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SubjectRe: [PATCH v4] Staging: comedi: convert while loop to timeout in ni_mio_common.c
On 2014-01-15 03:58, Greg KH wrote:
> On Tue, Jan 14, 2014 at 06:23:05PM -0600, Chase Southwood wrote:
>> This patch for ni_mio_common.c changes out a while loop for a timeout,
>> which is preferred.
>>
>> Signed-off-by: Chase Southwood <chase.southwood@yahoo.com>
>> ---
>>
>> OK, here's another go at it. Hopefully everything looks more correct
>> this time. Greg, I've followed the pattern you gave me, and I really
>> appreciate all of the tips! As always, just let me know if there are
>> still things that need adjusting (especially length of timeout, udelay,
>> etc.).
>>
>> Thanks,
>> Chase Southwood
>>
>> 2: Changed from simple clean-up to swapping a timeout in for a while loop.
>>
>> 3: Removed extra counter variable, and added error checking.
>>
>> 4: No longer using counter variable, using jiffies instead.
>>
>> drivers/staging/comedi/drivers/ni_mio_common.c | 11 ++++++++++-
>> 1 file changed, 10 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/staging/comedi/drivers/ni_mio_common.c b/drivers/staging/comedi/drivers/ni_mio_common.c
>> index 457b884..882b249 100644
>> --- a/drivers/staging/comedi/drivers/ni_mio_common.c
>> +++ b/drivers/staging/comedi/drivers/ni_mio_common.c
>> @@ -687,12 +687,21 @@ static void ni_clear_ai_fifo(struct comedi_device *dev)
>> {
>> const struct ni_board_struct *board = comedi_board(dev);
>> struct ni_private *devpriv = dev->private;
>> + unsigned long timeout;
>>
>> if (board->reg_type == ni_reg_6143) {
>> /* Flush the 6143 data FIFO */
>> ni_writel(0x10, AIFIFO_Control_6143); /* Flush fifo */
>> ni_writel(0x00, AIFIFO_Control_6143); /* Flush fifo */
>> - while (ni_readl(AIFIFO_Status_6143) & 0x10) ; /* Wait for complete */
>> + /* Wait for complete */
>> + timeout = jiffies + msec_to_jiffies(100);
>> + while (ni_readl(AIFIFO_Status_6143) & 0x10) {
>> + if (time_after(jiffies, timeout)) {
>> + comedi_error(dev, "FIFO flush timeout.");
>> + break;
>> + }
>> + udelay(1);
>
> Sleep for at least 10, as I think that's the smallest time delay you can
> sleep for anyway (meaning it will be that long no matter what number you
> put there less than 10, depending on the hardware used of course.)

udelay() doesn't sleep (though it may get pre-empted) and I think you
can use any value you like within reason (up to a few 1000 microseconds).

>
> Other than that, looks much better.
>
> thanks,
>
> greg k-h
>


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


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