRITE_ADR 0
+#define TS_NBUS_WRITE_VAL 1
+
+struct ts_nbus {
+       struct pwm_device *pwm;
+       int num_data;
+       int *data;
+       int csn;
+       int txrx;
+       int strobe;
+       int ale;
+       int rdy;
+};
+
+static struct ts_nbus *ts_nbus;

Nopes. No singletons please.

Use the state container pattern:
Documentation/driver-model/design-patterns.txt

+/*
+ * request all gpios required by the bus.
+ */
+static int ts_nbus_init(struct platform_device *pdev)
+{
+       int err;
+       int i;
+
+       for (i = 0; i < ts_nbus->num_data; i++) {
+               err = devm_gpio_request_one(&pdev->dev, ts_nbus->data[i],
+                                           GPIOF_OUT_INIT_HIGH,
+                                           "TS NBUS data");
+               if (err)
+                       return err;
+       }

DO not use the legacy GPIO API anywhere.

Reference the device and use gpiod_get() simple, fair and square.

Store struct gpio_desc * pointers in your state container instead.

+static int ts_nbus_get_of_pdata(struct device *dev, struct device_node *np)
+{
+       int num_data;
+       int *data;
+       int ret;
+       int i;
+
+       ret = of_gpio_named_count(np, "data-gpios");
+       if (ret < 0) {
+               dev_err(dev,
+                       "failed to count GPIOs in DT property data-gpios\n");
+               return ret;
+       }

Do not reinvent the wheel.

Use devm_gpiod_get_array().

+       ret = of_get_named_gpio(np, "csn-gpios", 0);

And again use devm_gpiod_get(), and gpiod_* accessors.
Applies everywhere.

Yours,
Linus Walleij