media: em28xx: Add StarTech SVID2USB232

Add support for the StarTech SVID2USB232 USB analog video grabber
(USB ID eb1a:8286). The device uses the Empia EM28281 bridge, a
member of the em2828X family with an integrated video decoder.

Reuses the EM28XX_BUILTIN decoder path introduced in commit
8e53399c63 ("media: em28xx: Add support for Empia em2828X bridge").
The standard PAL/NTSC switching and composite/S-Video input
switching in em2828X_decoder_set_std() handle this board without
board-specific code.

Inputs:
 - Composite video
 - S-Video
 - Analog stereo audio (line in)

Tested on hardware with a PAL signal on both S-Video and composite
inputs (ffplay -f v4l2 /dev/video0).

This supersedes an earlier RFC posting from before EM28XX_BUILTIN was
available, which proposed a custom EM28XX_I2C_ALGO_EM28281_INTEGRATED
TVP5150-bridge algorithm. That approach is no longer necessary now that
the em2828X bridge support landed.

Link: https://lore.kernel.org/all/20260119185921.575666-1-xeeynamo@hotmail.com/
Signed-off-by: Luciano Ciccariello <xeeynamo@hotmail.com>
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>

Documentation/admin-guide/media/em28xx-cardlist.rst

@@ -446,3 +446,7 @@ EM28xx cards list
      - MyGica UTV3 Analog USB2.0 TV Box
      - em2860
      - eb1a:2860
+   * - 113
+     - StarTech SVID2USB232
+     - em28281
+     - eb1a:8286

drivers/media/usb/em28xx/em28xx-cards.c

@@ -2677,6 +2677,28 @@ const struct em28xx_board em28xx_boards[] = {
 			.gpio     = mygica_utv3_tuner_audio_gpio,
 		} },
 	},
+	/* eb1a:8286 StarTech SVID2USB232
+	 * Empia EM28281 with integrated TVP5150-compatible video decoder.
+	 * Composite and S-Video inputs, stereo line-in audio.
+	 */
+	[EM28281_BOARD_STARTECH_SVID2USB232] = {
+		.name         = "StarTech SVID2USB232",
+		.vchannels    = 2,
+		.tuner_type   = TUNER_ABSENT,
+		.has_dvb      = 0,
+		.decoder      = EM28XX_BUILTIN,
+		.i2c_speed    = EM28XX_I2C_CLK_WAIT_ENABLE | EM28XX_I2C_FREQ_400_KHZ,
+		.xclk         = EM28XX_XCLK_FREQUENCY_12MHZ,
+		.input           = { {
+			.type     = EM28XX_VMUX_COMPOSITE,
+			.vmux     = EM2828X_COMPOSITE,
+			.amux     = EM28XX_AMUX_LINE_IN,
+		}, {
+			.type     = EM28XX_VMUX_SVIDEO,
+			.vmux     = EM2828X_SVIDEO,
+			.amux     = EM28XX_AMUX_LINE_IN,
+		} },
+	},
 	[EM2828X_BOARD_HAUPPAUGE_USB_LIVE2] = {
 		.name         = "Hauppauge USB Live2",
 		.vchannels    = 2,
@@ -2946,6 +2968,8 @@ struct usb_device_id em28xx_id_table[] = {
 			.driver_info = EM2874_BOARD_HAUPPAUGE_USB_QUADHD },
 	{ USB_DEVICE(0x2040, 0xc220),
 			.driver_info = EM2828X_BOARD_HAUPPAUGE_USB_LIVE2 },
+	{ USB_DEVICE(0xeb1a, 0x8286),
+			.driver_info = EM28281_BOARD_STARTECH_SVID2USB232 },
 	{ USB_DEVICE(0x2040, 0x0360),
 			.driver_info = EM2828X_BOARD_HAUPPAUGE_935_V2 },
 	{ USB_DEVICE(0x2040, 0x8360),
@@ -3859,6 +3883,11 @@ static int em28xx_init_dev(struct em28xx *dev, struct usb_device *udev,
 			dev->wait_after_write = 0;
 			dev->eeprom_addrwidth_16bit = 1;
 			break;
+		case CHIP_ID_EM28281:
+			chip_name = "em28281";
+			dev->wait_after_write = 0;
+			dev->eeprom_addrwidth_16bit = 1;
+			break;
 		case CHIP_ID_EM2883:
 			chip_name = "em2882/3";
 			dev->wait_after_write = 0;

drivers/media/usb/em28xx/em28xx-reg.h

@@ -283,6 +283,7 @@ enum em28xx_chip_id {
 	CHIP_ID_EM2884 = 68,
 	CHIP_ID_EM28174 = 113,
 	CHIP_ID_EM28178 = 114,
+	CHIP_ID_EM28281 = 145,
 	CHIP_ID_EM2828X = 148,
 };
 

drivers/media/usb/em28xx/em28xx.h

@@ -149,6 +149,7 @@
 #define EM2828X_BOARD_HAUPPAUGE_955_V2            110
 #define EM2828X_BOARD_HAUPPAUGE_975_V2            111
 #define EM28178_BOARD_PCTV_461E_V3                112
+#define EM28281_BOARD_STARTECH_SVID2USB232        113
 
 /* Limits minimum and default number of buffers */
 #define EM28XX_MIN_BUF 4