[media] em28xx: remove GPIO register caching

The GPIO register caching is the result of wrong assumptions and incomplete
knowledge about the GPIO registers and their functionality.
Today, we know that it is not needed.
It is also limited to a single register and therefore incomplete (newer chips
are using multiple registers).
Instead of extending the caching, get rid of it, because it has no real
benefits and just bloats/complicates the code.

Signed-off-by: Frank Schäfer <[e-mail]>
Signed-off-by: Mauro Carvalho Chehab <[e-mail]>

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

···
 
 	em28xx_set_model(dev);
 
-	/* Set the default GPO/GPIO for legacy devices */
-	dev->reg_gpo_num = EM2880_R04_GPO;
-	dev->reg_gpio_num = EM2820_R08_GPIO_CTRL;
-
 	dev->wait_after_write = 5;
 
 	/* Based on the Chip ID, set the device configuration */
···
 			break;
 		case CHIP_ID_EM2874:
 			chip_name = "em2874";
-			dev->reg_gpio_num = EM2874_R80_GPIO_P0_CTRL;
 			dev->wait_after_write = 0;
 			dev->eeprom_addrwidth_16bit = 1;
 			break;
 		case CHIP_ID_EM28174:
 			chip_name = "em28174";
-			dev->reg_gpio_num = EM2874_R80_GPIO_P0_CTRL;
 			dev->wait_after_write = 0;
 			dev->eeprom_addrwidth_16bit = 1;
 			break;
···
 			break;
 		case CHIP_ID_EM2884:
 			chip_name = "em2884";
-			dev->reg_gpio_num = EM2874_R80_GPIO_P0_CTRL;
 			dev->wait_after_write = 0;
 			dev->eeprom_addrwidth_16bit = 1;
 			break;
···
 
 		return 0;
 	}
-
-	/* Prepopulate cached GPO register content */
-	retval = em28xx_read_reg(dev, dev->reg_gpo_num);
-	if (retval >= 0)
-		dev->reg_gpo = retval;
 
 	em28xx_pre_card_setup(dev);
 

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

···
 
 int em28xx_write_regs(struct em28xx *dev, u16 reg, char *buf, int len)
 {
-	int rc;
-
-	rc = em28xx_write_regs_req(dev, USB_REQ_GET_STATUS, reg, buf, len);
-
-	/* Stores GPO/GPIO values at the cache, if changed
-	   Only write values should be stored, since input on a GPIO
-	   register will return the input bits.
-	   Not sure what happens on reading GPO register.
-	 */
-	if (rc >= 0) {
-		if (reg == dev->reg_gpo_num)
-			dev->reg_gpo = buf[0];
-		else if (reg == dev->reg_gpio_num)
-			dev->reg_gpio = buf[0];
-	}
-
-	return rc;
+	return em28xx_write_regs_req(dev, USB_REQ_GET_STATUS, reg, buf, len);
 }
 EXPORT_SYMBOL_GPL(em28xx_write_regs);
 
···
 	int oldval;
 	u8 newval;
 
-	/* Uses cache for gpo/gpio registers */
-	if (reg == dev->reg_gpo_num)
-		oldval = dev->reg_gpo;
-	else if (reg == dev->reg_gpio_num)
-		oldval = dev->reg_gpio;
-	else
-		oldval = em28xx_read_reg(dev, reg);
-
+	oldval = em28xx_read_reg(dev, reg);
 	if (oldval < 0)
 		return oldval;
 

drivers/media/usb/em28xx/em28xx.h

···
 
 	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;
-
 	/* Snapshot button */
 	char snapshot_button_path[30];	/* path of the input dev */
 	struct input_dev *sbutton_input_dev;