V4L/DVB (9646): em28xx: avoid allocating/dealocating memory on every control urb

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.

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

diff --git a/drivers/media/video/em28xx/em28xx-core.c b/drivers/media/video/em28xx/em28xx-core.c
index 038da614a7349dcdfaf87833be9b64cf496fc43c..9551b8ab8c446e8a0d10ce4d813697683098f8db 100644 (file)
--- a/drivers/media/video/em28xx/em28xx-core.c
+++ b/drivers/media/video/em28xx/em28xx-core.c
@@ -69,19 +69,29 @@ int em28xx_read_reg_req_len(struct em28xx *dev, u8 req, u16 reg,
        int ret, byte;
 
        if (dev->state & DEV_DISCONNECTED)
-               return(-ENODEV);
+               return -ENODEV;
+
+       if (len > URB_MAX_CTRL_SIZE)
+               return -EINVAL;
 
        em28xx_regdbg("req=%02x, reg=%02x ", req, reg);
 
        ret = usb_control_msg(dev->udev, usb_rcvctrlpipe(dev->udev, 0), req,
                              USB_DIR_IN | USB_TYPE_VENDOR | USB_RECIP_DEVICE,
-                             0x0000, reg, buf, len, HZ);
+                             0x0000, reg, dev->urb_buf, len, HZ);
+       if (ret < 0) {
+               if (reg_debug)
+                       printk(" failed!\n");
+               return ret;
+       }
+
+       if (len)
+               memcpy(buf, dev->urb_buf, len);
 
        if (reg_debug) {
-               printk(ret < 0 ? " failed!\n" : "%02x values: ", ret);
+               printk("%02x values: ", ret);
                for (byte = 0; byte < len; byte++)
                        printk(" %02x", (unsigned char)buf[byte]);
-
                printk("\n");
        }
 
@@ -104,14 +114,16 @@ int em28xx_read_reg_req(struct em28xx *dev, u8 req, u16 reg)
 
        ret = usb_control_msg(dev->udev, usb_rcvctrlpipe(dev->udev, 0), req,
                              USB_DIR_IN | USB_TYPE_VENDOR | USB_RECIP_DEVICE,
-                             0x0000, reg, &val, 1, HZ);
+                             0x0000, reg, dev->urb_buf, 1, HZ);
+       if (ret < 0) {
+               printk(" failed!\n");
+               return ret;
+       }
 
-       if (reg_debug)
-               printk(ret < 0 ? " failed!\n" :
-                                "%02x\n", (unsigned char) val);
+       val = dev->urb_buf[0];
 
-       if (ret < 0)
-               return ret;
+       if (reg_debug)
+               printk("%02x\n", (unsigned char) val);
 
        return val;
 }
@@ -130,19 +142,13 @@ int em28xx_write_regs_req(struct em28xx *dev, u8 req, u16 reg, char *buf,
 {
        int ret;
 
-       /*usb_control_msg seems to expect a kmalloced buffer */
-       unsigned char *bufs;
-
        if (dev->state & DEV_DISCONNECTED)
                return -ENODEV;
 
-       if (len < 1)
+       if ((len < 1) || (len > URB_MAX_CTRL_SIZE))
                return -EINVAL;
 
-       bufs = kmalloc(len, GFP_KERNEL);
-
        em28xx_regdbg("req=%02x reg=%02x:", req, reg);
-
        if (reg_debug) {
                int i;
                for (i = 0; i < len; ++i)
@@ -150,16 +156,14 @@ int em28xx_write_regs_req(struct em28xx *dev, u8 req, u16 reg, char *buf,
                printk("\n");
        }
 
-       if (!bufs)
-               return -ENOMEM;
-       memcpy(bufs, buf, len);
+       memcpy(dev->urb_buf, buf, len);
        ret = usb_control_msg(dev->udev, usb_sndctrlpipe(dev->udev, 0), req,
                              USB_DIR_OUT | USB_TYPE_VENDOR | USB_RECIP_DEVICE,
-                             0x0000, reg, bufs, len, HZ);
+                             0x0000, reg, dev->urb_buf, len, HZ);
+
        if (dev->wait_after_write)
                msleep(dev->wait_after_write);
 
-       kfree(bufs);
        return ret;
 }
 

diff --git a/drivers/media/video/em28xx/em28xx.h b/drivers/media/video/em28xx/em28xx.h
index 82781178e0a3e23c7514a09bf6600c02d658ae36..1adf3d9d9bffaebcb8565d42f7bc6082ffd58b80 100644 (file)
--- a/drivers/media/video/em28xx/em28xx.h
+++ b/drivers/media/video/em28xx/em28xx.h
@@ -102,6 +102,9 @@
 #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
@@ -451,6 +454,8 @@ 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);