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

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Date:	Fri, 17 Aug 2012 11:07:13 +0530
From:	Sekhar Nori <nsekhar@...com>
To:	Prabhakar Lad <prabhakar.lad@...com>
CC:	Laurent Pinchart <laurent.pinchart@...asonboard.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>
Subject: Re: [PATCH] media: davinci: vpif: add check for NULL handler

On 8/17/2012 10:51 AM, Prabhakar Lad wrote:
> Hi Laurent,
> 
> Thanks for the review.
> 
> On Thursday 16 August 2012 08:43 PM, Laurent Pinchart wrote:
>> Hi Prabhakar,
>>
>> Thanks for the patch.
>>
>> 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.

Thanks,
Sekhar
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