On Fri, Feb 11, 2022 at 10:19:24AM +0100, Javier Martinez Canillas wrote:
> This adds a DRM driver for SSD1305, SSD1306, SSD1307 and SSD1309 Solomon
> OLED display controllers.
> 
> It's only the core part of the driver and a bus specific driver is needed
> for each transport interface supported by the display controllers.

...

> +#include <linux/backlight.h>
> +#include <linux/bitfield.h>

bits.h
(FYI, specifically sent a patch few days ago to add explicitly the inclusions
 that needed for bitfield operations in the example inside bitfield.h).

> +#include <linux/delay.h>
> +#include <linux/gpio/consumer.h>
> +#include <linux/property.h>
> +#include <linux/pwm.h>
> +#include <linux/regulator/consumer.h>

...

> +#define SSD130X_SET_ADDRESS_MODE_HORIZONTAL  (0x00)
> +#define SSD130X_SET_ADDRESS_MODE_VERTICAL    (0x01)
> +#define SSD130X_SET_ADDRESS_MODE_PAGE                (0x02)
> +
> +#define SSD130X_SET_AREA_COLOR_MODE_ENABLE   (0x1e)
> +#define SSD130X_SET_AREA_COLOR_MODE_LOW_POWER        (0x05)

Do the parentheses add anything here?

...

> +/*
> + * Helper to write command (SSD130X_COMMAND). The fist variadic argument
> + * is the command to write and the following are the command options.

This is not correct explanation. Please, rephrase to show that _each_ of the
options is sent with a preceding command.

> + */
> +static int ssd130x_write_cmd(struct ssd130x_device *ssd130x, int count,
> +                                 /* u8 cmd, u8 option, ... */...)
> +{
> +     va_list ap;
> +     u8 value;
> +     int ret;
> +
> +     va_start(ap, count);
> +
> +     do {
> +             value = va_arg(ap, int);
> +             ret = regmap_write(ssd130x->regmap, SSD130X_COMMAND, (u8)value);
> +             if (ret)
> +                     goto out_end;
> +     } while (--count);
> +
> +out_end:
> +     va_end(ap);
> +
> +     return ret;
> +}

...

> +     if (ssd130x->device_info->need_pwm) {

Yeah, unfortunately we still don't have pwm_get_optional()...

> +             ret = ssd130x_pwm_enable(ssd130x);
> +             if (ret) {
> +                     dev_err(dev, "Failed to enable PWM: %d\n", ret);
> +                     regulator_disable(ssd130x->vcc_reg);
> +                     return ret;
> +             }
> +     }

...

> +static void ssd130x_power_off(struct ssd130x_device *ssd130x)
> +{

> +     if (ssd130x->device_info->need_pwm) {

Redundant check. The two below are NULL-aware.

> +             pwm_disable(ssd130x->pwm);
> +             pwm_put(ssd130x->pwm);
> +     }
> +
> +     regulator_disable(ssd130x->vcc_reg);
> +}

...

> +     ret = ssd130x_write_cmd(ssd130x, 2, SSD130X_SET_COM_PINS_CONFIG, 
> compins);
> +     if (ret < 0)
> +             return ret;

> +
> +

One blank line is enough.

...

> +     for (i = y / 8; i < y / 8 + pages; i++) {
> +             int m = 8;
> +
> +             /* Last page may be partial */
> +             if (8 * (i + 1) > ssd130x->height)
> +                     m = ssd130x->height % 8;

Perhaps it can be moved out of the loop with refactored piece below.

> +             for (j = x; j < x + width; j++) {
> +                     u8 data = 0;
> +
> +                     for (k = 0; k < m; k++) {
> +                             u8 byte = buf[(8 * i + k) * line_length + j / 
> 8];
> +                             u8 bit = (byte >> (j % 8)) & 1;
> +
> +                             data |= bit << k;
> +                     }
> +                     data_array[array_idx++] = data;
> +             }
> +     }

...

> +     bl = devm_backlight_device_register(dev, dev_name(dev), dev, ssd130x,
> +                                         &ssd130xfb_bl_ops, NULL);
> +     if (IS_ERR(bl)) {

> +             ret = PTR_ERR(bl);
> +             dev_err_probe(dev, ret, "Unable to register backlight 
> device\n");
> +             return ERR_PTR(ret);

                dev_err_probe(dev, PTR_ERR(bl), "Unable to register backlight 
device\n");
                return bl;

?

> +     }

-- 
With Best Regards,
Andy Shevchenko


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