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Subject: Re: [PATCH AUTOSEL 5.10 14/36] media: rkisp1: uapi: change hist_bins
 array type from __u16 to __u32
To:     Hans Verkuil <hverkuil-cisco@xs4all.nl>,
        Sasha Levin <sashal@kernel.org>, linux-kernel@vger.kernel.org,
        stable@vger.kernel.org
Cc:     Helen Koike <helen.koike@collabora.com>,
        Mauro Carvalho Chehab <mchehab+huawei@kernel.org>,
        linux-media@vger.kernel.org, devel@driverdev.osuosl.org,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>
References: <20210208175806.2091668-1-sashal@kernel.org>
 <20210208175806.2091668-14-sashal@kernel.org>
 <12c8f50e-3bba-5936-6e67-55bd928a75c7@xs4all.nl>
From:   Dafna Hirschfeld <dafna.hirschfeld@collabora.com>
Message-ID: <e086d0f4-c5f0-e38c-8937-593852ac0b50@collabora.com>
Date:   Tue, 9 Feb 2021 13:45:35 +0100
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Am 08.02.21 um 21:46 schrieb Hans Verkuil:
> On 08/02/2021 18:57, Sasha Levin wrote:
>> From: Dafna Hirschfeld <dafna.hirschfeld@collabora.com>
>>
>> [ Upstream commit 31f190e0ccac8b75d33fdc95a797c526cf9b149e ]
>>
>> Each entry in the array is a 20 bits value composed of 16 bits unsigned
>> integer and 4 bits fractional part. So the type should change to __u32.
>> In addition add a documentation of how the measurements are done.
> 
> Dafna, Helen, does it make sense at all to backport these three patches to
> when rkisp1 was a staging driver?
> 
> I would be inclined not to backport this.

I also don't think it makes sense since this changes the uapi and it is not really a bug fix.


Thanks,
Dafna

> 
> Regards,
> 
> 	Hans
> 
>>
>> Signed-off-by: Dafna Hirschfeld <dafna.hirschfeld@collabora.com>
>> Acked-by: Helen Koike <helen.koike@collabora.com>
>> Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
>> Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
>> Signed-off-by: Sasha Levin <sashal@kernel.org>
>> ---
>>   drivers/staging/media/rkisp1/uapi/rkisp1-config.h | 13 +++++++++----
>>   1 file changed, 9 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/staging/media/rkisp1/uapi/rkisp1-config.h b/drivers/staging/media/rkisp1/uapi/rkisp1-config.h
>> index 432cb6be55b47..c19fe059c2442 100644
>> --- a/drivers/staging/media/rkisp1/uapi/rkisp1-config.h
>> +++ b/drivers/staging/media/rkisp1/uapi/rkisp1-config.h
>> @@ -848,13 +848,18 @@ struct rkisp1_cif_isp_af_stat {
>>   /**
>>    * struct rkisp1_cif_isp_hist_stat - statistics histogram data
>>    *
>> - * @hist_bins: measured bin counters
>> + * @hist_bins: measured bin counters. Each bin is a 20 bits unsigned fixed point
>> + *	       type. Bits 0-4 are the fractional part and bits 5-19 are the
>> + *	       integer part.
>>    *
>> - * Measurement window divided into 25 sub-windows, set
>> - * with ISP_HIST_XXX
>> + * The window of the measurements area is divided to 5x5 sub-windows. The
>> + * histogram is then computed for each sub-window independently and the final
>> + * result is a weighted average of the histogram measurements on all
>> + * sub-windows. The window of the measurements area and the weight of each
>> + * sub-window are configurable using struct @rkisp1_cif_isp_hst_config.
>>    */
>>   struct rkisp1_cif_isp_hist_stat {
>> -	__u16 hist_bins[RKISP1_CIF_ISP_HIST_BIN_N_MAX];
>> +	__u32 hist_bins[RKISP1_CIF_ISP_HIST_BIN_N_MAX];
>>   };
>>   
>>   /**
>>
>