media: dvb-frontends: fix i2c access helpers for KASAN

A typical code fragment was copied across many dvb-frontend drivers and
causes large stack frames when built with with CONFIG_KASAN on gcc-5/6/7:

drivers/media/dvb-frontends/cxd2841er.c:3225:1: error: the frame size of 3992 bytes is larger than 3072 bytes [-Werror=frame-larger-than=]
drivers/media/dvb-frontends/cxd2841er.c:3404:1: error: the frame size of 3136 bytes is larger than 3072 bytes [-Werror=frame-larger-than=]
drivers/media/dvb-frontends/stv0367.c:3143:1: error: the frame size of 4016 bytes is larger than 3072 bytes [-Werror=frame-larger-than=]
drivers/media/dvb-frontends/stv090x.c:3430:1: error: the frame size of 5312 bytes is larger than 3072 bytes [-Werror=frame-larger-than=]
drivers/media/dvb-frontends/stv090x.c:4248:1: error: the frame size of 4872 bytes is larger than 3072 bytes [-Werror=frame-larger-than=]

gcc-8 now solves this by consolidating the stack slots for the argument
variables, but on older compilers we can get the same behavior by taking
the pointer of a local variable rather than the inline function argument.

Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81715

Cc: stable@vger.kernel.org
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

drivers/media/dvb-frontends/ascot2e.c

@@ -155,7 +155,9 @@ static int ascot2e_write_regs(struct ascot2e_priv *priv,
 
 static int ascot2e_write_reg(struct ascot2e_priv *priv, u8 reg, u8 val)
 {
-	return ascot2e_write_regs(priv, reg, &val, 1);
+	u8 tmp = val; /* see gcc.gnu.org/bugzilla/show_bug.cgi?id=81715 */
+
+	return ascot2e_write_regs(priv, reg, &tmp, 1);
 }
 
 static int ascot2e_read_regs(struct ascot2e_priv *priv,

drivers/media/dvb-frontends/cxd2841er.c

@@ -258,7 +258,9 @@ static int cxd2841er_write_regs(struct cxd2841er_priv *priv,
 static int cxd2841er_write_reg(struct cxd2841er_priv *priv,
 			       u8 addr, u8 reg, u8 val)
 {
-	return cxd2841er_write_regs(priv, addr, reg, &val, 1);
+	u8 tmp = val; /* see gcc.gnu.org/bugzilla/show_bug.cgi?id=81715 */
+
+	return cxd2841er_write_regs(priv, addr, reg, &tmp, 1);
 }
 
 static int cxd2841er_read_regs(struct cxd2841er_priv *priv,

drivers/media/dvb-frontends/helene.c

@@ -331,7 +331,9 @@ static int helene_write_regs(struct helene_priv *priv,
 
 static int helene_write_reg(struct helene_priv *priv, u8 reg, u8 val)
 {
-	return helene_write_regs(priv, reg, &val, 1);
+	u8 tmp = val; /* see gcc.gnu.org/bugzilla/show_bug.cgi?id=81715 */
+
+	return helene_write_regs(priv, reg, &tmp, 1);
 }
 
 static int helene_read_regs(struct helene_priv *priv,

drivers/media/dvb-frontends/horus3a.c

@@ -89,7 +89,9 @@ static int horus3a_write_regs(struct horus3a_priv *priv,
 
 static int horus3a_write_reg(struct horus3a_priv *priv, u8 reg, u8 val)
 {
-	return horus3a_write_regs(priv, reg, &val, 1);
+	u8 tmp = val; /* see gcc.gnu.org/bugzilla/show_bug.cgi?id=81715 */
+
+	return horus3a_write_regs(priv, reg, &tmp, 1);
 }
 
 static int horus3a_enter_power_save(struct horus3a_priv *priv)

drivers/media/dvb-frontends/itd1000.c

@@ -95,8 +95,9 @@ static int itd1000_read_reg(struct itd1000_state *state, u8 reg)
 
 static inline int itd1000_write_reg(struct itd1000_state *state, u8 r, u8 v)
 {
-	int ret = itd1000_write_regs(state, r, &v, 1);
-	state->shadow[r] = v;
+	u8 tmp = v; /* see gcc.gnu.org/bugzilla/show_bug.cgi?id=81715 */
+	int ret = itd1000_write_regs(state, r, &tmp, 1);
+	state->shadow[r] = tmp;
 	return ret;
 }
 

drivers/media/dvb-frontends/mt312.c

@@ -142,7 +142,10 @@ static inline int mt312_readreg(struct mt312_state *state,
 static inline int mt312_writereg(struct mt312_state *state,
 				 const enum mt312_reg_addr reg, const u8 val)
 {
-	return mt312_write(state, reg, &val, 1);
+	u8 tmp = val; /* see gcc.gnu.org/bugzilla/show_bug.cgi?id=81715 */
+
+
+	return mt312_write(state, reg, &tmp, 1);
 }
 
 static inline u32 mt312_div(u32 a, u32 b)

drivers/media/dvb-frontends/stb0899_drv.c

@@ -539,7 +539,8 @@ int stb0899_write_regs(struct stb0899_state *state, unsigned int reg, u8 *data,
 
 int stb0899_write_reg(struct stb0899_state *state, unsigned int reg, u8 data)
 {
-	return stb0899_write_regs(state, reg, &data, 1);
+	u8 tmp = data;
+	return stb0899_write_regs(state, reg, &tmp, 1);
 }
 
 /*

drivers/media/dvb-frontends/stb6100.c

@@ -226,12 +226,14 @@ static int stb6100_write_reg_range(struct stb6100_state *state, u8 buf[], int st
 
 static int stb6100_write_reg(struct stb6100_state *state, u8 reg, u8 data)
 {
+	u8 tmp = data; /* see gcc.gnu.org/bugzilla/show_bug.cgi?id=81715 */
+
 	if (unlikely(reg >= STB6100_NUMREGS)) {
 		dprintk(verbose, FE_ERROR, 1, "Invalid register offset 0x%x", reg);
 		return -EREMOTEIO;
 	}
-	data = (data & stb6100_template[reg].mask) | stb6100_template[reg].set;
-	return stb6100_write_reg_range(state, &data, reg, 1);
+	tmp = (tmp & stb6100_template[reg].mask) | stb6100_template[reg].set;
+	return stb6100_write_reg_range(state, &tmp, reg, 1);
 }
 
 

drivers/media/dvb-frontends/stv0367.c

@@ -166,7 +166,9 @@ int stv0367_writeregs(struct stv0367_state *state, u16 reg, u8 *data, int len)
 
 static int stv0367_writereg(struct stv0367_state *state, u16 reg, u8 data)
 {
-	return stv0367_writeregs(state, reg, &data, 1);
+	u8 tmp = data; /* see gcc.gnu.org/bugzilla/show_bug.cgi?id=81715 */
+
+	return stv0367_writeregs(state, reg, &tmp, 1);
 }
 
 static u8 stv0367_readreg(struct stv0367_state *state, u16 reg)

drivers/media/dvb-frontends/stv090x.c

@@ -755,7 +755,9 @@ static int stv090x_write_regs(struct stv090x_state *state, unsigned int reg, u8
 
 static int stv090x_write_reg(struct stv090x_state *state, unsigned int reg, u8 data)
 {
-	return stv090x_write_regs(state, reg, &data, 1);
+	u8 tmp = data; /* see gcc.gnu.org/bugzilla/show_bug.cgi?id=81715 */
+
+	return stv090x_write_regs(state, reg, &tmp, 1);
 }
 
 static int stv090x_i2c_gate_ctrl(struct stv090x_state *state, int enable)

drivers/media/dvb-frontends/stv6110x.c

@@ -97,7 +97,9 @@ static int stv6110x_write_regs(struct stv6110x_state *stv6110x, int start, u8 da
 
 static int stv6110x_write_reg(struct stv6110x_state *stv6110x, u8 reg, u8 data)
 {
-	return stv6110x_write_regs(stv6110x, reg, &data, 1);
+	u8 tmp = data; /* see gcc.gnu.org/bugzilla/show_bug.cgi?id=81715 */
+
+	return stv6110x_write_regs(stv6110x, reg, &tmp, 1);
 }
 
 static int stv6110x_init(struct dvb_frontend *fe)

drivers/media/dvb-frontends/zl10039.c

@@ -134,7 +134,9 @@ static inline int zl10039_writereg(struct zl10039_state *state,
 				const enum zl10039_reg_addr reg,
 				const u8 val)
 {
-	return zl10039_write(state, reg, &val, 1);
+	const u8 tmp = val; /* see gcc.gnu.org/bugzilla/show_bug.cgi?id=81715 */
+
+	return zl10039_write(state, reg, &tmp, 1);
 }
 
 static int zl10039_init(struct dvb_frontend *fe)