Re: [PATCH 06/26] cxusb: don't do DMA on stack

[Patrick Boettcher]

On Fri,  7 Oct 2016 14:24:16 -0300
Mauro Carvalho Chehab  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 
> ---
>  drivers/media/usb/dvb-usb/cxusb.c | 20 +++-
>  drivers/media/usb/dvb-usb/cxusb.h |  5 +
>  2 files changed, 12 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/media/usb/dvb-usb/cxusb.c
> b/drivers/media/usb/dvb-usb/cxusb.c index 907ac01ae297..f3615349de52
> 100644 --- a/drivers/media/usb/dvb-usb/cxusb.c
> +++ b/drivers/media/usb/dvb-usb/cxusb.c
> @@ -45,9 +45,6 @@
>  #include "si2168.h"
>  #include "si2157.h"
>  
> -/* Max transfer size done by I2C transfer functions */
> -#define MAX_XFER_SIZE  80
> -
>  /* debug */
>  static int dvb_usb_cxusb_debug;
>  module_param_named(debug, dvb_usb_cxusb_debug, int, 0644);
> @@ -61,23 +58,20 @@ DVB_DEFINE_MOD_OPT_ADAPTER_NR(adapter_nr);
>  static int cxusb_ctrl_msg(struct dvb_usb_device *d,
> u8 cmd, u8 *wbuf, int wlen, u8 *rbuf, int
> rlen) {
> + struct cxusb_state *st = d->priv;
>   int wo = (rbuf == NULL || rlen == 0); /* write-only */
> - u8 sndbuf[MAX_XFER_SIZE];
>  
> - if (1 + wlen > sizeof(sndbuf)) {
> - warn("i2c wr: len=%d is too big!\n",
> -  wlen);
> + if (1 + wlen > MAX_XFER_SIZE) {
> + warn("i2c wr: len=%d is too big!\n", wlen);
>   return -EOPNOTSUPP;
>   }
>  
> - memset(sndbuf, 0, 1+wlen);
> -
> - sndbuf[0] = cmd;
> - memcpy([1], wbuf, wlen);
> + st->data[0] = cmd;
> + memcpy(>data[1], wbuf, wlen);
>   if (wo)
> - return dvb_usb_generic_write(d, sndbuf, 1+wlen);
> + return dvb_usb_generic_write(d, st->data, 1 + wlen);
>   else
> - return dvb_usb_generic_rw(d, sndbuf, 1+wlen, rbuf,
> rlen, 0);
> + return dvb_usb_generic_rw(d, st->data, 1 + wlen,
> rbuf, rlen, 0); }
>  
>  /* GPIO */
> diff --git a/drivers/media/usb/dvb-usb/cxusb.h
> b/drivers/media/usb/dvb-usb/cxusb.h index 527ff7905e15..18acda19527a
> 100644 --- a/drivers/media/usb/dvb-usb/cxusb.h
> +++ b/drivers/media/usb/dvb-usb/cxusb.h
> @@ -28,10 +28,15 @@
>  #define CMD_ANALOG0x50
>  #define CMD_DIGITAL   0x51
>  
> +/* Max transfer size done by I2C transfer functions */
> +#define MAX_XFER_SIZE  80
> +
>  struct cxusb_state {
>   u8 gpio_write_state[3];
>   struct i2c_client *i2c_client_demod;
>   struct i2c_client *i2c_client_tuner;
> +
> + unsigned char data[MAX_XFER_SIZE];
>  };
>  
>  #endif

Reviewed-By: Patrick Boettcher 
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[PATCH 06/26] cxusb: don't do DMA on stack

[Mauro Carvalho Chehab]

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 
---
 drivers/media/usb/dvb-usb/cxusb.c | 20 +++-
 drivers/media/usb/dvb-usb/cxusb.h |  5 +
 2 files changed, 12 insertions(+), 13 deletions(-)

diff --git a/drivers/media/usb/dvb-usb/cxusb.c 
b/drivers/media/usb/dvb-usb/cxusb.c
index 907ac01ae297..f3615349de52 100644
--- a/drivers/media/usb/dvb-usb/cxusb.c
+++ b/drivers/media/usb/dvb-usb/cxusb.c
@@ -45,9 +45,6 @@
 #include "si2168.h"
 #include "si2157.h"
 
-/* Max transfer size done by I2C transfer functions */
-#define MAX_XFER_SIZE  80
-
 /* debug */
 static int dvb_usb_cxusb_debug;
 module_param_named(debug, dvb_usb_cxusb_debug, int, 0644);
@@ -61,23 +58,20 @@ DVB_DEFINE_MOD_OPT_ADAPTER_NR(adapter_nr);
 static int cxusb_ctrl_msg(struct dvb_usb_device *d,
  u8 cmd, u8 *wbuf, int wlen, u8 *rbuf, int rlen)
 {
+   struct cxusb_state *st = d->priv;
int wo = (rbuf == NULL || rlen == 0); /* write-only */
-   u8 sndbuf[MAX_XFER_SIZE];
 
-   if (1 + wlen > sizeof(sndbuf)) {
-   warn("i2c wr: len=%d is too big!\n",
-wlen);
+   if (1 + wlen > MAX_XFER_SIZE) {
+   warn("i2c wr: len=%d is too big!\n", wlen);
return -EOPNOTSUPP;
}
 
-   memset(sndbuf, 0, 1+wlen);
-
-   sndbuf[0] = cmd;
-   memcpy([1], wbuf, wlen);
+   st->data[0] = cmd;
+   memcpy(>data[1], wbuf, wlen);
if (wo)
-   return dvb_usb_generic_write(d, sndbuf, 1+wlen);
+   return dvb_usb_generic_write(d, st->data, 1 + wlen);
else
-   return dvb_usb_generic_rw(d, sndbuf, 1+wlen, rbuf, rlen, 0);
+   return dvb_usb_generic_rw(d, st->data, 1 + wlen, rbuf, rlen, 0);
 }
 
 /* GPIO */
diff --git a/drivers/media/usb/dvb-usb/cxusb.h 
b/drivers/media/usb/dvb-usb/cxusb.h
index 527ff7905e15..18acda19527a 100644
--- a/drivers/media/usb/dvb-usb/cxusb.h
+++ b/drivers/media/usb/dvb-usb/cxusb.h
@@ -28,10 +28,15 @@
 #define CMD_ANALOG0x50
 #define CMD_DIGITAL   0x51
 
+/* Max transfer size done by I2C transfer functions */
+#define MAX_XFER_SIZE  80
+
 struct cxusb_state {
u8 gpio_write_state[3];
struct i2c_client *i2c_client_demod;
struct i2c_client *i2c_client_tuner;
+
+   unsigned char data[MAX_XFER_SIZE];
 };
 
 #endif
-- 
2.7.4


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