[PATCH 1/2] staging/comedi/drivers: release allocated I/O region if alloc_private fails

[PATCH 1/2] staging/comedi/drivers: release allocated I/O region if alloc_private fails

[Devendra Naga]

if alloc_private fail, we wont' release the I/O region,
which was request_region 'ed.

release the allocated I/O region if alloc_private fails.

Signed-off-by: Devendra Naga <devendra.aaru@gmail.com>
---
 drivers/staging/comedi/drivers/fl512.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/staging/comedi/drivers/fl512.c b/drivers/staging/comedi/drivers/fl512.c
index d1da809..52e6d14 100644
--- a/drivers/staging/comedi/drivers/fl512.c
+++ b/drivers/staging/comedi/drivers/fl512.c
@@ -125,8 +125,10 @@ static int fl512_attach(struct comedi_device *dev, struct comedi_devconfig *it)
 	}
 	dev->iobase = iobase;
 	dev->board_name = "fl512";
-	if (alloc_private(dev, sizeof(struct fl512_private)) < 0)
+	if (alloc_private(dev, sizeof(struct fl512_private)) < 0) {
+		release_region(iobase, FL512_SIZE);
 		return -ENOMEM;
+	}
 
 #if DEBUG
 	printk(KERN_DEBUG "malloc ok\n");
-- 
1.7.9.5

Re: [PATCH 1/2] staging/comedi/drivers: release allocated I/O region if alloc_private fails

[Ian Abbott]

On 2012-07-01 14:36, Devendra Naga wrote:
> if alloc_private fail, we wont' release the I/O region,
> which was request_region 'ed.
>
> release the allocated I/O region if alloc_private fails.
>
> Signed-off-by: Devendra Naga <devendra.aaru@gmail.com>
> ---
>   drivers/staging/comedi/drivers/fl512.c |    4 +++-
>   1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/staging/comedi/drivers/fl512.c b/drivers/staging/comedi/drivers/fl512.c
> index d1da809..52e6d14 100644
> --- a/drivers/staging/comedi/drivers/fl512.c
> +++ b/drivers/staging/comedi/drivers/fl512.c
> @@ -125,8 +125,10 @@ static int fl512_attach(struct comedi_device *dev, struct comedi_devconfig *it)
>   	}
>   	dev->iobase = iobase;
>   	dev->board_name = "fl512";
> -	if (alloc_private(dev, sizeof(struct fl512_private)) < 0)
> +	if (alloc_private(dev, sizeof(struct fl512_private)) < 0) {
> +		release_region(iobase, FL512_SIZE);
>   		return -ENOMEM;
> +	}
>
>   #if DEBUG
>   	printk(KERN_DEBUG "malloc ok\n");

No.  The I/O region will be deallocated in fl512_detach() because 
dev->iobase has been set non-zero.  fl512_detach() will be called by the 
comedi core if fl512_attach() returns an error.  This is an unusual 
aspect of the comedi drivers.

-- 
-=( Ian Abbott @ MEV Ltd.    E-mail: <abbotti@mev.co.uk>        )=-
-=( Tel: +44 (0)161 477 1898   FAX: +44 (0)161 718 3587         )=-

Re: [PATCH 1/2] staging/comedi/drivers: release allocated I/O region if alloc_private fails

[devendra.aaru]

On Mon, Jul 2, 2012 at 2:10 PM, Ian Abbott <abbotti@mev.co.uk> wrote:
> On 2012-07-01 14:36, Devendra Naga wrote:
>>
>> if alloc_private fail, we wont' release the I/O region,
>> which was request_region 'ed.
>>
>> release the allocated I/O region if alloc_private fails.
>>
>> Signed-off-by: Devendra Naga <devendra.aaru@gmail.com>
>> ---
>
>
> No.  The I/O region will be deallocated in fl512_detach() because
> dev->iobase has been set non-zero.  fl512_detach() will be called by the
> comedi core if fl512_attach() returns an error.  This is an unusual aspect
> of the comedi drivers.
>
Oh, i didn't see the comedi core, i went and saw that its not freed
up, so actaully driver unload wont' be called if driver attach , probe
fail. so i started sending this patch.

Sorry.
> --
> -=( Ian Abbott @ MEV Ltd.    E-mail: <abbotti@mev.co.uk>        )=-
> -=( Tel: +44 (0)161 477 1898   FAX: +44 (0)161 718 3587         )=-

Devendra.

RE: [PATCH 1/2] staging/comedi/drivers: release allocated I/O region if alloc_private fails

[H Hartley Sweeten]

On Monday, July 02, 2012 1:41 AM, Ian Abbott wrote:
> No.  The I/O region will be deallocated in fl512_detach() because 
> dev->iobase has been set non-zero.  fl512_detach() will be called by the 
> comedi core if fl512_attach() returns an error.  This is an unusual 
> aspect of the comedi drivers.

I have been wondering if that aspect should be "fixed".

It's more typical for kernel drivers to clean up after themselves if
the probe/attach/init/etc. fails. And the release/detach/exit/etc.
is only called if the driver has successfully loaded.

With the comedi drivers, the "detach" is always called if the "attach"
failed. And, of course the "detach" is called when the device is removed.

Because of this the "detach" routines need to do all the checks to
see what needs to be cleaned up. Not a big deal but it does create
some confusion as this patch shows.

Ian, what's your opinion on this? Do you think we should refactor all
the driver "attach" routines so they clean up on failure and fix the
core so the "detach" is only called after a successful "attach"?

This would be a pretty big patch since it affects every driver as well
as the core. 

We could break it up by introducing a temporary flag in the comedi_driver
struct that indicates if the driver has been "fixed". The core could then
work as-is for non-updated drivers. Once all the drivers have been updated
we then fix the core and remove the flag from all the drivers.

Regards,
Hartley

Re: [PATCH 1/2] staging/comedi/drivers: release allocated I/O region if alloc_private fails

[Ian Abbott]

On 2012-07-02 16:57, H Hartley Sweeten wrote:
> On Monday, July 02, 2012 1:41 AM, Ian Abbott wrote:
>> No.  The I/O region will be deallocated in fl512_detach() because
>> dev->iobase has been set non-zero.  fl512_detach() will be called by the
>> comedi core if fl512_attach() returns an error.  This is an unusual
>> aspect of the comedi drivers.
>
> I have been wondering if that aspect should be "fixed".
>
> It's more typical for kernel drivers to clean up after themselves if
> the probe/attach/init/etc. fails. And the release/detach/exit/etc.
> is only called if the driver has successfully loaded.
>
> With the comedi drivers, the "detach" is always called if the "attach"
> failed. And, of course the "detach" is called when the device is removed.
>
> Because of this the "detach" routines need to do all the checks to
> see what needs to be cleaned up. Not a big deal but it does create
> some confusion as this patch shows.

At the very least, this behaviour should be documented with a comment at 
the appropriate place in comedidev.h.

I think Comedi's current clean-up model is based on the open/close model 
of TTY driver operations, where the 'close' tty_operation is called when 
the 'open' tty_operation fails (although typically these operations 
don't do much allocation or deallocation).

> Ian, what's your opinion on this? Do you think we should refactor all
> the driver "attach" routines so they clean up on failure and fix the
> core so the "detach" is only called after a successful "attach"?

It would be nicer, although the existing mechanism does have the slight 
advantage of using less code.

If this mechanism is adopted, drivers using the new mechanism should 
also be responsible for freeing their subdevices (which will need a new 
function comedi_free_subdevices()) and their comedi_device private data. 
  (They're already responsible for freeing comedi_subdevice private data 
in their 'detach' routines.)

> This would be a pretty big patch since it affects every driver as well
> as the core.
>
> We could break it up by introducing a temporary flag in the comedi_driver
> struct that indicates if the driver has been "fixed". The core could then
> work as-is for non-updated drivers. Once all the drivers have been updated
> we then fix the core and remove the flag from all the drivers.

That sounds like a reasonable plan.

-- 
-=( Ian Abbott @ MEV Ltd.    E-mail: <abbotti@mev.co.uk>        )=-
-=( Tel: +44 (0)161 477 1898   FAX: +44 (0)161 718 3587         )=-