Re: [PATCH 20/26] pctv452e: don't do DMA on stack

[Patrick Boettcher <patrick.boettcher@posteo.de>]

On Fri,  7 Oct 2016 14:24:30 -0300
Mauro Carvalho Chehab <mchehab@s-opensource.com> wrote:

> The USB control messages require DMA to work. We cannot pass
> a stack-allocated buffer, as it is not warranted that the
> stack would be into a DMA enabled area.
> 
> Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
> ---
>  drivers/media/usb/dvb-usb/pctv452e.c | 110
> ++++++++++++++++++----------------- 1 file changed, 58 insertions(+),
> 52 deletions(-)
> 
> diff --git a/drivers/media/usb/dvb-usb/pctv452e.c
> b/drivers/media/usb/dvb-usb/pctv452e.c index
> c05de1b088a4..855fe9d34b59 100644 ---
> a/drivers/media/usb/dvb-usb/pctv452e.c +++
> b/drivers/media/usb/dvb-usb/pctv452e.c @@ -97,13 +97,14 @@ struct
> pctv452e_state { u8 c;	   /* transaction counter, wraps
> around...  */ u8 initialized; /* set to 1 if 0x15 has been sent */
>  	u16 last_rc_key;
> +
> +	unsigned char data[80];
>  };
>  
>  static int tt3650_ci_msg(struct dvb_usb_device *d, u8 cmd, u8 *data,
>  			 unsigned int write_len, unsigned int
> read_len) {
>  	struct pctv452e_state *state = (struct pctv452e_state
> *)d->priv;
> -	u8 buf[64];
>  	u8 id;
>  	unsigned int rlen;
>  	int ret;
> @@ -114,30 +115,30 @@ static int tt3650_ci_msg(struct dvb_usb_device
> *d, u8 cmd, u8 *data, 
>  	id = state->c++;
>  
> -	buf[0] = SYNC_BYTE_OUT;
> -	buf[1] = id;
> -	buf[2] = cmd;
> -	buf[3] = write_len;
> +	state->data[0] = SYNC_BYTE_OUT;
> +	state->data[1] = id;
> +	state->data[2] = cmd;
> +	state->data[3] = write_len;
>  
> -	memcpy(buf + 4, data, write_len);
> +	memcpy(state->data + 4, data, write_len);
>  
>  	rlen = (read_len > 0) ? 64 : 0;
> -	ret = dvb_usb_generic_rw(d, buf, 4 + write_len,
> -				  buf, rlen, /* delay_ms */ 0);
> +	ret = dvb_usb_generic_rw(d, state->data, 4 + write_len,
> +				  state->data, rlen, /* delay_ms */
> 0); if (0 != ret)
>  		goto failed;
>  
>  	ret = -EIO;
> -	if (SYNC_BYTE_IN != buf[0] || id != buf[1])
> +	if (SYNC_BYTE_IN != state->data[0] || id != state->data[1])
>  		goto failed;
>  
> -	memcpy(data, buf + 4, read_len);
> +	memcpy(data, state->data + 4, read_len);
>  
>  	return 0;
>  
>  failed:
>  	err("CI error %d; %02X %02X %02X -> %*ph.",
> -	     ret, SYNC_BYTE_OUT, id, cmd, 3, buf);
> +	     ret, SYNC_BYTE_OUT, id, cmd, 3, state->data);
>  
>  	return ret;
>  }
> @@ -405,7 +406,6 @@ static int pctv452e_i2c_msg(struct dvb_usb_device
> *d, u8 addr, u8 *rcv_buf, u8 rcv_len)
>  {
>  	struct pctv452e_state *state = (struct pctv452e_state
> *)d->priv;
> -	u8 buf[64];
>  	u8 id;
>  	int ret;
>  
> @@ -415,42 +415,40 @@ static int pctv452e_i2c_msg(struct
> dvb_usb_device *d, u8 addr, if (snd_len > 64 - 7 || rcv_len > 64 - 7)
>  		goto failed;
>  
> -	buf[0] = SYNC_BYTE_OUT;
> -	buf[1] = id;
> -	buf[2] = PCTV_CMD_I2C;
> -	buf[3] = snd_len + 3;
> -	buf[4] = addr << 1;
> -	buf[5] = snd_len;
> -	buf[6] = rcv_len;
> +	state->data[0] = SYNC_BYTE_OUT;
> +	state->data[1] = id;
> +	state->data[2] = PCTV_CMD_I2C;
> +	state->data[3] = snd_len + 3;
> +	state->data[4] = addr << 1;
> +	state->data[5] = snd_len;
> +	state->data[6] = rcv_len;
>  
> -	memcpy(buf + 7, snd_buf, snd_len);
> +	memcpy(state->data + 7, snd_buf, snd_len);
>  
> -	ret = dvb_usb_generic_rw(d, buf, 7 + snd_len,
> -				  buf, /* rcv_len */ 64,
> +	ret = dvb_usb_generic_rw(d, state->data, 7 + snd_len,
> +				  state->data, /* rcv_len */ 64,
>  				  /* delay_ms */ 0);
>  	if (ret < 0)
>  		goto failed;
>  
>  	/* TT USB protocol error. */
>  	ret = -EIO;
> -	if (SYNC_BYTE_IN != buf[0] || id != buf[1])
> +	if (SYNC_BYTE_IN != state->data[0] || id != state->data[1])
>  		goto failed;
>  
>  	/* I2C device didn't respond as expected. */
>  	ret = -EREMOTEIO;
> -	if (buf[5] < snd_len || buf[6] < rcv_len)
> +	if (state->data[5] < snd_len || state->data[6] < rcv_len)
>  		goto failed;
>  
> -	memcpy(rcv_buf, buf + 7, rcv_len);
> +	memcpy(rcv_buf, state->data + 7, rcv_len);
>  
>  	return rcv_len;
>  
>  failed:
> -	err("I2C error %d; %02X %02X  %02X %02X %02X -> "
> -	     "%02X %02X  %02X %02X %02X.",
> +	err("I2C error %d; %02X %02X  %02X %02X %02X -> %*ph",
>  	     ret, SYNC_BYTE_OUT, id, addr << 1, snd_len, rcv_len,
> -	     buf[0], buf[1], buf[4], buf[5], buf[6]);
> -
> +	     7, state->data);
>  	return ret;
>  }
>  
> @@ -499,8 +497,7 @@ static u32 pctv452e_i2c_func(struct i2c_adapter
> *adapter) static int pctv452e_power_ctrl(struct dvb_usb_device *d,
> int i) {
>  	struct pctv452e_state *state = (struct pctv452e_state
> *)d->priv;
> -	u8 b0[] = { 0xaa, 0, PCTV_CMD_RESET, 1, 0 };
> -	u8 rx[PCTV_ANSWER_LEN];
> +	u8 *rx;
>  	int ret;
>  
>  	info("%s: %d\n", __func__, i);
> @@ -511,6 +508,10 @@ static int pctv452e_power_ctrl(struct
> dvb_usb_device *d, int i) if (state->initialized)
>  		return 0;
>  
> +	rx = kmalloc(PCTV_ANSWER_LEN, GFP_KERNEL);
> +	if (!rx)
> +		return -ENOMEM;
> +
>  	/* hmm where shoud this should go? */
>  	ret = usb_set_interface(d->udev, 0,
> ISOC_INTERFACE_ALTERNATIVE); if (ret != 0)
> @@ -518,57 +519,62 @@ static int pctv452e_power_ctrl(struct
> dvb_usb_device *d, int i) __func__, ret);
>  
>  	/* this is a one-time initialization, dont know where to put
> */
> -	b0[1] = state->c++;
> +	state->data[0] = 0xaa;
> +	state->data[1] = state->c++;
> +	state->data[2] = PCTV_CMD_RESET;
> +	state->data[3] = 1;
> +	state->data[4] = 0;
>  	/* reset board */
> -	ret = dvb_usb_generic_rw(d, b0, sizeof(b0), rx,
> PCTV_ANSWER_LEN, 0);
> +	ret = dvb_usb_generic_rw(d, state->data, 5, rx,
> PCTV_ANSWER_LEN, 0); if (ret)
> -		return ret;
> +		goto ret;
>  
> -	b0[1] = state->c++;
> -	b0[4] = 1;
> +	state->data[1] = state->c++;
> +	state->data[4] = 1;
>  	/* reset board (again?) */
> -	ret = dvb_usb_generic_rw(d, b0, sizeof(b0), rx,
> PCTV_ANSWER_LEN, 0);
> +	ret = dvb_usb_generic_rw(d, state->data, 5, rx,
> PCTV_ANSWER_LEN, 0); if (ret)
> -		return ret;
> +		goto ret;
>  
>  	state->initialized = 1;
>  
> -	return 0;
> +ret:
> +	kfree(rx);
> +	return ret;
>  }
>  
>  static int pctv452e_rc_query(struct dvb_usb_device *d)
>  {
>  	struct pctv452e_state *state = (struct pctv452e_state
> *)d->priv;
> -	u8 b[CMD_BUFFER_SIZE];
> -	u8 rx[PCTV_ANSWER_LEN];
>  	int ret, i;
>  	u8 id = state->c++;
>  
>  	/* prepare command header  */
> -	b[0] = SYNC_BYTE_OUT;
> -	b[1] = id;
> -	b[2] = PCTV_CMD_IR;
> -	b[3] = 0;
> +	state->data[0] = SYNC_BYTE_OUT;
> +	state->data[1] = id;
> +	state->data[2] = PCTV_CMD_IR;
> +	state->data[3] = 0;
>  
>  	/* send ir request */
> -	ret = dvb_usb_generic_rw(d, b, 4, rx, PCTV_ANSWER_LEN, 0);
> +	ret = dvb_usb_generic_rw(d, state->data, 4,
> +				 state->data, PCTV_ANSWER_LEN, 0);
>  	if (ret != 0)
>  		return ret;
>  
>  	if (debug > 3) {
> -		info("%s: read: %2d: %*ph: ", __func__, ret, 3, rx);
> -		for (i = 0; (i < rx[3]) && ((i+3) <
> PCTV_ANSWER_LEN); i++)
> -			info(" %02x", rx[i+3]);
> +		info("%s: read: %2d: %*ph: ", __func__, ret, 3,
> state->data);
> +		for (i = 0; (i < state->data[3]) && ((i + 3) <
> PCTV_ANSWER_LEN); i++)
> +			info(" %02x", state->data[i + 3]);
>  
>  		info("\n");
>  	}
>  
> -	if ((rx[3] == 9) &&  (rx[12] & 0x01)) {
> +	if ((state->data[3] == 9) &&  (state->data[12] & 0x01)) {
>  		/* got a "press" event */
> -		state->last_rc_key = RC_SCANCODE_RC5(rx[7], rx[6]);
> +		state->last_rc_key = RC_SCANCODE_RC5(state->data[7],
> state->data[6]); if (debug > 2)
>  			info("%s: cmd=0x%02x sys=0x%02x\n",
> -				__func__, rx[6], rx[7]);
> +				__func__, state->data[6],
> state->data[7]); 
>  		rc_keydown(d->rc_dev, RC_TYPE_RC5,
> state->last_rc_key, 0); } else if (state->last_rc_key) {

Reviewed-By: Patrick Boettcher <patrick.boettcher@posteo.de>