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SubjectRe: small patch: enable pwc usb camera driver
Greg KH wrote:
> On Tue, Jun 08, 2004 at 12:27:04AM +0200, Nemosoft Unv. wrote:
>> ...
>>Don't use this. It will BUG() your kernel hard, because of a double free().

I confirm, if you disconnect the device / unload the driver, it doesn't
take long and the kernel reports an exception. My fault, sorry.

> ... I'll wait for someone to send another patch fixing this one ...

I'm attaching a new patch:

- revert video device release code to original no-op,
using correct function signature.

With this patch applied to 2.6.7, I am able to connect/disconnect the
camera, load/unload the driver 20 times and everything still works fine.

No warnings during compilation (which was the original reason to mark
the driver broken, IIUC).

Thanks and Regards,
Kai
diff -ruw org-267/drivers/usb/media/pwc-if.c linux-2.6.7/drivers/usb/media/pwc-if.c
--- org-267/drivers/usb/media/pwc-if.c 2004-06-16 07:19:44.000000000 +0200
+++ linux-2.6.7/drivers/usb/media/pwc-if.c 2004-06-17 13:49:58.268336544 +0200
@@ -129,6 +129,7 @@

static int pwc_video_open(struct inode *inode, struct file *file);
static int pwc_video_close(struct inode *inode, struct file *file);
+static void pwc_video_release(struct video_device *);
static ssize_t pwc_video_read(struct file *file, char *buf,
size_t count, loff_t *ppos);
static unsigned int pwc_video_poll(struct file *file, poll_table *wait);
@@ -1120,6 +1121,12 @@
return 0;
}

+static void pwc_video_release(struct video_device *vfd)
+{
+ /* Do nothing to prevent a double free */
+ Trace(TRACE_OPEN, "pwc_video_release() called.\n");
+}
+
/*
* FIXME: what about two parallel reads ????
* ANSWER: Not supported. You can't open the device more than once,
@@ -1848,7 +1855,7 @@
}
}

- pdev->vdev.release = video_device_release;
+ pdev->vdev.release = pwc_video_release;
i = video_register_device(&pdev->vdev, VFL_TYPE_GRABBER, video_nr);
if (i < 0) {
Err("Failed to register as video device (%d).\n", i);
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