em28xx: avoid allocating/dealocating memory on every control urb

From: Mauro Carvalho Chehab <mchehab@redhat.com>

Before this patch, every register setup on em28xx were dynamically
allocating a temporary buffer for control URB's to be handled.

To avoid this ping-pong, use, instead a pre-allocated buffer.

Also, be sure that read control URB's also use the buffer, instead of
relying on a stack buffer.

Priority: high

Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

1 files changed, 5 insertions, 0 deletions

diff --git a/linux/drivers/media/video/em28xx/em28xx.h b/linux/drivers/media/video/em28xx/em28xx.h
index 97afac4b6..2e108be19 100644
--- a/linux/drivers/media/video/em28xx/em28xx.h
+++ b/linux/drivers/media/video/em28xx/em28xx.h
@@ -104,6 +104,9 @@
 #define EM28XX_MIN_BUF 4
 #define EM28XX_DEF_BUF 8
 
+/*Limits the max URB message size */
+#define URB_MAX_CTRL_SIZE 80
+
 /* Params for validated field */
 #define EM28XX_BOARD_NOT_VALIDATED 1
 #define EM28XX_BOARD_VALIDATED	   0
@@ -468,6 +471,8 @@ struct em28xx {
 	unsigned int *alt_max_pkt_size;	/* array of wMaxPacketSize */
 	struct urb *urb[EM28XX_NUM_BUFS];	/* urb for isoc transfers */
 	char *transfer_buffer[EM28XX_NUM_BUFS];	/* transfer buffers for isoc transfer */
+	char urb_buf[URB_MAX_CTRL_SIZE];	/* urb control msg buffer */
+
 	/* helper funcs that call usb_control_msg */
 	int (*em28xx_write_regs) (struct em28xx *dev, u16 reg,
 					char *buf, int len);