V4L/DVB (9584): Support different GPIO/GPO registers for newer devices

Empia moved the location of the GPIO/GPO registers in newer devices.  Add the
ability to specify the relocated registers (including caching of register
contents).

Thanks for Ray Lu from Empia for providing the em2874 datasheet.
Signed-off-by: Devin Heitmueller <devin.heitmueller@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

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

@@ -1312,11 +1312,13 @@ void em28xx_pre_card_setup(struct em28xx *dev)
 {
 	int rc;
 
-	rc = em28xx_read_reg(dev, EM2880_R04_GPO);
-	if (rc >= 0)
-		dev->reg_gpo = rc;
+	/* Set the default GPO/GPIO for legacy devices */
+	dev->reg_gpo_num = EM2880_R04_GPO;
+	dev->reg_gpio_num = EM28XX_R08_GPIO;
 
 	dev->wait_after_write = 5;
+
+	/* Based on the Chip ID, set the device configuration */
 	rc = em28xx_read_reg(dev, EM28XX_R0A_CHIPID);
 	if (rc > 0) {
 		dev->chip_id = rc;
@@ -1326,6 +1328,7 @@ void em28xx_pre_card_setup(struct em28xx *dev)
 			break;
 		case CHIP_ID_EM2874:
 			em28xx_info("chip ID is em2874\n");
+			dev->reg_gpio_num = EM2874_R80_GPIO;
 			dev->wait_after_write = 0;
 			break;
 		case CHIP_ID_EM2883:
@@ -1336,6 +1339,12 @@ void em28xx_pre_card_setup(struct em28xx *dev)
 			em28xx_info("em28xx chip ID = %d\n", rc);
 		}
 	}
+
+	/* Prepopulate cached GPO register content */
+	rc = em28xx_read_reg(dev, dev->reg_gpo_num);
+	if (rc >= 0)
+		dev->reg_gpo = rc;
+
 	em28xx_set_model(dev);
 
 	/* request some modules */

drivers/media/video/em28xx/em28xx-core.c

@@ -187,9 +187,9 @@ int em28xx_write_regs(struct em28xx *dev, u16 reg, char *buf, int len)
 	   Not sure what happens on reading GPO register.
 	 */
 	if (rc >= 0) {
-		if (reg == EM2880_R04_GPO)
+		if (reg == dev->reg_gpo_num)
 			dev->reg_gpo = buf[0];
-		else if (reg == EM28XX_R08_GPIO)
+		else if (reg == dev->reg_gpio_num)
 			dev->reg_gpio = buf[0];
 	}
 
@@ -208,9 +208,9 @@ static int em28xx_write_reg_bits(struct em28xx *dev, u16 reg, u8 val,
 	u8 newval;
 
 	/* Uses cache for gpo/gpio registers */
-	if (reg == EM2880_R04_GPO)
+	if (reg == dev->reg_gpo_num)
 		oldval = dev->reg_gpo;
-	else if (reg == EM28XX_R08_GPIO)
+	else if (reg == dev->reg_gpio_num)
 		oldval = dev->reg_gpio;
 	else
 		oldval = em28xx_read_reg(dev, reg);

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

@@ -76,6 +76,9 @@
 #define EM28XX_R10_LINE_IN_AC97    0x10
 #define EM28XX_R14_VIDEO_AC97	0x14
 
+/* em2874 registers */
+#define EM2874_R80_GPIO         0x80
+
 /* register settings */
 #define EM2800_AUDIO_SRC_TUNER  0x0d
 #define EM2800_AUDIO_SRC_LINE   0x0c

drivers/media/video/em28xx/em28xx.h

@@ -471,6 +471,9 @@ struct em28xx {
 
 	enum em28xx_mode mode;
 
+	/* register numbers for GPO/GPIO registers */
+	u16 reg_gpo_num, reg_gpio_num;
+
 	/* Caches GPO and GPIO registers */
 	unsigned char	reg_gpo, reg_gpio;