drivers/lcd: Add ioctl to get LCD panel ID by seokhun-eom24 · Pull Request #7103 · Samsung/TizenRT

seokhun-eom24 · 2025-12-29T06:58:13Z

drivers/lcd

Add LCDDEVIO_GETPANELID ioctl command to read 24-bit panel ID.
Implement getpanelid in MIPI LCD driver.
Require CMD mode for panel ID read operation.

examples

Add lcd_get_panelid() to retrieve and display the 24-bit LCD panel ID.
Update show_usage() and main() to support the "panelid" command.

[USAGE]

TASH>>lcd_test panelid
TASH>>LCD Panel ID: 0x010000

anjana348 · 2025-12-29T10:04:56Z

 };

 static struct mipi_lcd_dev_s g_lcdcdev;
+static bool g_panelid_initialized = false;


we can use private struct variable instead of global.?

Or, we can add it into get_lcdinfo.

I modified it to use a member variable of mipi_lcd_dev_s instead of a global variable.
I separated get_lcdinfo and created a separate displayid because lcdinfo uses a static CONFIG value, while displayid dynamically retrieves the ID of the connected display.

ewoodev · 2025-12-29T12:45:54Z

 };

 static struct mipi_lcd_dev_s g_lcdcdev;
+static bool g_panelid_initialized = false;


Or, we can add it into get_lcdinfo.

ewoodev · 2025-12-29T12:47:17Z

+	FAR struct mipi_lcd_dev_s *priv = (FAR struct mipi_lcd_dev_s *)dev;
+	int status;
+	lcd_mode_t original_mode;
+	lcm_setting_table_t read_id_cmd = {0x04, 0, {0x00}};


is This command DSC?
If it is specific command, we can wrapping this command to configure or new lcd sepecific api

Yes it's DSC.
So I tired to implement mipi_dsi_dcs_get_display_id function in mipi_dsi_device.c like below.

int mipi_dsi_dcs_get_display_id(FAR struct mipi_dsi_device *device, FAR uint32_t *displayid) { int ret; uint8_t rxbuf[3]; uint8_t length = sizeof(rxbuf) / sizeof(rxbuf[0]); ret = mipi_dsi_set_maximum_return_packet_size(device, length); if (ret < 0) { return ret; } ret = mipi_dsi_generic_read(device, MIPI_DCS_GET_DISPLAY_ID, 0, rxbuf, length); if (ret < 0) { return ret; } *displayid = (rxbuf[0] << 16) | (rxbuf[1] << 8) | rxbuf[2]; return OK; }

But we have issue with this approach.
In mipi_lcd.c command is stored in msg.channel like msg.channel = cmd;.
In mipi_dsi_device.c command is stored in tx_buf like msg.tx_buf = &cmd;.
In BSP code, we assume cmd is stored in msg.channel and also stored in packet.header[0] use that value in amebasmart_mipi_transfer.
But mipi_dsi_device.c's approach is standard.

So, before we wrapping this command with dcs function like mipi_dsi_dcs_get_display_id, we should refactor mipi_lcd.c and bsp code to follow dcs command format.

pcs1265 · 2026-01-07T06:14:26Z

+			priv->displayid = (rxbuf[0] << 16) | (rxbuf[1] << 8) | rxbuf[2];
+			*displayid = priv->displayid;
+			priv->displayid_initialized = true;
+		}


Is there no chance to fail the function read_response or set_return_packet_len?

Of course, the read_response and set_return_packet_len functions can also fail.
In this case, the if case will not be executed, but the cleanup operation must still be performed in the same way, so no separate else handling was added.

pcs1265 · 2026-01-07T06:26:31Z

 	if (argc == 2) {
 		if (!strncmp(argv[1], "lcdinfo", 8)) {
 			return lcd_get_info();
+		} else if (!strncmp(argv[1], "displayid", 8)) {


Third argument need to be 9.

Suggested change

} else if (!strncmp(argv[1], "displayid", 8)) {

} else if (!strncmp(argv[1], "displayid", 9)) {

Thank you for finding this, as I missed this part while changing the command from panelid to displayid.
I corrected it to 10 (length + 1) for an exact string match.

ewoodev · 2026-02-02T09:32:06Z

 	priv->config = config;
 	priv->power = 0;
 	priv->lcdonoff = LCD_OFF;
+	priv->displayid = 0;


if displayid is used often, it's better to store id to ram.
But, i think, this id is not used often.

So, we don't need to store

I agree with Mr Nam, display id will not be used frequently from ioctl so we might skip storing it and just read it directly from h/w. Do we know which scenario it will be used ?

I updated to not store displayid in RAM.

We support different vendors for LCD. So when we have a hardware issue with an LCD panel, we want to know which vendor’s LCD it is. In this scenario we need to know the displayid.

- Add LCDDEVIO_GETDISPLAYID ioctl command to read 24-bit display ID. - Implement getdisplayid in MIPI LCD driver. - Require CMD mode for display ID read operation. Signed-off-by: seokhun-eom <seokhun.eom@samsung.com>

- Add lcd_get_displayid() to retrieve and display the 24-bit LCD display ID. - Update show_usage() and main() to support the "displayid" command. [USAGE] ``` TASH>>lcd_test displayid TASH>>LCD Panel ID: 0x010000 ``` Signed-off-by: seokhun-eom <seokhun.eom@samsung.com>

ewoodev · 2026-02-04T02:24:00Z

@@ -65,6 +65,7 @@
 #define LCDDEVIO_INIT         _LCDIOC(18)
 #define LCDDEVIO_SETORIENTATION  _LCDIOC(19)    /* Arg: int */
 #define LCDDEVIO_GETLCDINFO    _LCDIOC(20)    /* Arg: struct lcd_info_s* Description: Get the static LCD characteristics such as width, height, size and DPI. */


lcd init is already exist.
how about use it ?

Taejun-Kwon · 2026-02-04T02:42:19Z

 	return ret;
 }

+static int lcd_get_displayid(void)


App should not take care of vendor of LCD, it must be abstracted.
Even if there are some types of LCD, framework & App should not change api of code. otherwise it is not good driver & framework model.
Hence I think you should not remove ioctl, and print out id of lcd when LCD initailized, that is enough.

seokhun-eom24 · 2026-02-13T08:16:00Z

I'll handle this PR after merge #7018

anjana348 reviewed Dec 29, 2025

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ewoodev reviewed Dec 29, 2025

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seokhun-eom24 force-pushed the 251224-lcd-id-ioctl branch 2 times, most recently from ee6b0c4 to 0839329 Compare January 6, 2026 02:03

pcs1265 reviewed Jan 7, 2026

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seokhun-eom24 force-pushed the 251224-lcd-id-ioctl branch from 0839329 to e075c4a Compare January 7, 2026 07:34

ewoodev reviewed Feb 2, 2026

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seokhun-eom24 force-pushed the 251224-lcd-id-ioctl branch 2 times, most recently from 729e131 to 68876c8 Compare February 3, 2026 00:55

seokhun-eom24 added 2 commits February 3, 2026 09:57

drivers/lcd: Add ioctl to get LCD display ID

3d5ae35

- Add LCDDEVIO_GETDISPLAYID ioctl command to read 24-bit display ID. - Implement getdisplayid in MIPI LCD driver. - Require CMD mode for display ID read operation. Signed-off-by: seokhun-eom <seokhun.eom@samsung.com>

seokhun-eom24 force-pushed the 251224-lcd-id-ioctl branch from 68876c8 to b4a3366 Compare February 3, 2026 00:57

ewoodev reviewed Feb 4, 2026

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Taejun-Kwon reviewed Feb 4, 2026

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seokhun-eom24 marked this pull request as draft February 13, 2026 08:15

	} else if (!strncmp(argv[1], "displayid", 8)) {
	} else if (!strncmp(argv[1], "displayid", 9)) {

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seokhun-eom24 commented Feb 13, 2026

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seokhun-eom24 commented Dec 29, 2025 •

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