[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>

3 files changed, 26 insertions, 16 deletions

diff --git a/drivers/media/common/b2c2/flexcop-fe-tuner.c b/drivers/media/common/b2c2/flexcop-fe-tuner.c
index 66f6910a1810..9305266d0ac0 100644
--- a/drivers/media/common/b2c2/flexcop-fe-tuner.c
+++ b/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,
diff --git a/drivers/media/dvb-frontends/cx24120.c b/drivers/media/dvb-frontends/cx24120.c
index ff7f21496186..2ed3fbc81e29 100644
--- a/drivers/media/dvb-frontends/cx24120.c
+++ b/drivers/media/dvb-frontends/cx24120.c
@@ -209,46 +209,53 @@ 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 */
+                len    -= msg.len;      /* data length revers counter */
+                values += msg.len;      /* incr data pointer */
 
                 if (incr)
                         reg += msg.len;
-                msg.len++;                      /* don't forget the addr byte */
+                msg.len++;              /* don't forget the addr byte */
 
                 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;
 }
diff --git a/drivers/media/dvb-frontends/cx24120.h b/drivers/media/dvb-frontends/cx24120.h
index 076d2ddb5dde..e5748aaa8418 100644
--- a/drivers/media/dvb-frontends/cx24120.h
+++ b/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)