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Date:	Fri, 18 May 2012 17:32:04 -0700
From:	Greg KH <>
To:	H Hartley Sweeten <>
Cc:	Linux Kernel <>,,,
Subject: Re: [PATCH] staging: comedi: cleanup all the comedi_driver 'detach'

On Thu, May 17, 2012 at 05:11:14PM -0700, H Hartley Sweeten wrote:
> 1. Change the return type from int to void
> All the detach functions, except for the comedi usb drivers, simply
> return success (0). Plus, the return code is never checked in the
> comedi core.
> The comedi usb drivers do return error codes but the conditions can
> never happen.
> The first check is:
> 	if (!dev)
> 		return -EFAULT;
> This checks that the passed comedi_device pointer is valid. The detach
> function itself is called using this pointer so it MUST always be valid
> or there is a bug in the core:
> 	if (dev->driver)
> 		dev->driver->detach(dev);
> And the second check:
> 	usb = dev->private;
> 	if (!usb)
> 		return -EFAULT;
> The dev->private pointer is setup in the attach function to point to the
> probed usb device. This value could be NULL if the attach fails. But,
> since the comedi core is going to unload the driver anyway and does not
> check for errors there is no gain by returning one.
> After removing these checks from the comedi usb drivers the detach
> functions required a bit of cleanup.
> 2. Remove all the printk noise in the detach functions
> All of the printk output is really just noise. The user did a rmmod to
> unload the driver, we really don't need to tell them about it.
> Also, some of the messages are output using:
> 	dev_dbg(dev->hw_dev, ...
> or
> 	dev_info(dev->hw_dev, ...
> Unfortunately the hw_dev value is only used by drivers that are doing
> DMA. For most drivers this variable is going to be NULL so the output
> is not going to work as expected.

Sorry about that, I probably caused a lot of that.  As no one ever
complained, odds are no one is using those drivers :)

> 3. Refactor a couple static 'free_resource' functions into the detach
>    functions.
> The 'free_resource' function is only being called by the detach and it
> makes more sense to just absorb the code.
> 4. Remove a couple unnecessary braces for single statements.
> 5. Remove unnecessary comments.
> Most of the comedi drivers appear to be based on the comedi skel driver
> and have the comments from that driver included. These comments make
> sense in the skel driver for reference but they don't need to be in any
> of the actual drivers.
> 6. Remove all the extra whitespace.
> It's not needed to make the functions any more readable.
> 7. Remove the now unused 'attached_successfully' variable in the
>    cb_pcimdda driver.
> This variable was only used to conditionally output some driver noise
> during the detach. Since all the printk's have been removed this
> variable is no longer necessary.
> Signed-off-by: H Hartley Sweeten <>
> Cc: Ian Abbott <>
> Cc: Mori Hess <>
> ---
> This is a pretty large patch but it's mostly line removal. I can break
> it up if necessary.

Not a problem this time, I've taken it as-is, as I need to close the
merge window in a few minutes...


greg k-h
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