[v2] hdpvr: reduce latency of i2c read/write w/recycled buffer

Commit Message

Jarod Wilson Jan. 14, 2011, 9:08 p.m. UTC

None

Patch

diff --git a/drivers/media/video/hdpvr/hdpvr-i2c.c b/drivers/media/video/hdpvr/hdpvr-i2c.c
index c0696c3..2adfe90 100644
--- a/drivers/media/video/hdpvr/hdpvr-i2c.c
+++ b/drivers/media/video/hdpvr/hdpvr-i2c.c
@@ -57,23 +57,21 @@  static int hdpvr_i2c_read(struct hdpvr_device *dev, int bus,
 			  unsigned char addr, char *data, int len)
 {
 	int ret;
-	char *buf = kmalloc(len, GFP_KERNEL);
-	if (!buf)
-		return -ENOMEM;
+
+	if (len > sizeof(dev->i2c_buf))
+		return -EINVAL;
 
 	ret = usb_control_msg(dev->udev,
 			      usb_rcvctrlpipe(dev->udev, 0),
 			      REQTYPE_I2C_READ, CTRL_READ_REQUEST,
-			      (bus << 8) | addr, 0, buf, len, 1000);
+			      (bus << 8) | addr, 0, &dev->i2c_buf, len, 1000);
 
 	if (ret == len) {
-		memcpy(data, buf, len);
+		memcpy(data, &dev->i2c_buf, len);
 		ret = 0;
 	} else if (ret >= 0)
 		ret = -EIO;
 
-	kfree(buf);
-
 	return ret;
 }
 
@@ -81,31 +79,29 @@  static int hdpvr_i2c_write(struct hdpvr_device *dev, int bus,
 			   unsigned char addr, char *data, int len)
 {
 	int ret;
-	char *buf = kmalloc(len, GFP_KERNEL);
-	if (!buf)
-		return -ENOMEM;
 
-	memcpy(buf, data, len);
+	if (len > sizeof(dev->i2c_buf))
+		return -EINVAL;
+
+	memcpy(&dev->i2c_buf, data, len);
 	ret = usb_control_msg(dev->udev,
 			      usb_sndctrlpipe(dev->udev, 0),
 			      REQTYPE_I2C_WRITE, CTRL_WRITE_REQUEST,
-			      (bus << 8) | addr, 0, buf, len, 1000);
+			      (bus << 8) | addr, 0, &dev->i2c_buf, len, 1000);
 
 	if (ret < 0)
-		goto error;
+		return ret;
 
 	ret = usb_control_msg(dev->udev,
 			      usb_rcvctrlpipe(dev->udev, 0),
 			      REQTYPE_I2C_WRITE_STATT, CTRL_READ_REQUEST,
-			      0, 0, buf, 2, 1000);
+			      0, 0, &dev->i2c_buf, 2, 1000);
 
-	if ((ret == 2) && (buf[1] == (len - 1)))
+	if ((ret == 2) && (dev->i2c_buf[1] == (len - 1)))
 		ret = 0;
 	else if (ret >= 0)
 		ret = -EIO;
 
-error:
-	kfree(buf);
 	return ret;
 }
 
diff --git a/drivers/media/video/hdpvr/hdpvr.h b/drivers/media/video/hdpvr/hdpvr.h
index 29f7426..ee74e3b 100644
--- a/drivers/media/video/hdpvr/hdpvr.h
+++ b/drivers/media/video/hdpvr/hdpvr.h
@@ -25,6 +25,7 @@ 
 	KERNEL_VERSION(HDPVR_MAJOR_VERSION, HDPVR_MINOR_VERSION, HDPVR_RELEASE)
 
 #define HDPVR_MAX 8
+#define HDPVR_I2C_MAX_SIZE 128
 
 /* Define these values to match your devices */
 #define HD_PVR_VENDOR_ID	0x2040
@@ -109,6 +110,8 @@  struct hdpvr_device {
 	struct i2c_adapter	i2c_adapter;
 	/* I2C lock */
 	struct mutex		i2c_mutex;
+	/* I2C message buffer space */
+	char			i2c_buf[HDPVR_I2C_MAX_SIZE];
 
 	/* For passing data to ir-kbd-i2c */
 	struct IR_i2c_init_data	ir_i2c_init_data;