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SubjectRe: [PATCH 26/31] staging/comedi/das16: Make timer initialization unconditional
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On 01/09/17 10:29, Ian Abbott wrote:
> On 01/09/17 00:29, Kees Cook wrote:
>> With timer initialization made unconditional, there is no reason to
>> make del_timer_sync() calls conditionally, there by removing the test
>> of the .data field.
>>
>> Cc: Ian Abbott <abbotti@mev.co.uk>
>> Cc: H Hartley Sweeten <hsweeten@visionengravers.com>
>> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>> Cc: devel@driverdev.osuosl.org
>> Signed-off-by: Kees Cook <keescook@chromium.org>
>> ---
>> drivers/staging/comedi/drivers/das16.c | 9 +++------
>> 1 file changed, 3 insertions(+), 6 deletions(-)
>>
>> diff --git a/drivers/staging/comedi/drivers/das16.c
>> b/drivers/staging/comedi/drivers/das16.c
>> index 5d157951f63f..4514179b2007 100644
>> --- a/drivers/staging/comedi/drivers/das16.c
>> +++ b/drivers/staging/comedi/drivers/das16.c
>> @@ -941,10 +941,8 @@ static void das16_alloc_dma(struct comedi_device
>> *dev, unsigned int dma_chan)
>> /* DMA uses two buffers */
>> devpriv->dma = comedi_isadma_alloc(dev, 2, dma_chan, dma_chan,
>> DAS16_DMA_SIZE, COMEDI_ISADMA_READ);
>> - if (devpriv->dma) {
>> - setup_timer(&devpriv->timer, das16_timer_interrupt,
>> - (unsigned long)dev);
>> - }
>> + setup_timer(&devpriv->timer, das16_timer_interrupt,
>> + (unsigned long)dev);
>> }
>
> das16_alloc_dma() returns before the call to comedi_isadma_alloc() if
> the dma_chan parameter is not one of the values 1 or 3, so setup_timer()
> will not be called in that case.
>
>> static void das16_free_dma(struct comedi_device *dev)
>> @@ -952,8 +950,7 @@ static void das16_free_dma(struct comedi_device *dev)
>> struct das16_private_struct *devpriv = dev->private;
>> if (devpriv) {
>> - if (devpriv->timer.data)
>> - del_timer_sync(&devpriv->timer);
>> + del_timer_sync(&devpriv->timer);
>
> If setup_timer() has not been called (see remark above), this change
> will break.
>
>> comedi_isadma_free(devpriv->dma);
>> }
>> }
>>

If you want to avoid testing devpriv->timer.data for some reason, you
could make the calls to setup_timer() and del_timer_sync() depend on
devpriv->dma.

--
-=( Ian Abbott @ MEV Ltd. E-mail: <abbotti@mev.co.uk> )=-
-=( Web: http://www.mev.co.uk/ )=-

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