Re: [PATCH 3.16 - 3.18] staging: comedi: usbduxsigma: don't clobber ai_timer in command test

[Luis Henriques <luis.henriques@canonical.com>]

On Wed, Sep 16, 2015 at 02:17:14PM +0100, Ian Abbott wrote:
> commit 423b24c37dd5794a674c74b0ed56392003a69891 upstream
>

Thank you, Ian.  I'll queue these 2 backports for the 3.16 kernel.

Cheers,
--
Lu�s


> `devpriv->ai_timer` is used while an asynchronous command is running on
> the AI subdevice.  It also gets modified by the subdevice's `cmdtest`
> handler for checking new asynchronous commands
> (`usbduxsigma_ai_cmdtest()`), which is not correct as it's allowed to
> check new commands while an old command is still running.  Fix it by
> moving the code which sets up `devpriv->ai_timer` and
> `devpriv->ai_interval` into the subdevice's `cmd` handler,
> `usbduxsigma_ai_cmd()`.
> 
> ** This backported patch also moves the code that sets up
> `devpriv->ai_sample_count` from `usbduxsigma_ai_cmdtest()` to
> `usbduxsigma_ai_cmd()` for the same reason as above. (This was not
> needed in the upstream commit.) **
> 
> Note that the removed code in `usbduxsigma_ai_cmdtest()` checked that
> `devpriv->ai_timer` did not end up less than than 1, but that could not
> happen because `cmd->scan_begin_arg` had already been checked to be at
> least the minimum required value (at least when `cmd->scan_begin_src ==
> TRIG_TIMER`, which had also been checked to be the case).
> 
> Fixes: b986be8527c7 ("staging: comedi: usbduxsigma: tidy up analog input command support)
> Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
> ---
>  drivers/staging/comedi/drivers/usbduxsigma.c | 53 +++++++++++++---------------
>  1 file changed, 24 insertions(+), 29 deletions(-)
> 
> diff --git a/drivers/staging/comedi/drivers/usbduxsigma.c b/drivers/staging/comedi/drivers/usbduxsigma.c
> index ebd68e3..a6f87f0 100644
> --- a/drivers/staging/comedi/drivers/usbduxsigma.c
> +++ b/drivers/staging/comedi/drivers/usbduxsigma.c
> @@ -566,35 +566,6 @@ static int usbduxsigma_ai_cmdtest(struct comedi_device *dev,
>  	if (err)
>  		return 3;
>  
> -	/* Step 4: fix up any arguments */
> -
> -	if (high_speed) {
> -		/*
> -		 * every 2 channels get a time window of 125us. Thus, if we
> -		 * sample all 16 channels we need 1ms. If we sample only one
> -		 * channel we need only 125us
> -		 */
> -		devpriv->ai_interval = interval;
> -		devpriv->ai_timer = cmd->scan_begin_arg / (125000 * interval);
> -	} else {
> -		/* interval always 1ms */
> -		devpriv->ai_interval = 1;
> -		devpriv->ai_timer = cmd->scan_begin_arg / 1000000;
> -	}
> -	if (devpriv->ai_timer < 1)
> -		err |= -EINVAL;
> -
> -	if (cmd->stop_src == TRIG_COUNT) {
> -		/* data arrives as one packet */
> -		devpriv->ai_sample_count = cmd->stop_arg;
> -	} else {
> -		/* continuous acquisition */
> -		devpriv->ai_sample_count = 0;
> -	}
> -
> -	if (err)
> -		return 4;
> -
>  	return 0;
>  }
>  
> @@ -694,6 +665,30 @@ static int usbduxsigma_ai_cmd(struct comedi_device *dev,
>  
>  	/* set current channel of the running acquisition to zero */
>  	s->async->cur_chan = 0;
> +
> +	if (devpriv->high_speed) {
> +		/*
> +		 * every 2 channels get a time window of 125us. Thus, if we
> +		 * sample all 16 channels we need 1ms. If we sample only one
> +		 * channel we need only 125us
> +		 */
> +		unsigned int interval = usbduxsigma_chans_to_interval(len);
> +
> +		devpriv->ai_interval = interval;
> +		devpriv->ai_timer = cmd->scan_begin_arg / (125000 * interval);
> +	} else {
> +		/* interval always 1ms */
> +		devpriv->ai_interval = 1;
> +		devpriv->ai_timer = cmd->scan_begin_arg / 1000000;
> +	}
> +	if (cmd->stop_src == TRIG_COUNT) {
> +		/* data arrives as one packet */
> +		devpriv->ai_sample_count = cmd->stop_arg;
> +	} else {
> +		/* continuous acquisition */
> +		devpriv->ai_sample_count = 0;
> +	}
> +
>  	for (i = 0; i < len; i++) {
>  		unsigned int chan  = CR_CHAN(cmd->chanlist[i]);
>  
> -- 
> 2.5.1
> 
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