linux-kernel - Re: [PATCH] media: davinci: vpif: add check for NULL handler

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Date:	Fri, 17 Aug 2012 11:15:46 +0200
From:	Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:	Prabhakar Lad <prabhakar.lad@...com>
Cc:	Sekhar Nori <nsekhar@...com>,
	davinci-linux-open-source@...ux.davincidsp.com,
	linux-kernel@...r.kernel.org,
	Mauro Carvalho Chehab <mchehab@...radead.org>,
	Hans Verkuil <hans.verkuil@...co.com>,
	LMML <linux-media@...r.kernel.org>,
	Manjunath Hadli <manjunath.hadli@...com>
Subject: Re: [PATCH] media: davinci: vpif: add check for NULL handler

Hi Prabhakar,

On Friday 17 August 2012 14:02:19 Prabhakar Lad wrote:
> On Friday 17 August 2012 11:07 AM, Sekhar Nori wrote:
> > On 8/17/2012 10:51 AM, Prabhakar Lad wrote:
> >> On Thursday 16 August 2012 08:43 PM, Laurent Pinchart wrote:
> >>> On Thursday 16 August 2012 19:32:00 Prabhakar Lad wrote:
> >>>> From: Lad, Prabhakar <prabhakar.lad@...com>
> >>>> 
> >>>> Signed-off-by: Lad, Prabhakar <prabhakar.lad@...com>
> >>>> Signed-off-by: Manjunath Hadli <manjunath.hadli@...com>
> >>>> Cc: Hans Verkuil <hans.verkuil@...co.com>
> >>>> ---
> >>>> 
> >>>>  drivers/media/video/davinci/vpif_capture.c |   12 +++++++-----
> >>>>  drivers/media/video/davinci/vpif_display.c |   14 ++++++++------
> >>>>  2 files changed, 15 insertions(+), 11 deletions(-)
> >>>> 
> >>>> diff --git a/drivers/media/video/davinci/vpif_capture.c
> >>>> b/drivers/media/video/davinci/vpif_capture.c index 266025e..a87b7a5
> >>>> 100644
> >>>> --- a/drivers/media/video/davinci/vpif_capture.c
> >>>> +++ b/drivers/media/video/davinci/vpif_capture.c
> >>>> @@ -311,12 +311,14 @@ static int vpif_start_streaming(struct vb2_queue
> >>>> *vq,
> >>>> unsigned int count) }
> >>>> 
> >>>>  	/* configure 1 or 2 channel mode */
> >>>> 
> >>>> -	ret = vpif_config_data->setup_input_channel_mode
> >>>> -					(vpif->std_info.ycmux_mode);
> >>>> +	if (vpif_config_data->setup_input_channel_mode) {
> >>>> +		ret = vpif_config_data->setup_input_channel_mode
> >>>> +						(vpif->std_info.ycmux_mode);
> >>>> 
> >>>> -	if (ret < 0) {
> >>>> -		vpif_dbg(1, debug, "can't set vpif channel mode\n");
> >>>> -		return ret;
> >>>> +		if (ret < 0) {
> >>>> +			vpif_dbg(1, debug, "can't set vpif channel mode\n");
> >>>> +			return ret;
> >>>> +		}
> >>> 
> >>> This change looks good to me. However, note that you will need to get
> >>> rid of board code callbacks at some point to implement device tree
> >>> support. It would be worth thinking about how to do so now.
> >> 
> >> Currently VPIF driver is only used by dm646x, and the handlers for this
> >> in the the board code are not null. This patch is intended for da850
> >> where this handlers will be null.
> >> 
> >>>>  	}
> >>>>  	
> >>>>  	/* Call vpif_set_params function to set the parameters and addresses
> >>>>  	*/
> >>>> 
> >>>> diff --git a/drivers/media/video/davinci/vpif_display.c
> >>>> b/drivers/media/video/davinci/vpif_display.c index e129c98..1e35f92
> >>>> 100644
> >>>> --- a/drivers/media/video/davinci/vpif_display.c
> >>>> +++ b/drivers/media/video/davinci/vpif_display.c
> >>>> @@ -280,12 +280,14 @@ static int vpif_start_streaming(struct vb2_queue
> >>>> *vq,
> >>>> unsigned int count) }
> >>>> 
> >>>>  	/* clock settings */
> >>>> 
> >>>> -	ret =
> >>>> -	    vpif_config_data->set_clock(ch->vpifparams.std_info.ycmux_mode,
> >>>> -					ch->vpifparams.std_info.hd_sd);
> >>>> -	if (ret < 0) {
> >>>> -		vpif_err("can't set clock\n");
> >>>> -		return ret;
> >>>> +	if (vpif_config_data->set_clock) {
> >>> 
> >>> Does the DaVinci platform use the common clock framework ? If so, a
> >>> better fix for this would be to pass a clock name through platform data
> >>> instead of using a callback function.
> >> 
> >> Currently DaVinci is not using the common clock framework.
> >> 
> >> Can you ACK this patch?
> > 
> > Yes, DaVinci has not migrated to common clock framework (yet). However,
> > even without that it should be possible to use clock API in driver code.
> > Using a callback to enable clocks or even passing the clock name from
> > platform data would be bypassing an existing framework. Clock name
> > should be IP specific, so it should be possible to use that in driver.
> 
> The callback is not actually dealing with PSC clock's but with system
> module registers.

Good to know. Then you'll have to create an API to expose the system module 
registers to drivers.

-- 
Regards,

Laurent Pinchart

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