[media] cx24120: i2c-max-write-size is now configurable

Some i2c-hosts are quite limited regarding maximum
i2c-burst-write-sizes. This patch makes the previously
hardcoded field configurable by users of the driver.
Signed-off-by: Patrick Boettcher <patrick.boettcher@posteo.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

drivers/media/common/b2c2/flexcop-fe-tuner.c

@@ -630,6 +630,7 @@ static const struct cx24120_config skystar2_rev3_3_cx24120_config = {
 	.xtal_khz = 10111,
 	.initial_mpeg_config = { 0xa1, 0x76, 0x07 },
 	.request_firmware = flexcop_fe_request_firmware,
+	.i2c_wr_max = 4,
 };
 
 static int skystarS2_rev33_attach(struct flexcop_device *fc,

drivers/media/dvb-frontends/cx24120.c

@@ -209,24 +209,28 @@ static int cx24120_writereg(struct cx24120_state *state, u8 reg, u8 data)
 }
 
 
-/* Write multiple registers */
+/* Write multiple registers in chunks of i2c_wr_max-sized buffers */
 static int cx24120_writeregN(struct cx24120_state *state,
 			u8 reg, const u8 *values, u16 len, u8 incr)
 {
 	int ret;
-	u8 buf[5]; /* maximum 4 data bytes at once - flexcop limitation
-			(very limited i2c-interface this one) */
+	u16 max = state->config->i2c_wr_max > 0 ?
+				state->config->i2c_wr_max :
+				len;
 
 	struct i2c_msg msg = {
 		.addr = state->config->i2c_addr,
 		.flags = 0,
-		.buf = buf,
-		.len = len };
+	};
+
+	msg.buf = kmalloc(max + 1, GFP_KERNEL);
+	if (msg.buf == NULL)
+		return -ENOMEM;
 
 	while (len) {
-		buf[0] = reg;
-		msg.len = len > 4 ? 4 : len;
-		memcpy(&buf[1], values, msg.len);
+		msg.buf[0] = reg;
+		msg.len = len > max ? max : len;
+		memcpy(&msg.buf[1], values, msg.len);
 
 		len    -= msg.len;      /* data length revers counter */
 		values += msg.len;      /* incr data pointer */
@@ -238,17 +242,20 @@ static int cx24120_writeregN(struct cx24120_state *state,
 		ret = i2c_transfer(state->i2c, &msg, 1);
 		if (ret != 1) {
 			err("i2c_write error(err == %i, 0x%02x)\n", ret, reg);
-			return ret;
+			goto out;
 		}
 
 		dev_dbg(&state->i2c->dev,
 			"%s: reg=0x%02x; data=0x%02x,0x%02x,0x%02x,0x%02x\n",
 			__func__, reg,
-			buf[1], buf[2], buf[3], buf[4]);
-
+			msg.buf[1], msg.buf[2], msg.buf[3], msg.buf[4]);
 	}
 
-	return 0;
+	ret = 0;
+
+out:
+	kfree(msg.buf);
+	return ret;
 }
 
 
@@ -1434,7 +1441,6 @@ int cx24120_init(struct dvb_frontend *fe)
 	}
 	info("FW version %i.%i.%i.%i\n", vers[0], vers[1], vers[2], vers[3]);
 
-
 	state->cold_init = 1;
 	return 0;
 }

drivers/media/dvb-frontends/cx24120.h

@@ -37,6 +37,9 @@ struct cx24120_config {
 
 	int (*request_firmware)(struct dvb_frontend *fe,
 				const struct firmware **fw, char *name);
+
+	/* max bytes I2C provider can write at once */
+	u16 i2c_wr_max;
 };
 
 #if IS_REACHABLE(CONFIG_DVB_CX24120)