Re: [PATCH 17/17] auxdisplay: ht16k33: Add segment display LED support

From: Robin van der Gracht
Date: Tue Mar 23 2021 - 06:09:06 EST

On 2021-03-22 15:48, Geert Uytterhoeven wrote:
Instantiate a single LED for a segment display. This allows the user to
control display brightness and blinking through the LED class API and
triggers, and exposes the display color.

Signed-off-by: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
---
For setting display brightness, this could use the existing backlight
support for frame buffer devices instantiated for dot-matrix displays.
However, using the leds subsystem instead has the advantage that the
driver can make use of the HT16K33's hardware blinking support, and can
expose the display color.
---
drivers/auxdisplay/ht16k33.c | 81 ++++++++++++++++++++++++++++++++++--
1 file changed, 77 insertions(+), 4 deletions(-)

diff --git a/drivers/auxdisplay/ht16k33.c b/drivers/auxdisplay/ht16k33.c
index 0b502a6039f89c6b..5821addd9aec5633 100644
--- a/drivers/auxdisplay/ht16k33.c
+++ b/drivers/auxdisplay/ht16k33.c
@@ -29,6 +29,7 @@
#include <asm/unaligned.h>

#include "line-display.h"
+#include "../leds/leds.h" /* for led_colors[] */

/* Registers */
#define REG_SYSTEM_SETUP 0x20
@@ -36,6 +37,10 @@

#define REG_DISPLAY_SETUP 0x80
#define REG_DISPLAY_SETUP_ON BIT(0)
+#define REG_DISPLAY_SETUP_BLINK_OFF (0 << 1)
+#define REG_DISPLAY_SETUP_BLINK_2HZ (1 << 1)
+#define REG_DISPLAY_SETUP_BLINK_1HZ (2 << 1)
+#define REG_DISPLAY_SETUP_BLINK_0HZ5 (3 << 1)

#define REG_ROWINT_SET 0xA0
#define REG_ROWINT_SET_INT_EN BIT(0)
@@ -57,6 +62,8 @@
#define BYTES_PER_ROW (HT16K33_MATRIX_LED_MAX_ROWS / 8)
#define HT16K33_FB_SIZE (HT16K33_MATRIX_LED_MAX_COLS * BYTES_PER_ROW)

+#define COLOR_DEFAULT LED_COLOR_ID_RED
+
enum display_type {
DISP_MATRIX = 0,
DISP_QUAD_7SEG,
@@ -85,6 +92,7 @@ struct ht16k33_fbdev {

struct ht16k33_seg {
struct linedisp linedisp;
+ struct led_classdev led;
union {
struct seg7_conversion_map seg7;
struct seg14_conversion_map seg14;
@@ -102,6 +110,7 @@ struct ht16k33_priv {
struct ht16k33_seg seg;
};
enum display_type type;
+ uint8_t blink;
};

static const struct fb_fix_screeninfo ht16k33_fb_fix = {
@@ -160,7 +169,7 @@ static DEVICE_ATTR(map_seg14, 0644, map_seg_show,
map_seg_store);

static int ht16k33_display_on(struct ht16k33_priv *priv)
{
- uint8_t data = REG_DISPLAY_SETUP | REG_DISPLAY_SETUP_ON;
+ uint8_t data = REG_DISPLAY_SETUP | REG_DISPLAY_SETUP_ON | priv->blink;

return i2c_smbus_write_byte(priv->client, data);
}
@@ -175,8 +184,11 @@ static int ht16k33_brightness_set(struct
ht16k33_priv *priv,
{
int error;

- if (brightness == 0)
+ if (brightness == 0) {
+ // Disable blink mode
+ priv->blink = REG_DISPLAY_SETUP_BLINK_OFF;
return ht16k33_display_off(priv);
+ }

error = ht16k33_display_on(priv);
if (error)
@@ -186,6 +198,49 @@ static int ht16k33_brightness_set(struct
ht16k33_priv *priv,
REG_BRIGHTNESS | (brightness - 1));
}

+static int ht16k33_brightness_set_blocking(struct led_classdev *led_cdev,
+ enum led_brightness brightness)
+{
+ struct ht16k33_priv *priv = container_of(led_cdev, struct ht16k33_priv,
+ seg.led);
+
+ return ht16k33_brightness_set(priv, brightness);
+}
+
+static int ht16k33_blink_set(struct led_classdev *led_cdev,
+ unsigned long *delay_on, unsigned long *delay_off)
+{
+ struct ht16k33_priv *priv = container_of(led_cdev, struct ht16k33_priv,
+ seg.led);
+ unsigned int delay;
+ uint8_t blink;
+ int error;
+
+ if (!*delay_on && !*delay_off) {
+ blink = REG_DISPLAY_SETUP_BLINK_1HZ;
+ delay = 1000;
+ } else if (*delay_on <= 750) {
+ blink = REG_DISPLAY_SETUP_BLINK_2HZ;
+ delay = 500;
+ } else if (*delay_on <= 1500) {
+ blink = REG_DISPLAY_SETUP_BLINK_1HZ;
+ delay = 1000;
+ } else {
+ blink = REG_DISPLAY_SETUP_BLINK_0HZ5;
+ delay = 2000;
+ }
+
+ error = i2c_smbus_write_byte(priv->client,
+ REG_DISPLAY_SETUP | REG_DISPLAY_SETUP_ON |
+ blink);
+ if (error)
+ return error;
+
+ priv->blink = blink;
+ *delay_on = *delay_off = delay;
+ return 0;
+}
+
static void ht16k33_fb_queue(struct ht16k33_priv *priv)
{
struct ht16k33_fbdev *fbdev = &priv->fbdev;
@@ -578,11 +633,29 @@ static int ht16k33_fbdev_probe(struct i2c_client *client,
static int ht16k33_seg_probe(struct i2c_client *client,
struct ht16k33_priv *priv, uint32_t brightness)
{
- struct ht16k33_seg *seg = &priv->seg;
struct device *dev = &client->dev;
+ struct device_node *node = dev->of_node;
+ struct ht16k33_seg *seg = &priv->seg;
+ u32 color = COLOR_DEFAULT;
int err;

- err = ht16k33_brightness_set(priv, MAX_BRIGHTNESS);
+ of_property_read_u32(node, "color", &color);
+ seg->led.name = devm_kasprintf(dev, GFP_KERNEL,
+ DRIVER_NAME ":%s:" LED_FUNCTION_BACKLIGHT,
+ color < LED_COLOR_ID_MAX ? led_colors[color] : "");
+ seg->led.brightness_set_blocking = ht16k33_brightness_set_blocking;
+ seg->led.blink_set = ht16k33_blink_set;
+ seg->led.flags = LED_CORE_SUSPENDRESUME;
+ seg->led.brightness = brightness;
+ seg->led.max_brightness = MAX_BRIGHTNESS;
+
+ err = devm_led_classdev_register(dev, &seg->led);
+ if (err) {
+ dev_err(dev, "Failed to register LED\n");
+ return err;
+ }
+
+ err = ht16k33_brightness_set(priv, seg->led.brightness);
if (err)
return err;

The LED class can pretty much do what the backlight class can and more.

Maybe we can stop registering a backlight device in the fbdev case and
register a led device for both. This makes the code cleaner and drops
a dependency but will break backwards compatibility.

I'd prefer a single solution that covers both use cases, but I'm not
sure about the 'breaking backwards compatibility' consequence...

Groetjes / Kind regards,
Robin van der Gracht