diff mbox series

[RFC,19/25] leds: tm1628: Add 7-segment display support

Message ID 20191212033952.5967-20-afaerber@suse.de (mailing list archive)
State New, archived
Headers show
Series arm64: realtek: Add Xnano X5 and implement TM1628/FD628/AiP1618 LED controllers | expand

Commit Message

Andreas Färber Dec. 12, 2019, 3:39 a.m. UTC 
Detect DT child nodes covering more than one LED component and implement
a text to 7-segment display mapping.

Signed-off-by: Andreas Färber <afaerber@suse.de>
---
 drivers/leds/leds-tm1628.c | 230 ++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 229 insertions(+), 1 deletion(-)

Comments

Geert Uytterhoeven Dec. 12, 2019, 8:33 a.m. UTC | #1 
Hi Andreas,

On Thu, Dec 12, 2019 at 4:42 AM Andreas Färber <afaerber@suse.de> wrote:
> Detect DT child nodes covering more than one LED component and implement
> a text to 7-segment display mapping.
>
> Signed-off-by: Andreas Färber <afaerber@suse.de>

> --- a/drivers/leds/leds-tm1628.c
> +++ b/drivers/leds/leds-tm1628.c

> +static const struct tm1628_ssd_char tm1628_char_ssd_map[] = {
> +       { '0', SSD_TOP | SSD_TOP_LEFT | SSD_TOP_RIGHT |
> +              SSD_BOTTOM_LEFT | SSD_BOTTOM_RIGHT | SSD_BOTTOM },

Please use include/uapi/linux/map_to_7segment.h
Yes, it is well hidden ;-).

Gr{oetje,eeting}s,

                        Geert
Andreas Färber Dec. 12, 2019, 2:10 p.m. UTC | #2 
Hi Geert,

Am 12.12.19 um 09:33 schrieb Geert Uytterhoeven:
> On Thu, Dec 12, 2019 at 4:42 AM Andreas Färber <afaerber@suse.de> wrote:
>> Detect DT child nodes covering more than one LED component and implement
>> a text to 7-segment display mapping.
>>
>> Signed-off-by: Andreas Färber <afaerber@suse.de>
> 
>> --- a/drivers/leds/leds-tm1628.c
>> +++ b/drivers/leds/leds-tm1628.c
> 
>> +static const struct tm1628_ssd_char tm1628_char_ssd_map[] = {
>> +       { '0', SSD_TOP | SSD_TOP_LEFT | SSD_TOP_RIGHT |
>> +              SSD_BOTTOM_LEFT | SSD_BOTTOM_RIGHT | SSD_BOTTOM },
> 
> Please use include/uapi/linux/map_to_7segment.h
> Yes, it is well hidden ;-).

Many thanks for that pointer! Even matches the segment/bit order of my
datasheets/defines.

The small t may be different (T?), and I don't see it mapping combined
characters (patch 22/25). The recommended sysfs map_7seg attribute may
help deal with that, but seems terribly unhandy for my busybox initrd.

Hope you also read the cover letter, where not finding this and many
other issues were discussed. I was expecting some .c file in either
drivers/leds or auxdisplay - input is indeed unexpected for output.

Still wondering whether we can somehow describe those "VFD" displays in
a more reusable way, like we do for MIPI DSI panels.

Cheers,
Andreas
Pavel Machek Dec. 21, 2019, 8:23 p.m. UTC | #3 
Hi!

> Detect DT child nodes covering more than one LED component and implement
> a text to 7-segment display mapping.

Up to here, I seen nothing totally crazy.

But I'd prefer not to have this in the LED subsystem.

Best regards,
									Pavel

> Signed-off-by: Andreas Färber <afaerber@suse.de>
> ---
>  drivers/leds/leds-tm1628.c | 230 ++++++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 229 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/leds/leds-tm1628.c b/drivers/leds/leds-tm1628.c
> index 8a8fd1562853..e2c2a5d91596 100644
> --- a/drivers/leds/leds-tm1628.c
> +++ b/drivers/leds/leds-tm1628.c
> @@ -47,6 +47,15 @@ struct tm1628_info {
>  	int				default_pwm;
>  };
>  
> +struct tm1628_segment {
> +	u32 grid;
> +	u32 seg;
> +};
> +
> +struct tm1628_display {
> +	struct tm1628_segment segments[8];
> +};
> +
>  struct tm1628_led {
>  	struct led_classdev	leddev;
>  	struct tm1628		*ctrl;
> @@ -62,6 +71,8 @@ struct tm1628 {
>  	int				mode_index;
>  	int				pwm_index;
>  	u8				data[14];
> +	unsigned int			num_displays;
> +	struct tm1628_display		*displays;
>  	unsigned int			num_leds;
>  	struct tm1628_led		leds[];
>  };
> @@ -253,6 +264,215 @@ static int tm1628_register_led(struct tm1628 *s,
>  	return devm_led_classdev_register_ext(dev, &led->leddev, &init_data);
>  }
>  
> +#define SSD_TOP			BIT(0)
> +#define SSD_TOP_RIGHT		BIT(1)
> +#define SSD_BOTTOM_RIGHT	BIT(2)
> +#define SSD_BOTTOM		BIT(3)
> +#define SSD_BOTTOM_LEFT		BIT(4)
> +#define SSD_TOP_LEFT		BIT(5)
> +#define SSD_MIDDLE		BIT(6)
> +#define SSD_DOT			BIT(7)
> +
> +struct tm1628_ssd_char {
> +	char ch;
> +	u8 segs;
> +};
> +
> +static const struct tm1628_ssd_char tm1628_char_ssd_map[] = {
> +	{ '0', SSD_TOP | SSD_TOP_LEFT | SSD_TOP_RIGHT |
> +	       SSD_BOTTOM_LEFT | SSD_BOTTOM_RIGHT | SSD_BOTTOM },
> +	{ '1', SSD_TOP_RIGHT | SSD_BOTTOM_RIGHT },
> +	{ '2', SSD_TOP | SSD_TOP_RIGHT | SSD_MIDDLE | SSD_BOTTOM_LEFT | SSD_BOTTOM },
> +	{ '3', SSD_TOP | SSD_TOP_RIGHT | SSD_MIDDLE | SSD_BOTTOM_RIGHT | SSD_BOTTOM },
> +	{ '4', SSD_TOP_LEFT | SSD_TOP_RIGHT | SSD_MIDDLE | SSD_BOTTOM_RIGHT },
> +	{ '5', SSD_TOP | SSD_TOP_LEFT | SSD_MIDDLE | SSD_BOTTOM_RIGHT | SSD_BOTTOM },
> +	{ '6', SSD_TOP | SSD_TOP_LEFT | SSD_MIDDLE | SSD_BOTTOM_LEFT | SSD_BOTTOM_RIGHT | SSD_BOTTOM },
> +	{ '7', SSD_TOP | SSD_TOP_RIGHT | SSD_BOTTOM_RIGHT },
> +	{ '8', SSD_TOP | SSD_TOP_LEFT | SSD_TOP_RIGHT | SSD_MIDDLE |
> +	       SSD_BOTTOM_LEFT | SSD_BOTTOM_RIGHT | SSD_BOTTOM },
> +	{ '9', SSD_TOP | SSD_TOP_LEFT | SSD_TOP_RIGHT | SSD_MIDDLE |
> +	       SSD_BOTTOM_RIGHT | SSD_BOTTOM },
> +	{ 'A', SSD_TOP | SSD_TOP_LEFT | SSD_TOP_RIGHT | SSD_MIDDLE |
> +	       SSD_BOTTOM_LEFT | SSD_BOTTOM_RIGHT },
> +	{ 'B', SSD_TOP | SSD_TOP_LEFT | SSD_TOP_RIGHT | SSD_MIDDLE |
> +	       SSD_BOTTOM_LEFT | SSD_BOTTOM_RIGHT | SSD_BOTTOM },
> +	{ 'C', SSD_TOP | SSD_TOP_LEFT | SSD_BOTTOM_LEFT | SSD_BOTTOM },
> +	{ 'D', SSD_TOP | SSD_TOP_LEFT | SSD_TOP_RIGHT |
> +	       SSD_BOTTOM_LEFT | SSD_BOTTOM_RIGHT | SSD_BOTTOM },
> +	{ 'E', SSD_TOP | SSD_TOP_LEFT | SSD_MIDDLE | SSD_BOTTOM_LEFT | SSD_BOTTOM },
> +	{ 'F', SSD_TOP | SSD_TOP_LEFT | SSD_MIDDLE | SSD_BOTTOM_LEFT },
> +	{ 'G', SSD_TOP | SSD_TOP_LEFT | SSD_BOTTOM_LEFT | SSD_BOTTOM | SSD_BOTTOM_RIGHT },
> +	{ 'H', SSD_TOP_LEFT | SSD_TOP_RIGHT | SSD_MIDDLE |
> +	       SSD_BOTTOM_LEFT | SSD_BOTTOM_RIGHT },
> +	{ 'I', SSD_TOP_LEFT | SSD_BOTTOM_LEFT },
> +	{ 'J', SSD_TOP | SSD_TOP_RIGHT | SSD_BOTTOM_RIGHT | SSD_BOTTOM },
> +	{ 'K', SSD_TOP_LEFT | SSD_TOP_RIGHT | SSD_MIDDLE |
> +	       SSD_BOTTOM_LEFT | SSD_BOTTOM_RIGHT },
> +	{ 'L', SSD_TOP_LEFT | SSD_BOTTOM_LEFT | SSD_BOTTOM },
> +	{ 'O', SSD_TOP | SSD_TOP_LEFT | SSD_TOP_RIGHT |
> +	       SSD_BOTTOM_LEFT | SSD_BOTTOM_RIGHT | SSD_BOTTOM },
> +	{ 'P', SSD_TOP | SSD_TOP_LEFT | SSD_TOP_RIGHT | SSD_MIDDLE |
> +	       SSD_BOTTOM_LEFT },
> +	{ 'Q', SSD_TOP | SSD_TOP_LEFT | SSD_TOP_RIGHT |
> +	       SSD_BOTTOM_LEFT | SSD_BOTTOM_RIGHT | SSD_BOTTOM },
> +	{ 'R', SSD_TOP | SSD_TOP_LEFT | SSD_TOP_RIGHT | SSD_MIDDLE |
> +	       SSD_BOTTOM_LEFT | SSD_BOTTOM_RIGHT },
> +	{ 'S', SSD_TOP | SSD_TOP_LEFT | SSD_MIDDLE | SSD_BOTTOM_RIGHT | SSD_BOTTOM },
> +	{ 'T', SSD_TOP | SSD_TOP_LEFT | SSD_BOTTOM_LEFT },
> +	{ 'U', SSD_TOP_LEFT | SSD_BOTTOM_LEFT | SSD_BOTTOM | SSD_BOTTOM_RIGHT | SSD_TOP_RIGHT },
> +	{ 'V', SSD_TOP_LEFT | SSD_BOTTOM_LEFT | SSD_BOTTOM | SSD_BOTTOM_RIGHT | SSD_TOP_RIGHT },
> +	{ 'W', SSD_TOP_LEFT | SSD_BOTTOM_LEFT | SSD_BOTTOM | SSD_BOTTOM_RIGHT | SSD_TOP_RIGHT },
> +	{ 'Z', SSD_TOP | SSD_TOP_RIGHT | SSD_MIDDLE | SSD_BOTTOM_LEFT | SSD_BOTTOM },
> +	{ 'b', SSD_TOP_LEFT | SSD_MIDDLE | SSD_BOTTOM_LEFT | SSD_BOTTOM | SSD_BOTTOM_RIGHT },
> +	{ 'l', SSD_TOP_LEFT | SSD_BOTTOM_LEFT },
> +	{ 'o', SSD_MIDDLE | SSD_BOTTOM_LEFT | SSD_BOTTOM | SSD_BOTTOM_RIGHT },
> +	{ 't', SSD_TOP_LEFT | SSD_MIDDLE | SSD_BOTTOM_LEFT | SSD_BOTTOM },
> +	{ 'u', SSD_BOTTOM_LEFT | SSD_BOTTOM | SSD_BOTTOM_RIGHT },
> +	{ 'v', SSD_BOTTOM_LEFT | SSD_BOTTOM | SSD_BOTTOM_RIGHT },
> +	{ 'w', SSD_BOTTOM_LEFT | SSD_BOTTOM | SSD_BOTTOM_RIGHT },
> +	{ '-', SSD_MIDDLE },
> +	{ '_', SSD_BOTTOM },
> +	{ '.', SSD_DOT },
> +};
> +
> +static u8 tm1628_get_char_ssd_map(char ch)
> +{
> +	int i;
> +
> +	for (i = 0; i < ARRAY_SIZE(tm1628_char_ssd_map); i++) {
> +		if (tm1628_char_ssd_map[i].ch == ch)
> +			return tm1628_char_ssd_map[i].segs;
> +	}
> +
> +	return 0x0;
> +}
> +
> +static int tm1628_display_apply_map(struct tm1628 *s,
> +	struct tm1628_display *display, u8 map)
> +{
> +	struct tm1628_segment *segment;
> +	int i;
> +
> +	for (i = 0; i < 8; i++) {
> +		segment = &display->segments[i];
> +		tm1628_set_led(s, segment->grid, segment->seg, map & BIT(i));
> +	}
> +
> +	return 0;
> +}
> +
> +static ssize_t text_store(struct device *dev,
> +	struct device_attribute *attr, const char *buf, size_t count)
> +{
> +	struct tm1628 *s = dev_get_drvdata(dev);
> +	size_t offset, len = count;
> +	u8 map;
> +	int i, ret;
> +
> +	if (len > 0 && buf[len - 1] == '\n')
> +		len--;
> +
> +	for (i = 0, offset = 0; i < s->num_displays; i++) {
> +		if (offset < len) {
> +			map = tm1628_get_char_ssd_map(buf[offset]);
> +			offset++;
> +		} else
> +			map = 0x0;
> +
> +		tm1628_display_apply_map(s, &s->displays[i], map);
> +	}
> +
> +	ret = tm1628_set_address(s->spi, 0x0);
> +	if (ret)
> +		return ret;
> +
> +	ret = tm1628_write_data(s->spi, s->data, 14);
> +	if (ret)
> +		return ret;
> +
> +	return count;
> +}
> +
> +static struct device_attribute tm1628_attr =
> +	__ATTR_WO(text);
> +
> +static int tm1628_register_display(struct tm1628 *s,
> +	struct fwnode_handle *node)
> +{
> +	struct device *dev = &s->spi->dev;
> +	struct tm1628_display *display;
> +	u32 *reg;
> +	u32 grid, seg;
> +	int i, j, ret, reg_count;
> +
> +	reg_count = fwnode_property_count_u32(node, "reg");
> +	if (reg_count < 0)
> +		return reg_count;
> +
> +	if (reg_count % 2) {
> +		dev_warn(dev, "Ignoring extra cell in %s reg property\n",
> +			 fwnode_get_name(node));
> +		reg_count--;
> +	}
> +
> +	if (s->displays) {
> +		dev_warn(dev, "Only one display supported\n");
> +		return -EINVAL;
> +	}
> +
> +	s->num_displays = reg_count >> 1;
> +
> +	reg = devm_kzalloc(dev, reg_count * sizeof(*reg), GFP_KERNEL);
> +	if (!reg)
> +		return -ENOMEM;
> +
> +	ret = fwnode_property_read_u32_array(node, "reg", reg, reg_count);
> +	if (ret) {
> +		dev_err(dev, "Reading %s reg property failed (%d)\n",
> +			fwnode_get_name(node), ret);
> +		return ret;
> +	}
> +
> +	s->displays = devm_kzalloc(dev, s->num_displays * sizeof(*s->displays), GFP_KERNEL);
> +	if (!s->displays)
> +		return -ENOMEM;
> +
> +	for (i = 0; i < s->num_displays; i++) {
> +		display = &s->displays[i];
> +		grid = reg[i * 2];
> +		seg  = reg[i * 2 + 1];
> +		if (grid == 0 && seg != 0) {
> +			if (!tm1628_is_valid_seg(s, seg)) {
> +				dev_warn(dev, "%s reg out of range\n", fwnode_get_name(node));
> +				return -EINVAL;
> +			}
> +			grid = s->info->modes[s->mode_index].grid_mask;
> +			for (j = 0; grid && j < 7; j++) {
> +				display->segments[j].seg = seg;
> +				display->segments[j].grid = __ffs(grid);
> +				grid &= ~BIT(display->segments[j].grid);
> +			}
> +		} else if (grid != 0 && seg == 0) {
> +			if (!tm1628_is_valid_grid(s, grid)) {
> +				dev_warn(dev, "%s reg out of range\n", fwnode_get_name(node));
> +				return -EINVAL;
> +			}
> +			seg = s->info->modes[s->mode_index].seg_mask;
> +			for (j = 0; seg && j < 8; j++) {
> +				display->segments[j].grid = grid;
> +				display->segments[j].seg = __ffs(seg);
> +				seg &= ~BIT(display->segments[j].seg);
> +			}
> +		}
> +	}
> +
> +	devm_kfree(dev, reg);
> +
> +	device_create_file(dev, &tm1628_attr);
> +
> +	return 0;
> +}
> +
>  /* Work around __builtin_popcount() */
>  static u32 tm1628_grid_popcount(u8 grid_mask)
>  {
> @@ -325,7 +545,7 @@ static int tm1628_spi_probe(struct spi_device *spi)
>  			return ret;
>  		}
>  
> -		if (fwnode_property_count_u32(child, "reg") == 2) {
> +		if (reg[0] != 0 && reg[1] != 0 && fwnode_property_count_u32(child, "reg") == 2) {
>  			ret = tm1628_register_led(s, child, reg[0], reg[1], &s->leds[i++]);
>  			if (ret && ret != -EINVAL) {
>  				dev_err(&spi->dev, "Failed to register LED %s (%d)\n",
> @@ -334,6 +554,14 @@ static int tm1628_spi_probe(struct spi_device *spi)
>  				return ret;
>  			}
>  			s->num_leds++;
> +		} else {
> +			ret = tm1628_register_display(s, child);
> +			if (ret) {
> +				dev_err(&spi->dev, "Failed to register display %s (%d)\n",
> +					fwnode_get_name(child), ret);
> +				fwnode_handle_put(child);
> +				return ret;
> +			}
>  		}
>  	}
>
diff mbox series

Patch

diff --git a/drivers/leds/leds-tm1628.c b/drivers/leds/leds-tm1628.c
index 8a8fd1562853..e2c2a5d91596 100644
--- a/drivers/leds/leds-tm1628.c
+++ b/drivers/leds/leds-tm1628.c
@@ -47,6 +47,15 @@  struct tm1628_info {
 	int				default_pwm;
 };
 
+struct tm1628_segment {
+	u32 grid;
+	u32 seg;
+};
+
+struct tm1628_display {
+	struct tm1628_segment segments[8];
+};
+
 struct tm1628_led {
 	struct led_classdev	leddev;
 	struct tm1628		*ctrl;
@@ -62,6 +71,8 @@  struct tm1628 {
 	int				mode_index;
 	int				pwm_index;
 	u8				data[14];
+	unsigned int			num_displays;
+	struct tm1628_display		*displays;
 	unsigned int			num_leds;
 	struct tm1628_led		leds[];
 };
@@ -253,6 +264,215 @@  static int tm1628_register_led(struct tm1628 *s,
 	return devm_led_classdev_register_ext(dev, &led->leddev, &init_data);
 }
 
+#define SSD_TOP			BIT(0)
+#define SSD_TOP_RIGHT		BIT(1)
+#define SSD_BOTTOM_RIGHT	BIT(2)
+#define SSD_BOTTOM		BIT(3)
+#define SSD_BOTTOM_LEFT		BIT(4)
+#define SSD_TOP_LEFT		BIT(5)
+#define SSD_MIDDLE		BIT(6)
+#define SSD_DOT			BIT(7)
+
+struct tm1628_ssd_char {
+	char ch;
+	u8 segs;
+};
+
+static const struct tm1628_ssd_char tm1628_char_ssd_map[] = {
+	{ '0', SSD_TOP | SSD_TOP_LEFT | SSD_TOP_RIGHT |
+	       SSD_BOTTOM_LEFT | SSD_BOTTOM_RIGHT | SSD_BOTTOM },
+	{ '1', SSD_TOP_RIGHT | SSD_BOTTOM_RIGHT },
+	{ '2', SSD_TOP | SSD_TOP_RIGHT | SSD_MIDDLE | SSD_BOTTOM_LEFT | SSD_BOTTOM },
+	{ '3', SSD_TOP | SSD_TOP_RIGHT | SSD_MIDDLE | SSD_BOTTOM_RIGHT | SSD_BOTTOM },
+	{ '4', SSD_TOP_LEFT | SSD_TOP_RIGHT | SSD_MIDDLE | SSD_BOTTOM_RIGHT },
+	{ '5', SSD_TOP | SSD_TOP_LEFT | SSD_MIDDLE | SSD_BOTTOM_RIGHT | SSD_BOTTOM },
+	{ '6', SSD_TOP | SSD_TOP_LEFT | SSD_MIDDLE | SSD_BOTTOM_LEFT | SSD_BOTTOM_RIGHT | SSD_BOTTOM },
+	{ '7', SSD_TOP | SSD_TOP_RIGHT | SSD_BOTTOM_RIGHT },
+	{ '8', SSD_TOP | SSD_TOP_LEFT | SSD_TOP_RIGHT | SSD_MIDDLE |
+	       SSD_BOTTOM_LEFT | SSD_BOTTOM_RIGHT | SSD_BOTTOM },
+	{ '9', SSD_TOP | SSD_TOP_LEFT | SSD_TOP_RIGHT | SSD_MIDDLE |
+	       SSD_BOTTOM_RIGHT | SSD_BOTTOM },
+	{ 'A', SSD_TOP | SSD_TOP_LEFT | SSD_TOP_RIGHT | SSD_MIDDLE |
+	       SSD_BOTTOM_LEFT | SSD_BOTTOM_RIGHT },
+	{ 'B', SSD_TOP | SSD_TOP_LEFT | SSD_TOP_RIGHT | SSD_MIDDLE |
+	       SSD_BOTTOM_LEFT | SSD_BOTTOM_RIGHT | SSD_BOTTOM },
+	{ 'C', SSD_TOP | SSD_TOP_LEFT | SSD_BOTTOM_LEFT | SSD_BOTTOM },
+	{ 'D', SSD_TOP | SSD_TOP_LEFT | SSD_TOP_RIGHT |
+	       SSD_BOTTOM_LEFT | SSD_BOTTOM_RIGHT | SSD_BOTTOM },
+	{ 'E', SSD_TOP | SSD_TOP_LEFT | SSD_MIDDLE | SSD_BOTTOM_LEFT | SSD_BOTTOM },
+	{ 'F', SSD_TOP | SSD_TOP_LEFT | SSD_MIDDLE | SSD_BOTTOM_LEFT },
+	{ 'G', SSD_TOP | SSD_TOP_LEFT | SSD_BOTTOM_LEFT | SSD_BOTTOM | SSD_BOTTOM_RIGHT },
+	{ 'H', SSD_TOP_LEFT | SSD_TOP_RIGHT | SSD_MIDDLE |
+	       SSD_BOTTOM_LEFT | SSD_BOTTOM_RIGHT },
+	{ 'I', SSD_TOP_LEFT | SSD_BOTTOM_LEFT },
+	{ 'J', SSD_TOP | SSD_TOP_RIGHT | SSD_BOTTOM_RIGHT | SSD_BOTTOM },
+	{ 'K', SSD_TOP_LEFT | SSD_TOP_RIGHT | SSD_MIDDLE |
+	       SSD_BOTTOM_LEFT | SSD_BOTTOM_RIGHT },
+	{ 'L', SSD_TOP_LEFT | SSD_BOTTOM_LEFT | SSD_BOTTOM },
+	{ 'O', SSD_TOP | SSD_TOP_LEFT | SSD_TOP_RIGHT |
+	       SSD_BOTTOM_LEFT | SSD_BOTTOM_RIGHT | SSD_BOTTOM },
+	{ 'P', SSD_TOP | SSD_TOP_LEFT | SSD_TOP_RIGHT | SSD_MIDDLE |
+	       SSD_BOTTOM_LEFT },
+	{ 'Q', SSD_TOP | SSD_TOP_LEFT | SSD_TOP_RIGHT |
+	       SSD_BOTTOM_LEFT | SSD_BOTTOM_RIGHT | SSD_BOTTOM },
+	{ 'R', SSD_TOP | SSD_TOP_LEFT | SSD_TOP_RIGHT | SSD_MIDDLE |
+	       SSD_BOTTOM_LEFT | SSD_BOTTOM_RIGHT },
+	{ 'S', SSD_TOP | SSD_TOP_LEFT | SSD_MIDDLE | SSD_BOTTOM_RIGHT | SSD_BOTTOM },
+	{ 'T', SSD_TOP | SSD_TOP_LEFT | SSD_BOTTOM_LEFT },
+	{ 'U', SSD_TOP_LEFT | SSD_BOTTOM_LEFT | SSD_BOTTOM | SSD_BOTTOM_RIGHT | SSD_TOP_RIGHT },
+	{ 'V', SSD_TOP_LEFT | SSD_BOTTOM_LEFT | SSD_BOTTOM | SSD_BOTTOM_RIGHT | SSD_TOP_RIGHT },
+	{ 'W', SSD_TOP_LEFT | SSD_BOTTOM_LEFT | SSD_BOTTOM | SSD_BOTTOM_RIGHT | SSD_TOP_RIGHT },
+	{ 'Z', SSD_TOP | SSD_TOP_RIGHT | SSD_MIDDLE | SSD_BOTTOM_LEFT | SSD_BOTTOM },
+	{ 'b', SSD_TOP_LEFT | SSD_MIDDLE | SSD_BOTTOM_LEFT | SSD_BOTTOM | SSD_BOTTOM_RIGHT },
+	{ 'l', SSD_TOP_LEFT | SSD_BOTTOM_LEFT },
+	{ 'o', SSD_MIDDLE | SSD_BOTTOM_LEFT | SSD_BOTTOM | SSD_BOTTOM_RIGHT },
+	{ 't', SSD_TOP_LEFT | SSD_MIDDLE | SSD_BOTTOM_LEFT | SSD_BOTTOM },
+	{ 'u', SSD_BOTTOM_LEFT | SSD_BOTTOM | SSD_BOTTOM_RIGHT },
+	{ 'v', SSD_BOTTOM_LEFT | SSD_BOTTOM | SSD_BOTTOM_RIGHT },
+	{ 'w', SSD_BOTTOM_LEFT | SSD_BOTTOM | SSD_BOTTOM_RIGHT },
+	{ '-', SSD_MIDDLE },
+	{ '_', SSD_BOTTOM },
+	{ '.', SSD_DOT },
+};
+
+static u8 tm1628_get_char_ssd_map(char ch)
+{
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(tm1628_char_ssd_map); i++) {
+		if (tm1628_char_ssd_map[i].ch == ch)
+			return tm1628_char_ssd_map[i].segs;
+	}
+
+	return 0x0;
+}
+
+static int tm1628_display_apply_map(struct tm1628 *s,
+	struct tm1628_display *display, u8 map)
+{
+	struct tm1628_segment *segment;
+	int i;
+
+	for (i = 0; i < 8; i++) {
+		segment = &display->segments[i];
+		tm1628_set_led(s, segment->grid, segment->seg, map & BIT(i));
+	}
+
+	return 0;
+}
+
+static ssize_t text_store(struct device *dev,
+	struct device_attribute *attr, const char *buf, size_t count)
+{
+	struct tm1628 *s = dev_get_drvdata(dev);
+	size_t offset, len = count;
+	u8 map;
+	int i, ret;
+
+	if (len > 0 && buf[len - 1] == '\n')
+		len--;
+
+	for (i = 0, offset = 0; i < s->num_displays; i++) {
+		if (offset < len) {
+			map = tm1628_get_char_ssd_map(buf[offset]);
+			offset++;
+		} else
+			map = 0x0;
+
+		tm1628_display_apply_map(s, &s->displays[i], map);
+	}
+
+	ret = tm1628_set_address(s->spi, 0x0);
+	if (ret)
+		return ret;
+
+	ret = tm1628_write_data(s->spi, s->data, 14);
+	if (ret)
+		return ret;
+
+	return count;
+}
+
+static struct device_attribute tm1628_attr =
+	__ATTR_WO(text);
+
+static int tm1628_register_display(struct tm1628 *s,
+	struct fwnode_handle *node)
+{
+	struct device *dev = &s->spi->dev;
+	struct tm1628_display *display;
+	u32 *reg;
+	u32 grid, seg;
+	int i, j, ret, reg_count;
+
+	reg_count = fwnode_property_count_u32(node, "reg");
+	if (reg_count < 0)
+		return reg_count;
+
+	if (reg_count % 2) {
+		dev_warn(dev, "Ignoring extra cell in %s reg property\n",
+			 fwnode_get_name(node));
+		reg_count--;
+	}
+
+	if (s->displays) {
+		dev_warn(dev, "Only one display supported\n");
+		return -EINVAL;
+	}
+
+	s->num_displays = reg_count >> 1;
+
+	reg = devm_kzalloc(dev, reg_count * sizeof(*reg), GFP_KERNEL);
+	if (!reg)
+		return -ENOMEM;
+
+	ret = fwnode_property_read_u32_array(node, "reg", reg, reg_count);
+	if (ret) {
+		dev_err(dev, "Reading %s reg property failed (%d)\n",
+			fwnode_get_name(node), ret);
+		return ret;
+	}
+
+	s->displays = devm_kzalloc(dev, s->num_displays * sizeof(*s->displays), GFP_KERNEL);
+	if (!s->displays)
+		return -ENOMEM;
+
+	for (i = 0; i < s->num_displays; i++) {
+		display = &s->displays[i];
+		grid = reg[i * 2];
+		seg  = reg[i * 2 + 1];
+		if (grid == 0 && seg != 0) {
+			if (!tm1628_is_valid_seg(s, seg)) {
+				dev_warn(dev, "%s reg out of range\n", fwnode_get_name(node));
+				return -EINVAL;
+			}
+			grid = s->info->modes[s->mode_index].grid_mask;
+			for (j = 0; grid && j < 7; j++) {
+				display->segments[j].seg = seg;
+				display->segments[j].grid = __ffs(grid);
+				grid &= ~BIT(display->segments[j].grid);
+			}
+		} else if (grid != 0 && seg == 0) {
+			if (!tm1628_is_valid_grid(s, grid)) {
+				dev_warn(dev, "%s reg out of range\n", fwnode_get_name(node));
+				return -EINVAL;
+			}
+			seg = s->info->modes[s->mode_index].seg_mask;
+			for (j = 0; seg && j < 8; j++) {
+				display->segments[j].grid = grid;
+				display->segments[j].seg = __ffs(seg);
+				seg &= ~BIT(display->segments[j].seg);
+			}
+		}
+	}
+
+	devm_kfree(dev, reg);
+
+	device_create_file(dev, &tm1628_attr);
+
+	return 0;
+}
+
 /* Work around __builtin_popcount() */
 static u32 tm1628_grid_popcount(u8 grid_mask)
 {
@@ -325,7 +545,7 @@  static int tm1628_spi_probe(struct spi_device *spi)
 			return ret;
 		}
 
-		if (fwnode_property_count_u32(child, "reg") == 2) {
+		if (reg[0] != 0 && reg[1] != 0 && fwnode_property_count_u32(child, "reg") == 2) {
 			ret = tm1628_register_led(s, child, reg[0], reg[1], &s->leds[i++]);
 			if (ret && ret != -EINVAL) {
 				dev_err(&spi->dev, "Failed to register LED %s (%d)\n",
@@ -334,6 +554,14 @@  static int tm1628_spi_probe(struct spi_device *spi)
 				return ret;
 			}
 			s->num_leds++;
+		} else {
+			ret = tm1628_register_display(s, child);
+			if (ret) {
+				dev_err(&spi->dev, "Failed to register display %s (%d)\n",
+					fwnode_get_name(child), ret);
+				fwnode_handle_put(child);
+				return ret;
+			}
 		}
 	}