linux-kernel - Re: [PATCH 19/26] nova-t-usb2: don't do DMA on stack

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Date:   Mon, 10 Oct 2016 08:35:47 +0200
From:   Patrick Boettcher <patrick.boettcher@...teo.de>
To:     Mauro Carvalho Chehab <mchehab@...pensource.com>
Cc:     Linux Media Mailing List <linux-media@...r.kernel.org>,
        Mauro Carvalho Chehab <mchehab@...radead.org>,
        Andy Lutomirski <luto@...capital.net>,
        Johannes Stezenbach <js@...uxtv.org>,
        Jiri Kosina <jikos@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Andy Lutomirski <luto@...nel.org>,
        Michael Krufky <mkrufky@...uxtv.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Jörg Otte <jrg.otte@...il.com>
Subject: Re: [PATCH 19/26] nova-t-usb2: don't do DMA on stack

On Fri,  7 Oct 2016 14:24:29 -0300
Mauro Carvalho Chehab <mchehab@...pensource.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@...pensource.com>
> ---
>  drivers/media/usb/dvb-usb/nova-t-usb2.c | 18 +++++++++++++-----
>  1 file changed, 13 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/media/usb/dvb-usb/nova-t-usb2.c
> b/drivers/media/usb/dvb-usb/nova-t-usb2.c index
> fc7569e2728d..26d7188a1163 100644 ---
> a/drivers/media/usb/dvb-usb/nova-t-usb2.c +++
> b/drivers/media/usb/dvb-usb/nova-t-usb2.c @@ -74,22 +74,29 @@ static
> struct rc_map_table rc_map_haupp_table[] = { */
>  static int nova_t_rc_query(struct dvb_usb_device *d, u32 *event, int
> *state) {
> -	u8 key[5],cmd[2] = { DIBUSB_REQ_POLL_REMOTE, 0x35 },
> data,toggle,custom;
> +	u8 *buf, data, toggle, custom;
>  	u16 raw;
>  	int i;
>  	struct dibusb_device_state *st = d->priv;
>  
> -	dvb_usb_generic_rw(d,cmd,2,key,5,0);
> +	buf = kmalloc(5, GFP_KERNEL);
> +	if (!buf)
> +		return -ENOMEM;
> +
> +	buf[0] = DIBUSB_REQ_POLL_REMOTE;
> +	buf[1] = 0x35;
> +	dvb_usb_generic_rw(d, buf, 2, buf, 5, 0);
>  
>  	*state = REMOTE_NO_KEY_PRESSED;
> -	switch (key[0]) {
> +	switch (buf[0]) {
>  		case DIBUSB_RC_HAUPPAUGE_KEY_PRESSED:
> -			raw = ((key[1] << 8) | key[2]) >> 3;
> +			raw = ((buf[1] << 8) | buf[2]) >> 3;
>  			toggle = !!(raw & 0x800);
>  			data = raw & 0x3f;
>  			custom = (raw >> 6) & 0x1f;
>  
> -			deb_rc("raw key code 0x%02x, 0x%02x, 0x%02x
> to c: %02x d: %02x toggle:
> %d\n",key[1],key[2],key[3],custom,data,toggle);
> +			deb_rc("raw key code 0x%02x, 0x%02x, 0x%02x
> to c: %02x d: %02x toggle: %d\n",
> +			       buf[1], buf[2], buf[3], custom, data,
> toggle); 
>  			for (i = 0; i <
> ARRAY_SIZE(rc_map_haupp_table); i++) { if
> (rc5_data(&rc_map_haupp_table[i]) == data && @@ -117,6 +124,7 @@
> static int nova_t_rc_query(struct dvb_usb_device *d, u32 *event, int
> *state) break; }
>  
> +	kfree(buf);
>  	return 0;
>  }
>  

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