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Message-ID: <543ec200931af3192541fef51bc8e96a@protonic.nl>
Date: Tue, 23 Mar 2021 11:08:15 +0100
From: Robin van der Gracht <robin@...tonic.nl>
To: Geert Uytterhoeven <geert@...ux-m68k.org>
Cc: Rob Herring <robh+dt@...nel.org>, Miguel Ojeda <ojeda@...nel.org>,
Paul Burton <paulburton@...nel.org>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
devicetree@...r.kernel.org, linux-mips@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH 17/17] auxdisplay: ht16k33: Add segment display LED
support
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@...ux-m68k.org>
> ---
> 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
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