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authorJarod Wilson <jarod@redhat.com>2011-01-14 19:40:32 (GMT)
committerMauro Carvalho Chehab <mchehab@redhat.com>2011-01-17 23:23:30 (GMT)
commitb94b81e8d7b94dfcc80b5ff3659454e73e451e27 (patch)
tree2a4db720480af38d65310869fd1c96e97c55dd73
parent37634d7308c5c1bdde03ab703a3cac3f0fb12453 (diff)
[media] hdpvr: reduce latency of i2c read/write w/recycled buffer
The current hdpvr code kmalloc's a new buffer for every i2c read and write. Rather than do that, lets allocate a buffer in the driver's device struct and just use that every time. The size I've chosen for the buffer is the maximum size I could ascertain might be used by either ir-kbd-i2c or lirc_zilog, plus a bit of padding (lirc_zilog may use up to 100 bytes on tx, rounded that up to 128). Note that this might also remedy user reports of very sluggish behavior of IR receive with hdpvr hardware. v2: make sure (len <= (dev->i2c_buf)) [Jean Delvare] Reported-by: Jean Delvare <khali@linux-fr.org> Acked-by: Jean Delvare <khali@linux-fr.org> Signed-off-by: Jarod Wilson <jarod@redhat.com> Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
-rw-r--r--drivers/media/video/hdpvr/hdpvr-i2c.c30
-rw-r--r--drivers/media/video/hdpvr/hdpvr.h3
2 files changed, 16 insertions, 17 deletions
diff --git a/drivers/media/video/hdpvr/hdpvr-i2c.c b/drivers/media/video/hdpvr/hdpvr-i2c.c
index 45b88cf..89b71fa 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;

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