linux-kernel - Re: [PATCH 5/6] staging: comedi: usbduxsigma: remove unused "convert" timing for AO

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Message-ID: <55B26EDB.9060707@berndporr.me.uk>
Date:	Fri, 24 Jul 2015 17:59:07 +0100
From:	Bernd Porr <mail@...ndporr.me.uk>
To:	Ian Abbott <abbotti@....co.uk>
CC:	driverdev-devel@...uxdriverproject.org,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	H Hartley Sweeten <hsweeten@...ionengravers.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/6] staging: comedi: usbduxsigma: remove unused "convert"
 timing for AO

Reviewed-by: Bernd Porr <mail@...ndporr.me.uk>

Ian Abbott wrote:
> The `cmdtest` and `cmd` handlers for the AO subdevice
> (`usbduxsigma_ao_cmdtest()` and `usbduxsigma_ao_cmd()`) support "scan"
> timing of commands with all channels updated every "scan" period.  There
> is some disabled code to use "convert" timing in high speed mode.  That
> would allow channels to be updated sequentially every "convert" period.
> Since that code is incomplete and currently disabled, remove it to
> simplify the existing code.
> 
> Signed-off-by: Ian Abbott <abbotti@....co.uk>
> ---
>  drivers/staging/comedi/drivers/usbduxsigma.c | 58 ++++++++--------------------
>  1 file changed, 17 insertions(+), 41 deletions(-)
> 
> diff --git a/drivers/staging/comedi/drivers/usbduxsigma.c b/drivers/staging/comedi/drivers/usbduxsigma.c
> index 4655048..d97253e 100644
> --- a/drivers/staging/comedi/drivers/usbduxsigma.c
> +++ b/drivers/staging/comedi/drivers/usbduxsigma.c
> @@ -838,28 +838,20 @@ static int usbduxsigma_ao_cmdtest(struct comedi_device *dev,
>  {
>  	struct usbduxsigma_private *devpriv = dev->private;
>  	int err = 0;
> -	int high_speed;
> -	unsigned int flags;
> -
> -	/* high speed conversions are not used yet */
> -	high_speed = 0;		/* (devpriv->high_speed) */
>  
>  	/* Step 1 : check if triggers are trivially valid */
>  
>  	err |= comedi_check_trigger_src(&cmd->start_src, TRIG_NOW | TRIG_INT);
>  
> -	if (high_speed) {
> -		/*
> -		 * start immediately a new scan
> -		 * the sampling rate is set by the coversion rate
> -		 */
> -		flags = TRIG_FOLLOW;
> -	} else {
> -		/* start a new scan (output at once) with a timer */
> -		flags = TRIG_TIMER;
> -	}
> -	err |= comedi_check_trigger_src(&cmd->scan_begin_src, flags);
> -
> +	/*
> +	 * For now, always use "scan" timing with all channels updated at once
> +	 * (cmd->scan_begin_src == TRIG_TIMER, cmd->convert_src == TRIG_NOW).
> +	 *
> +	 * In a future version, "convert" timing with channels updated
> +	 * indivually may be supported in high speed mode
> +	 * (cmd->scan_begin_src == TRIG_FOLLOW, cmd->convert_src == TRIG_TIMER).
> +	 */
> +	err |= comedi_check_trigger_src(&cmd->scan_begin_src, TRIG_TIMER);
>  	err |= comedi_check_trigger_src(&cmd->convert_src, TRIG_NOW);
>  	err |= comedi_check_trigger_src(&cmd->scan_end_src, TRIG_COUNT);
>  	err |= comedi_check_trigger_src(&cmd->stop_src, TRIG_COUNT | TRIG_NONE);
> @@ -883,17 +875,7 @@ static int usbduxsigma_ao_cmdtest(struct comedi_device *dev,
>  
>  	err |= comedi_check_trigger_arg_is(&cmd->start_arg, 0);
>  
> -	if (cmd->scan_begin_src == TRIG_FOLLOW)	/* internal trigger */
> -		err |= comedi_check_trigger_arg_is(&cmd->scan_begin_arg, 0);
> -
> -	if (cmd->scan_begin_src == TRIG_TIMER) {
> -		err |= comedi_check_trigger_arg_min(&cmd->scan_begin_arg,
> -						    1000000);
> -	}
> -
> -	/* not used now, is for later use */
> -	if (cmd->convert_src == TRIG_TIMER)
> -		err |= comedi_check_trigger_arg_min(&cmd->convert_arg, 125000);
> +	err |= comedi_check_trigger_arg_min(&cmd->scan_begin_arg, 1000000);
>  
>  	err |= comedi_check_trigger_arg_is(&cmd->scan_end_arg,
>  					   cmd->chanlist_len);
> @@ -918,19 +900,13 @@ static int usbduxsigma_ao_cmd(struct comedi_device *dev,
>  
>  	down(&devpriv->sem);
>  
> -	if (cmd->convert_src == TRIG_TIMER) {
> -		/*
> -		 * timing of the conversion itself: every 125 us
> -		 * at high speed (not used yet)
> -		 */
> -		devpriv->ao_timer = cmd->convert_arg / 125000;
> -	} else {
> -		/*
> -		 * timing of the scan: every 1ms
> -		 * we get all channels at once
> -		 */
> -		devpriv->ao_timer = cmd->scan_begin_arg / 1000000;
> -	}
> +	/*
> +	 * For now, only "scan" timing is supported.  A future version may
> +	 * support "convert" timing in high speed mode.
> +	 *
> +	 * Timing of the scan: every 1ms all channels updated at once.
> +	 */
> +	devpriv->ao_timer = cmd->scan_begin_arg / 1000000;
>  
>  	devpriv->ao_counter = devpriv->ao_timer;
>  

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