[media] smiapp: Quirk for sensors that only do 8-bit reads

Some sensors implement only 8-bit read functionality and fail on wider
reads. Add a quirk flag for such sensors.
Signed-off-by: Sakari Ailus <sakari.ailus@maxwell.research.nokia.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/video/smiapp/smiapp-quirk.h

@@ -46,6 +46,7 @@ struct smiapp_quirk {
 
 /* op pix clock is for all lanes in total normally */
 #define SMIAPP_QUIRK_FLAG_OP_PIX_CLOCK_PER_LANE			(1 << 0)
+#define SMIAPP_QUIRK_FLAG_8BIT_READ_ONLY			(1 << 1)
 
 struct smiapp_reg_8 {
 	u16 reg;

drivers/media/video/smiapp/smiapp-regs.c

@@ -78,19 +78,15 @@ static uint32_t float_to_u32_mul_1000000(struct i2c_client *client,
  * Read a 8/16/32-bit i2c register.  The value is returned in 'val'.
  * Returns zero if successful, or non-zero otherwise.
  */
-int smiapp_read(struct smiapp_sensor *sensor, u32 reg, u32 *val)
+static int ____smiapp_read(struct smiapp_sensor *sensor, u16 reg,
+			   u16 len, u32 *val)
 {
 	struct i2c_client *client = v4l2_get_subdevdata(&sensor->src->sd);
 	struct i2c_msg msg;
 	unsigned char data[4];
-	unsigned int len = (u8)(reg >> 16);
 	u16 offset = reg;
 	int r;
 
-	if (len != SMIA_REG_8BIT && len != SMIA_REG_16BIT
-	    && len != SMIA_REG_32BIT)
-		return -EINVAL;
-
 	msg.addr = client->addr;
 	msg.flags = 0;
 	msg.len = 2;
@@ -132,9 +128,6 @@ int smiapp_read(struct smiapp_sensor *sensor, u32 reg, u32 *val)
 		BUG();
 	}
 
-	if (reg & SMIA_REG_FLAG_FLOAT)
-		*val = float_to_u32_mul_1000000(client, *val);
-
 	return 0;
 
 err:
@@ -143,6 +136,68 @@ int smiapp_read(struct smiapp_sensor *sensor, u32 reg, u32 *val)
 	return r;
 }
 
+/* Read a register using 8-bit access only. */
+static int ____smiapp_read_8only(struct smiapp_sensor *sensor, u16 reg,
+				 u16 len, u32 *val)
+{
+	unsigned int i;
+	int rval;
+
+	*val = 0;
+
+	for (i = 0; i < len; i++) {
+		u32 val8;
+
+		rval = ____smiapp_read(sensor, reg + i, 1, &val8);
+		if (rval < 0)
+			return rval;
+		*val |= val8 << ((len - i - 1) << 3);
+	}
+
+	return 0;
+}
+
+/*
+ * Read a 8/16/32-bit i2c register.  The value is returned in 'val'.
+ * Returns zero if successful, or non-zero otherwise.
+ */
+static int __smiapp_read(struct smiapp_sensor *sensor, u32 reg, u32 *val,
+			 bool only8)
+{
+	struct i2c_client *client = v4l2_get_subdevdata(&sensor->src->sd);
+	unsigned int len = (u8)(reg >> 16);
+	int rval;
+
+	if (len != SMIA_REG_8BIT && len != SMIA_REG_16BIT
+	    && len != SMIA_REG_32BIT)
+		return -EINVAL;
+
+	if (len == SMIA_REG_8BIT && !only8)
+		rval = ____smiapp_read(sensor, (u16)reg, len, val);
+	else
+		rval = ____smiapp_read_8only(sensor, (u16)reg, len, val);
+	if (rval < 0)
+		return rval;
+
+	if (reg & SMIA_REG_FLAG_FLOAT)
+		*val = float_to_u32_mul_1000000(client, *val);
+
+	return 0;
+}
+
+int smiapp_read(struct smiapp_sensor *sensor, u32 reg, u32 *val)
+{
+	return __smiapp_read(
+		sensor, reg, val,
+		smiapp_needs_quirk(sensor,
+				   SMIAPP_QUIRK_FLAG_8BIT_READ_ONLY));
+}
+
+int smiapp_read_8only(struct smiapp_sensor *sensor, u32 reg, u32 *val)
+{
+	return __smiapp_read(sensor, reg, val, true);
+}
+
 /*
  * Write to a 8/16-bit register.
  * Returns zero if successful, or non-zero otherwise.

drivers/media/video/smiapp/smiapp-regs.h

@@ -43,6 +43,7 @@ struct smia_reg {
 struct smiapp_sensor;
 
 int smiapp_read(struct smiapp_sensor *sensor, u32 reg, u32 *val);
+int smiapp_read_8only(struct smiapp_sensor *sensor, u32 reg, u32 *val);
 int smiapp_write(struct smiapp_sensor *sensor, u32 reg, u32 val);
 
 #endif